diff options
Diffstat (limited to 'Documentation/gpu')
| -rw-r--r-- | Documentation/gpu/drm-internals.rst | 65 | ||||
| -rw-r--r-- | Documentation/gpu/drm-kms-helpers.rst | 40 | ||||
| -rw-r--r-- | Documentation/gpu/drm-kms.rst | 264 | ||||
| -rw-r--r-- | Documentation/gpu/drm-mm.rst | 41 | ||||
| -rw-r--r-- | Documentation/gpu/drm-uapi.rst | 4 | ||||
| -rw-r--r-- | Documentation/gpu/i915.rst | 9 | ||||
| -rw-r--r-- | Documentation/gpu/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/gpu/introduction.rst | 10 | ||||
| -rw-r--r-- | Documentation/gpu/todo.rst | 334 | ||||
| -rw-r--r-- | Documentation/gpu/vc4.rst | 89 |
10 files changed, 756 insertions, 102 deletions
diff --git a/Documentation/gpu/drm-internals.rst b/Documentation/gpu/drm-internals.rst index e35920db1f4c..a09c721f9e89 100644 --- a/Documentation/gpu/drm-internals.rst +++ b/Documentation/gpu/drm-internals.rst @@ -140,12 +140,12 @@ Device Instance and Driver Handling .. kernel-doc:: drivers/gpu/drm/drm_drv.c :doc: driver instance overview -.. kernel-doc:: drivers/gpu/drm/drm_drv.c - :export: - .. kernel-doc:: include/drm/drm_drv.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_drv.c + :export: + Driver Load ----------- @@ -240,68 +240,19 @@ drivers. .. kernel-doc:: drivers/gpu/drm/drm_pci.c :export: -.. kernel-doc:: drivers/gpu/drm/drm_platform.c - :export: - Open/Close, File Operations and IOCTLs ====================================== -Open and Close --------------- - -Open and close handlers. None of those methods are mandatory:: - - int (*firstopen) (struct drm_device *); - void (*lastclose) (struct drm_device *); - int (*open) (struct drm_device *, struct drm_file *); - void (*preclose) (struct drm_device *, struct drm_file *); - void (*postclose) (struct drm_device *, struct drm_file *); - -The firstopen method is called by the DRM core for legacy UMS (User Mode -Setting) drivers only when an application opens a device that has no -other opened file handle. UMS drivers can implement it to acquire device -resources. KMS drivers can't use the method and must acquire resources -in the load method instead. - -Similarly the lastclose method is called when the last application -holding a file handle opened on the device closes it, for both UMS and -KMS drivers. Additionally, the method is also called at module unload -time or, for hot-pluggable devices, when the device is unplugged. The -firstopen and lastclose calls can thus be unbalanced. - -The open method is called every time the device is opened by an -application. Drivers can allocate per-file private data in this method -and store them in the struct :c:type:`struct drm_file -<drm_file>` driver_priv field. Note that the open method is -called before firstopen. - -The close operation is split into preclose and postclose methods. -Drivers must stop and cleanup all per-file operations in the preclose -method. For instance pending vertical blanking and page flip events must -be cancelled. No per-file operation is allowed on the file handle after -returning from the preclose method. - -Finally the postclose method is called as the last step of the close -operation, right before calling the lastclose method if no other open -file handle exists for the device. Drivers that have allocated per-file -private data in the open method should free it here. - -The lastclose method should restore CRTC and plane properties to default -value, so that a subsequent open of the device will not inherit state -from the previous user. It can also be used to execute delayed power -switching state changes, e.g. in conjunction with the :ref:`vga_switcheroo` -infrastructure. Beyond that KMS drivers should not do any -further cleanup. Only legacy UMS drivers might need to clean up device -state so that the vga console or an independent fbdev driver could take -over. - File Operations --------------- -.. kernel-doc:: drivers/gpu/drm/drm_fops.c +.. kernel-doc:: drivers/gpu/drm/drm_file.c :doc: file operations -.. kernel-doc:: drivers/gpu/drm/drm_fops.c +.. kernel-doc:: include/drm/drm_file.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_file.c :export: IOCTLs diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst index 03040aa14fe8..c075aadd7078 100644 --- a/Documentation/gpu/drm-kms-helpers.rst +++ b/Documentation/gpu/drm-kms-helpers.rst @@ -37,10 +37,12 @@ Modeset Helper Reference for Common Vtables =========================================== .. kernel-doc:: include/drm/drm_modeset_helper_vtables.h - :internal: + :doc: overview .. kernel-doc:: include/drm/drm_modeset_helper_vtables.h - :doc: overview + :internal: + +.. _drm_atomic_helper: Atomic Modeset Helper Functions Reference ========================================= @@ -84,27 +86,27 @@ Legacy CRTC/Modeset Helper Functions Reference Simple KMS Helper Reference =========================== +.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c + :doc: overview + .. kernel-doc:: include/drm/drm_simple_kms_helper.h :internal: .. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c :export: -.. kernel-doc:: drivers/gpu/drm/drm_simple_kms_helper.c - :doc: overview - fbdev Helper Functions Reference ================================ .. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c :doc: fbdev helpers -.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c - :export: - .. kernel-doc:: include/drm/drm_fb_helper.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_fb_helper.c + :export: + Framebuffer CMA Helper Functions Reference ========================================== @@ -114,6 +116,8 @@ Framebuffer CMA Helper Functions Reference .. kernel-doc:: drivers/gpu/drm/drm_fb_cma_helper.c :export: +.. _drm_bridges: + Bridges ======= @@ -139,18 +143,20 @@ Bridge Helper Reference .. kernel-doc:: drivers/gpu/drm/drm_bridge.c :export: +.. _drm_panel_helper: + Panel Helper Reference ====================== +.. kernel-doc:: drivers/gpu/drm/drm_panel.c + :doc: drm panel + .. kernel-doc:: include/drm/drm_panel.h :internal: .. kernel-doc:: drivers/gpu/drm/drm_panel.c :export: -.. kernel-doc:: drivers/gpu/drm/drm_panel.c - :doc: drm panel - Display Port Helper Functions Reference ======================================= @@ -217,6 +223,18 @@ EDID Helper Functions Reference .. kernel-doc:: drivers/gpu/drm/drm_edid.c :export: +SCDC Helper Functions Reference +=============================== + +.. kernel-doc:: drivers/gpu/drm/drm_scdc_helper.c + :doc: scdc helpers + +.. kernel-doc:: include/drm/drm_scdc_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_scdc_helper.c + :export: + Rectangle Utilities Reference ============================= diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 4d4068855ec4..bfecd21a8cdf 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -15,35 +15,271 @@ be setup by initializing the following fields. - struct drm_mode_config_funcs \*funcs; Mode setting functions. -Mode Configuration +Overview +======== + +.. kernel-render:: DOT + :alt: KMS Display Pipeline + :caption: KMS Display Pipeline Overview + + digraph "KMS" { + node [shape=box] + + subgraph cluster_static { + style=dashed + label="Static Objects" + + node [bgcolor=grey style=filled] + "drm_plane A" -> "drm_crtc" + "drm_plane B" -> "drm_crtc" + "drm_crtc" -> "drm_encoder A" + "drm_crtc" -> "drm_encoder B" + } + + subgraph cluster_user_created { + style=dashed + label="Userspace-Created" + + node [shape=oval] + "drm_framebuffer 1" -> "drm_plane A" + "drm_framebuffer 2" -> "drm_plane B" + } + + subgraph cluster_connector { + style=dashed + label="Hotpluggable" + + "drm_encoder A" -> "drm_connector A" + "drm_encoder B" -> "drm_connector B" + } + } + +The basic object structure KMS presents to userspace is fairly simple. +Framebuffers (represented by :c:type:`struct drm_framebuffer <drm_framebuffer>`, +see `Frame Buffer Abstraction`_) feed into planes. One or more (or even no) +planes feed their pixel data into a CRTC (represented by :c:type:`struct +drm_crtc <drm_crtc>`, see `CRTC Abstraction`_) for blending. The precise +blending step is explained in more detail in `Plane Composition Properties`_ and +related chapters. + +For the output routing the first step is encoders (represented by +:c:type:`struct drm_encoder <drm_encoder>`, see `Encoder Abstraction`_). Those +are really just internal artifacts of the helper libraries used to implement KMS +drivers. Besides that they make it unecessarily more complicated for userspace +to figure out which connections between a CRTC and a connector are possible, and +what kind of cloning is supported, they serve no purpose in the userspace API. +Unfortunately encoders have been exposed to userspace, hence can't remove them +at this point. Futhermore the exposed restrictions are often wrongly set by +drivers, and in many cases not powerful enough to express the real restrictions. +A CRTC can be connected to multiple encoders, and for an active CRTC there must +be at least one encoder. + +The final, and real, endpoint in the display chain is the connector (represented +by :c:type:`struct drm_connector <drm_connector>`, see `Connector +Abstraction`_). Connectors can have different possible encoders, but the kernel +driver selects which encoder to use for each connector. The use case is DVI, +which could switch between an analog and a digital encoder. Encoders can also +drive multiple different connectors. There is exactly one active connector for +every active encoder. + +Internally the output pipeline is a bit more complex and matches today's +hardware more closely: + +.. kernel-render:: DOT + :alt: KMS Output Pipeline + :caption: KMS Output Pipeline + + digraph "Output Pipeline" { + node [shape=box] + + subgraph { + "drm_crtc" [bgcolor=grey style=filled] + } + + subgraph cluster_internal { + style=dashed + label="Internal Pipeline" + { + node [bgcolor=grey style=filled] + "drm_encoder A"; + "drm_encoder B"; + "drm_encoder C"; + } + + { + node [bgcolor=grey style=filled] + "drm_encoder B" -> "drm_bridge B" + "drm_encoder C" -> "drm_bridge C1" + "drm_bridge C1" -> "drm_bridge C2"; + } + } + + "drm_crtc" -> "drm_encoder A" + "drm_crtc" -> "drm_encoder B" + "drm_crtc" -> "drm_encoder C" + + + subgraph cluster_output { + style=dashed + label="Outputs" + + "drm_encoder A" -> "drm_connector A"; + "drm_bridge B" -> "drm_connector B"; + "drm_bridge C2" -> "drm_connector C"; + + "drm_panel" + } + } + +Internally two additional helper objects come into play. First, to be able to +share code for encoders (sometimes on the same SoC, sometimes off-chip) one or +more :ref:`drm_bridges` (represented by :c:type:`struct drm_bridge +<drm_bridge>`) can be linked to an encoder. This link is static and cannot be +changed, which means the cross-bar (if there is any) needs to be mapped between +the CRTC and any encoders. Often for drivers with bridges there's no code left +at the encoder level. Atomic drivers can leave out all the encoder callbacks to +essentially only leave a dummy routing object behind, which is needed for +backwards compatibility since encoders are exposed to userspace. + +The second object is for panels, represented by :c:type:`struct drm_panel +<drm_panel>`, see :ref:`drm_panel_helper`. Panels do not have a fixed binding +point, but are generally linked to the driver private structure that embeds +:c:type:`struct drm_connector <drm_connector>`. + +Note that currently the bridge chaining and interactions with connectors and +panels are still in-flux and not really fully sorted out yet. KMS Core Structures and Functions ================================= -.. kernel-doc:: drivers/gpu/drm/drm_mode_config.c - :export: - .. kernel-doc:: include/drm/drm_mode_config.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_mode_config.c + :export: + Modeset Base Object Abstraction =============================== +.. kernel-render:: DOT + :alt: Mode Objects and Properties + :caption: Mode Objects and Properties + + digraph { + node [shape=box] + + "drm_property A" -> "drm_mode_object A" + "drm_property A" -> "drm_mode_object B" + "drm_property B" -> "drm_mode_object A" + } + +The base structure for all KMS objects is :c:type:`struct drm_mode_object +<drm_mode_object>`. One of the base services it provides is tracking properties, +which are especially important for the atomic IOCTL (see `Atomic Mode +Setting`_). The somewhat surprising part here is that properties are not +directly instantiated on each object, but free-standing mode objects themselves, +represented by :c:type:`struct drm_property <drm_property>`, which only specify +the type and value range of a property. Any given property can be attached +multiple times to different objects using :c:func:`drm_object_attach_property() +<drm_object_attach_property>`. + .. kernel-doc:: include/drm/drm_mode_object.h :internal: .. kernel-doc:: drivers/gpu/drm/drm_mode_object.c :export: -Atomic Mode Setting Function Reference -====================================== +Atomic Mode Setting +=================== -.. kernel-doc:: drivers/gpu/drm/drm_atomic.c - :export: + +.. kernel-render:: DOT + :alt: Mode Objects and Properties + :caption: Mode Objects and Properties + + digraph { + node [shape=box] + + subgraph cluster_state { + style=dashed + label="Free-standing state" + + "drm_atomic_state" -> "duplicated drm_plane_state A" + "drm_atomic_state" -> "duplicated drm_plane_state B" + "drm_atomic_state" -> "duplicated drm_crtc_state" + "drm_atomic_state" -> "duplicated drm_connector_state" + "drm_atomic_state" -> "duplicated driver private state" + } + + subgraph cluster_current { + style=dashed + label="Current state" + + "drm_device" -> "drm_plane A" + "drm_device" -> "drm_plane B" + "drm_device" -> "drm_crtc" + "drm_device" -> "drm_connector" + "drm_device" -> "driver private object" + + "drm_plane A" -> "drm_plane_state A" + "drm_plane B" -> "drm_plane_state B" + "drm_crtc" -> "drm_crtc_state" + "drm_connector" -> "drm_connector_state" + "driver private object" -> "driver private state" + } + + "drm_atomic_state" -> "drm_device" [label="atomic_commit"] + "duplicated drm_plane_state A" -> "drm_device"[style=invis] + } + +Atomic provides transactional modeset (including planes) updates, but a +bit differently from the usual transactional approach of try-commit and +rollback: + +- Firstly, no hardware changes are allowed when the commit would fail. This + allows us to implement the DRM_MODE_ATOMIC_TEST_ONLY mode, which allows + userspace to explore whether certain configurations would work or not. + +- This would still allow setting and rollback of just the software state, + simplifying conversion of existing drivers. But auditing drivers for + correctness of the atomic_check code becomes really hard with that: Rolling + back changes in data structures all over the place is hard to get right. + +- Lastly, for backwards compatibility and to support all use-cases, atomic + updates need to be incremental and be able to execute in parallel. Hardware + doesn't always allow it, but where possible plane updates on different CRTCs + should not interfere, and not get stalled due to output routing changing on + different CRTCs. + +Taken all together there's two consequences for the atomic design: + +- The overall state is split up into per-object state structures: + :c:type:`struct drm_plane_state <drm_plane_state>` for planes, :c:type:`struct + drm_crtc_state <drm_crtc_state>` for CRTCs and :c:type:`struct + drm_connector_state <drm_connector_state>` for connectors. These are the only + objects with userspace-visible and settable state. For internal state drivers + can subclass these structures through embeddeding, or add entirely new state + structures for their globally shared hardware functions. + +- An atomic update is assembled and validated as an entirely free-standing pile + of structures within the :c:type:`drm_atomic_state <drm_atomic_state>` + container. Again drivers can subclass that container for their own state + structure tracking needs. Only when a state is committed is it applied to the + driver and modeset objects. This way rolling back an update boils down to + releasing memory and unreferencing objects like framebuffers. + +Read on in this chapter, and also in :ref:`drm_atomic_helper` for more detailed +coverage of specific topics. + +Atomic Mode Setting Function Reference +-------------------------------------- .. kernel-doc:: include/drm/drm_atomic.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_atomic.c + :export: + CRTC Abstraction ================ @@ -68,12 +304,12 @@ Frame Buffer Abstraction Frame Buffer Functions Reference -------------------------------- -.. kernel-doc:: drivers/gpu/drm/drm_framebuffer.c - :export: - .. kernel-doc:: include/drm/drm_framebuffer.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_framebuffer.c + :export: + DRM Format Handling =================== @@ -376,8 +612,8 @@ operation handler. Vertical Blanking and Interrupt Handling Functions Reference ------------------------------------------------------------ -.. kernel-doc:: drivers/gpu/drm/drm_irq.c - :export: - .. kernel-doc:: include/drm/drm_irq.h :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_irq.c + :export: diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst index f5760b140f13..96b9c34c21e4 100644 --- a/Documentation/gpu/drm-mm.rst +++ b/Documentation/gpu/drm-mm.rst @@ -183,14 +183,12 @@ GEM Objects Lifetime -------------------- All GEM objects are reference-counted by the GEM core. References can be -acquired and release by :c:func:`calling -drm_gem_object_reference()` and -:c:func:`drm_gem_object_unreference()` respectively. The caller -must hold the :c:type:`struct drm_device <drm_device>` -struct_mutex lock when calling -:c:func:`drm_gem_object_reference()`. As a convenience, GEM -provides :c:func:`drm_gem_object_unreference_unlocked()` -functions that can be called without holding the lock. +acquired and release by :c:func:`calling drm_gem_object_get()` and +:c:func:`drm_gem_object_put()` respectively. The caller must hold the +:c:type:`struct drm_device <drm_device>` struct_mutex lock when calling +:c:func:`drm_gem_object_get()`. As a convenience, GEM provides +:c:func:`drm_gem_object_put_unlocked()` functions that can be called without +holding the lock. When the last reference to a GEM object is released the GEM core calls the :c:type:`struct drm_driver <drm_driver>` gem_free_object @@ -367,36 +365,36 @@ from the client in libdrm. GEM Function Reference ---------------------- -.. kernel-doc:: drivers/gpu/drm/drm_gem.c - :export: - .. kernel-doc:: include/drm/drm_gem.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_gem.c + :export: + GEM CMA Helper Functions Reference ---------------------------------- .. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c :doc: cma helpers -.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c - :export: - .. kernel-doc:: include/drm/drm_gem_cma_helper.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_gem_cma_helper.c + :export: + VMA Offset Manager ================== .. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c :doc: vma offset manager -.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c - :export: - .. kernel-doc:: include/drm/drm_vma_manager.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_vma_manager.c + :export: + PRIME Buffer Sharing ==================== @@ -451,6 +449,9 @@ PRIME Helper Functions PRIME Function References ------------------------- +.. kernel-doc:: include/drm/drm_prime.h + :internal: + .. kernel-doc:: drivers/gpu/drm/drm_prime.c :export: @@ -472,12 +473,12 @@ LRU Scan/Eviction Support DRM MM Range Allocator Function References ------------------------------------------ -.. kernel-doc:: drivers/gpu/drm/drm_mm.c - :export: - .. kernel-doc:: include/drm/drm_mm.h :internal: +.. kernel-doc:: drivers/gpu/drm/drm_mm.c + :export: + DRM Cache Handling ================== diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index fcc228ef5bc4..352652810dab 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -21,6 +21,8 @@ libdrm Device Lookup :doc: getunique and setversion story +.. _drm_primary_node: + Primary Nodes, DRM Master and Authentication ============================================ @@ -103,6 +105,8 @@ is already rather painful for the DRM subsystem, with multiple different uAPIs for the same thing co-existing. If we add a few more complete mistakes into the mix every year it would be entirely unmanageable. +.. _drm_render_node: + Render nodes ============ diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst index b0d6709b8600..9c7ed3e3f1e9 100644 --- a/Documentation/gpu/i915.rst +++ b/Documentation/gpu/i915.rst @@ -222,6 +222,15 @@ Video BIOS Table (VBT) .. kernel-doc:: drivers/gpu/drm/i915/intel_vbt_defs.h :internal: +Display clocks +-------------- + +.. kernel-doc:: drivers/gpu/drm/i915/intel_cdclk.c + :doc: CDCLK / RAWCLK + +.. kernel-doc:: drivers/gpu/drm/i915/intel_cdclk.c + :internal: + Display PLLs ------------ diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst index f81278a7c2cc..e998ee0d0dd5 100644 --- a/Documentation/gpu/index.rst +++ b/Documentation/gpu/index.rst @@ -12,8 +12,10 @@ Linux GPU Driver Developer's Guide drm-uapi i915 tinydrm + vc4 vga-switcheroo vgaarbiter + todo .. only:: subproject and html diff --git a/Documentation/gpu/introduction.rst b/Documentation/gpu/introduction.rst index eb284eb748ba..1f8bd5ef5f9d 100644 --- a/Documentation/gpu/introduction.rst +++ b/Documentation/gpu/introduction.rst @@ -50,3 +50,13 @@ names are "Notes" with information for dangerous or tricky corner cases, and "FIXME" where the interface could be cleaned up. Also read the :ref:`guidelines for the kernel documentation at large <doc_guide>`. + +Getting Started +=============== + +Developers interested in helping out with the DRM subsystem are very welcome. +Often people will resort to sending in patches for various issues reported by +checkpatch or sparse. We welcome such contributions. + +Anyone looking to kick it up a notch can find a list of janitorial tasks on +the :ref:`TODO list <todo>`. diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst new file mode 100644 index 000000000000..64e9d16170ce --- /dev/null +++ b/Documentation/gpu/todo.rst @@ -0,0 +1,334 @@ +.. _todo: + +========= +TODO list +========= + +This section contains a list of smaller janitorial tasks in the kernel DRM +graphics subsystem useful as newbie projects. Or for slow rainy days. + +Subsystem-wide refactorings +=========================== + +De-midlayer drivers +------------------- + +With the recent ``drm_bus`` cleanup patches for 3.17 it is no longer required +to have a ``drm_bus`` structure set up. Drivers can directly set up the +``drm_device`` structure instead of relying on bus methods in ``drm_usb.c`` +and ``drm_platform.c``. The goal is to get rid of the driver's ``->load`` / +``->unload`` callbacks and open-code the load/unload sequence properly, using +the new two-stage ``drm_device`` setup/teardown. + +Once all existing drivers are converted we can also remove those bus support +files for USB and platform devices. + +All you need is a GPU for a non-converted driver (currently almost all of +them, but also all the virtual ones used by KVM, so everyone qualifies). + +Contact: Daniel Vetter, Thierry Reding, respective driver maintainers + +Switch from reference/unreference to get/put +-------------------------------------------- + +For some reason DRM core uses ``reference``/``unreference`` suffixes for +refcounting functions, but kernel uses ``get``/``put`` (e.g. +``kref_get``/``put()``). It would be good to switch over for consistency, and +it's shorter. Needs to be done in 3 steps for each pair of functions: + +* Create new ``get``/``put`` functions, define the old names as compatibility + wrappers +* Switch over each file/driver using a cocci-generated spatch. +* Once all users of the old names are gone, remove them. + +This way drivers/patches in the progress of getting merged won't break. + +Contact: Daniel Vetter + +Convert existing KMS drivers to atomic modesetting +-------------------------------------------------- + +3.19 has the atomic modeset interfaces and helpers, so drivers can now be +converted over. Modern compositors like Wayland or Surfaceflinger on Android +really want an atomic modeset interface, so this is all about the bright +future. + +There is a conversion guide for atomic and all you need is a GPU for a +non-converted driver (again virtual HW drivers for KVM are still all +suitable). + +As part of this drivers also need to convert to universal plane (which means +exposing primary & cursor as proper plane objects). But that's much easier to +do by directly using the new atomic helper driver callbacks. + +Contact: Daniel Vetter, respective driver maintainers + +Clean up the clipped coordination confusion around planes +--------------------------------------------------------- + +We have a helper to get this right with drm_plane_helper_check_update(), but +it's not consistently used. This should be fixed, preferrably in the atomic +helpers (and drivers then moved over to clipped coordinates). Probably the +helper should also be moved from drm_plane_helper.c to the atomic helpers, to +avoid confusion - the other helpers in that file are all deprecated legacy +helpers. + +Contact: Ville Syrjälä, Daniel Vetter, driver maintainers + +Implement deferred fbdev setup in the helper +-------------------------------------------- + +Many (especially embedded drivers) want to delay fbdev setup until there's a +real screen plugged in. This is to avoid the dreaded fallback to the low-res +fbdev default. Many drivers have a hacked-up (and often broken) version of this, +better to do it once in the shared helpers. Thierry has a patch series, but that +one needs to be rebased and final polish applied. + +Contact: Thierry Reding, Daniel Vetter, driver maintainers + +Convert early atomic drivers to async commit helpers +---------------------------------------------------- + +For the first year the atomic modeset helpers didn't support asynchronous / +nonblocking commits, and every driver had to hand-roll them. This is fixed +now, but there's still a pile of existing drivers that easily could be +converted over to the new infrastructure. + +One issue with the helpers is that they require that drivers handle completion +events for atomic commits correctly. But fixing these bugs is good anyway. + +Contact: Daniel Vetter, respective driver maintainers + +Fallout from atomic KMS +----------------------- + +``drm_atomic_helper.c`` provides a batch of functions which implement legacy +IOCTLs on top of the new atomic driver interface. Which is really nice for +gradual conversion of drivers, but unfortunately the semantic mismatches are +a bit too severe. So there's some follow-up work to adjust the function +interfaces to fix these issues: + +* atomic needs the lock acquire context. At the moment that's passed around + implicitly with some horrible hacks, and it's also allocate with + ``GFP_NOFAIL`` behind the scenes. All legacy paths need to start allocating + the acquire context explicitly on stack and then also pass it down into + drivers explicitly so that the legacy-on-atomic functions can use them. + +* A bunch of the vtable hooks are now in the wrong place: DRM has a split + between core vfunc tables (named ``drm_foo_funcs``), which are used to + implement the userspace ABI. And then there's the optional hooks for the + helper libraries (name ``drm_foo_helper_funcs``), which are purely for + internal use. Some of these hooks should be move from ``_funcs`` to + ``_helper_funcs`` since they are not part of the core ABI. There's a + ``FIXME`` comment in the kerneldoc for each such case in ``drm_crtc.h``. + +* There's a new helper ``drm_atomic_helper_best_encoder()`` which could be + used by all atomic drivers which don't select the encoder for a given + connector at runtime. That's almost all of them, and would allow us to get + rid of a lot of ``best_encoder`` boilerplate in drivers. + +Contact: Daniel Vetter + +Get rid of dev->struct_mutex from GEM drivers +--------------------------------------------- + +``dev->struct_mutex`` is the Big DRM Lock from legacy days and infested +everything. Nowadays in modern drivers the only bit where it's mandatory is +serializing GEM buffer object destruction. Which unfortunately means drivers +have to keep track of that lock and either call ``unreference`` or +``unreference_locked`` depending upon context. + +Core GEM doesn't have a need for ``struct_mutex`` any more since kernel 4.8, +and there's a ``gem_free_object_unlocked`` callback for any drivers which are +entirely ``struct_mutex`` free. + +For drivers that need ``struct_mutex`` it should be replaced with a driver- +private lock. The tricky part is the BO free functions, since those can't +reliably take that lock any more. Instead state needs to be protected with +suitable subordinate locks or some cleanup work pushed to a worker thread. For +performance-critical drivers it might also be better to go with a more +fine-grained per-buffer object and per-context lockings scheme. Currently the +following drivers still use ``struct_mutex``: ``msm``, ``omapdrm`` and +``udl``. + +Contact: Daniel Vetter + +Switch to drm_connector_list_iter for any connector_list walking +---------------------------------------------------------------- + +Connectors can be hotplugged, and we now have a special list of helpers to walk +the connector_list in a race-free fashion, without incurring deadlocks on +mutexes and other fun stuff. + +Unfortunately most drivers are not converted yet. At least all those supporting +DP MST hotplug should be converted, since for those drivers the difference +matters. See drm_for_each_connector_iter() vs. drm_for_each_connector(). + +Contact: Daniel Vetter + +Core refactorings +================= + +Use new IDR deletion interface to clean up drm_gem_handle_delete() +------------------------------------------------------------------ + +See the "This is gross" comment -- apparently the IDR system now can return an +error code instead of oopsing. + +Clean up the DRM header mess +---------------------------- + +Currently the DRM subsystem has only one global header, ``drmP.h``. This is +used both for functions exported to helper libraries and drivers and functions +only used internally in the ``drm.ko`` module. The goal would be to move all +header declarations not needed outside of ``drm.ko`` into +``drivers/gpu/drm/drm_*_internal.h`` header files. ``EXPORT_SYMBOL`` also +needs to be dropped for these functions. + +This would nicely tie in with the below task to create kerneldoc after the API +is cleaned up. Or with the "hide legacy cruft better" task. + +Note that this is well in progress, but ``drmP.h`` is still huge. The updated +plan is to switch to per-file driver API headers, which will also structure +the kerneldoc better. This should also allow more fine-grained ``#include`` +directives. + +Contact: Daniel Vetter + +Add missing kerneldoc for exported functions +-------------------------------------------- + +The DRM reference documentation is still lacking kerneldoc in a few areas. The +task would be to clean up interfaces like moving functions around between +files to better group them and improving the interfaces like dropping return +values for functions that never fail. Then write kerneldoc for all exported +functions and an overview section and integrate it all into the drm DocBook. + +See https://dri.freedesktop.org/docs/drm/ for what's there already. + +Contact: Daniel Vetter + +Hide legacy cruft better +------------------------ + +Way back DRM supported only drivers which shadow-attached to PCI devices with +userspace or fbdev drivers setting up outputs. Modern DRM drivers take charge +of the entire device, you can spot them with the DRIVER_MODESET flag. + +Unfortunately there's still large piles of legacy code around which needs to +be hidden so that driver writers don't accidentally end up using it. And to +prevent security issues in those legacy IOCTLs from being exploited on modern +drivers. This has multiple possible subtasks: + +* Make sure legacy IOCTLs can't be used on modern drivers. +* Extract support code for legacy features into a ``drm-legacy.ko`` kernel + module and compile it only when one of the legacy drivers is enabled. +* Extract legacy functions into their own headers and remove it that from the + monolithic ``drmP.h`` header. +* Remove any lingering cruft from the OS abstraction layer from modern + drivers. + +This is mostly done, the only thing left is to split up ``drm_irq.c`` into +legacy cruft and the parts needed by modern KMS drivers. + +Contact: Daniel Vetter + +Make panic handling work +------------------------ + +This is a really varied tasks with lots of little bits and pieces: + +* The panic path can't be tested currently, leading to constant breaking. The + main issue here is that panics can be triggered from hardirq contexts and + hence all panic related callback can run in hardirq context. It would be + awesome if we could test at least the fbdev helper code and driver code by + e.g. trigger calls through drm debugfs files. hardirq context could be + achieved by using an IPI to the local processor. + +* There's a massive confusion of different panic handlers. DRM fbdev emulation + helpers have one, but on top of that the fbcon code itself also has one. We + need to make sure that they stop fighting over each another. + +* ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and + isn't a full solution for panic paths. We need to make sure that it only + returns true if there's a panic going on for real, and fix up all the + fallout. + +* The panic handler must never sleep, which also means it can't ever + ``mutex_lock()``. Also it can't grab any other lock unconditionally, not + even spinlocks (because NMI and hardirq can panic too). We need to either + make sure to not call such paths, or trylock everything. Really tricky. + +* For the above locking troubles reasons it's pretty much impossible to + attempt a synchronous modeset from panic handlers. The only thing we could + try to achive is an atomic ``set_base`` of the primary plane, and hope that + it shows up. Everything else probably needs to be delayed to some worker or + something else which happens later on. Otherwise it just kills the box + harder, prevent the panic from going out on e.g. netconsole. + +* There's also proposal for a simplied DRM console instead of the full-blown + fbcon and DRM fbdev emulation. Any kind of panic handling tricks should + obviously work for both console, in case we ever get kmslog merged. + +Contact: Daniel Vetter + +Better Testing +============== + +Enable trinity for DRM +---------------------- + +And fix up the fallout. Should be really interesting ... + +Make KMS tests in i-g-t generic +------------------------------- + +The i915 driver team maintains an extensive testsuite for the i915 DRM driver, +including tons of testcases for corner-cases in the modesetting API. It would +be awesome if those tests (at least the ones not relying on Intel-specific GEM +features) could be made to run on any KMS driver. + +Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass- +converting things over. For modeset tests we also first need a bit of +infrastructure to use dumb buffers for untiled buffers, to be able to run all +the non-i915 specific modeset tests. + +Contact: Daniel Vetter + +Create a virtual KMS driver for testing (vkms) +---------------------------------------------- + +With all the latest helpers it should be fairly simple to create a virtual KMS +driver useful for testing, or for running X or similar on headless machines +(to be able to still use the GPU). This would be similar to vgem, but aimed at +the modeset side. + +Once the basics are there there's tons of possibilities to extend it. + +Contact: Daniel Vetter + +Driver Specific +=============== + +Outside DRM +=========== + +Better kerneldoc +---------------- + +This is pretty much done, but there's some advanced topics: + +Come up with a way to hyperlink to struct members. Currently you can hyperlink +to the struct using ``#struct_name``, but not to a member within. Would need +buy-in from kerneldoc maintainers, and the big question is how to make it work +without totally unsightly +``drm_foo_bar_really_long_structure->even_longer_memeber`` all over the text +which breaks text flow. + +Figure out how to integrate the asciidoc support for ascii-diagrams. We have a +few of those (e.g. to describe mode timings), and asciidoc supports converting +some ascii-art dialect into pngs. Would be really pretty to make that work. + +Contact: Daniel Vetter, Jani Nikula + +Jani is working on this already, hopefully lands in 4.8. diff --git a/Documentation/gpu/vc4.rst b/Documentation/gpu/vc4.rst new file mode 100644 index 000000000000..5df1d98b9544 --- /dev/null +++ b/Documentation/gpu/vc4.rst @@ -0,0 +1,89 @@ +===================================== + drm/vc4 Broadcom VC4 Graphics Driver +===================================== + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_drv.c + :doc: Broadcom VC4 Graphics Driver + +Display Hardware Handling +========================= + +This section covers everything related to the display hardware including +the mode setting infrastructure, plane, sprite and cursor handling and +display, output probing and related topics. + +Pixel Valve (DRM CRTC) +---------------------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_crtc.c + :doc: VC4 CRTC module + +HVS +--- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_hvs.c + :doc: VC4 HVS module. + +HVS planes +---------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_plane.c + :doc: VC4 plane module + +HDMI encoder +------------ + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_hdmi.c + :doc: VC4 Falcon HDMI module + +DSI encoder +----------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_dsi.c + :doc: VC4 DSI0/DSI1 module + +DPI encoder +----------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_dpi.c + :doc: VC4 DPI module + +VEC (Composite TV out) encoder +------------------------------ + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_vec.c + :doc: VC4 SDTV module + +Memory Management and 3D Command Submission +=========================================== + +This section covers the GEM implementation in the vc4 driver. + +GPU buffer object (BO) management +--------------------------------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_bo.c + :doc: VC4 GEM BO management support + +V3D binner command list (BCL) validation +---------------------------------------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_validate.c + :doc: Command list validator for VC4. + +V3D render command list (RCL) generation +---------------------------------------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_render_cl.c + :doc: Render command list generation + +Shader validator for VC4 +--------------------------- +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_validate_shaders.c + :doc: Shader validator for VC4. + +V3D Interrupts +-------------- + +.. kernel-doc:: drivers/gpu/drm/vc4/vc4_irq.c + :doc: Interrupt management for the V3D engine |