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-rw-r--r--Documentation/gpu/todo.rst47
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diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 7bf7f2111696..127e76ee0b2d 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -241,6 +241,28 @@ Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
Level: Advanced
+Benchmark and optimize blitting and format-conversion function
+--------------------------------------------------------------
+
+Drawing to dispay memory quickly is crucial for many applications'
+performance.
+
+On at least x86-64, sys_imageblit() is significantly slower than
+cfb_imageblit(), even though both use the same blitting algorithm and
+the latter is written for I/O memory. It turns out that cfb_imageblit()
+uses movl instructions, while sys_imageblit apparently does not. This
+seems to be a problem with gcc's optimizer. DRM's format-conversion
+helpers might be subject to similar issues.
+
+Benchmark and optimize fbdev's sys_() helpers and DRM's format-conversion
+helpers. In cases that can be further optimized, maybe implement a different
+algorithm. For micro-optimizations, use movl/movq instructions explicitly.
+That might possibly require architecture-specific helpers (e.g., storel()
+storeq()).
+
+Contact: Thomas Zimmermann <tzimmermann@suse.de>
+
+Level: Intermediate
drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
-----------------------------------------------------------------
@@ -475,8 +497,12 @@ This is a really varied tasks with lots of little bits and pieces:
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.
+ helpers had their own (long removed), but on top of that the fbcon code itself
+ also has one. We need to make sure that they stop fighting over each other.
+ This is worked around by checking ``oops_in_progress`` at various entry points
+ into the DRM fbdev emulation helpers. A much cleaner approach here would be to
+ switch fbcon to the `threaded printk support
+ <https://lwn.net/Articles/800946/>`_.
* ``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
@@ -488,16 +514,15 @@ This is a really varied tasks with lots of little bits and pieces:
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.
+* A clean solution would be an entirely separate panic output support in KMS,
+ bypassing the current fbcon support. See `[PATCH v2 0/3] drm: Add panic handling
+ <https://lore.kernel.org/dri-devel/20190311174218.51899-1-noralf@tronnes.org/>`_.
-* 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.
+* Encoding the actual oops and preceding dmesg in a QR might help with the
+ dread "important stuff scrolled away" problem. See `[RFC][PATCH] Oops messages
+ transfer using QR codes
+ <https://lore.kernel.org/lkml/1446217392-11981-1-git-send-email-alexandru.murtaza@intel.com/>`_
+ for some example code that could be reused.
Contact: Daniel Vetter