From 4db3189ce0621be901f249f8cd8226c977dd601d Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 24 Feb 2022 14:24:25 +0100 Subject: drm/todo: Update panic handling todo Some things changed, and add two useful links. v2: Also include a link to the QR encoding work. Plus review from Javier. v3: Fix typo Guilherme spotted. Reviewed-by: Guilherme G. Piccoli Acked-by: Pekka Paalanen Reviewed-by: Javier Martinez Canillas Cc: Javier Martinez Canillas Cc: Pekka Paalanen Cc: gpiccoli@igalia.com Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220224132425.3463791-1-daniel.vetter@ffwll.ch --- Documentation/gpu/todo.rst | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) (limited to 'Documentation/gpu/todo.rst') diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 1b2372ef4131..d6a7ebf717be 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -499,8 +499,12 @@ 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 + `_. * ``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 @@ -512,16 +516,15 @@ 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 + `_. -* 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 + `_ + for some example code that could be reused. Contact: Daniel Vetter -- cgit From 9ae2ac4d31a85ce59cc560d514a31b95f4ace154 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 23 Feb 2022 20:38:04 +0100 Subject: drm: Add TODO item for optimizing format helpers Add a TODO item for optimizing blitting and format-conversion helpers in DRM and fbdev. There's always demand for faster graphics output. v4: * fix typos (Sam) Signed-off-by: Thomas Zimmermann Reviewed-by: Javier Martinez Canillas Acked-by: Sam Ravnborg Link: https://patchwork.freedesktop.org/patch/msgid/20220223193804.18636-6-tzimmermann@suse.de --- Documentation/gpu/todo.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'Documentation/gpu/todo.rst') diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index d6a7ebf717be..4260c62d751b 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -241,6 +241,28 @@ Contact: Thomas Zimmermann , 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 + +Level: Intermediate drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup ----------------------------------------------------------------- -- cgit