lkml.org 
[lkml]   [2024]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFT PATCH v2 48/48] drm/panel: Update TODO list item for cleaning up prepared/enabled tracking
Date
Now that most panels have been updated not to track/double-check their
prepared/enabled state update the TODO with next steps.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

(no changes since v1)

Documentation/gpu/todo.rst | 47 +++++++++++++++++++++-----------------
1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index e2a0585915b3..4063bc45bbd3 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -469,30 +469,35 @@ Contact: Thomas Zimmermann <tzimmermann@suse.de>

Level: Starter

-Clean up checks for already prepared/enabled in panels
-------------------------------------------------------
-
-In a whole pile of panel drivers, we have code to make the
-prepare/unprepare/enable/disable callbacks behave as no-ops if they've already
-been called. To get some idea of the duplicated code, try::
-
- git grep 'if.*>prepared' -- drivers/gpu/drm/panel
- git grep 'if.*>enabled' -- drivers/gpu/drm/panel
-
-In the patch ("drm/panel: Check for already prepared/enabled in drm_panel")
-we've moved this check to the core. Now we can most definitely remove the
-check from the individual panels and save a pile of code.
-
-In adition to removing the check from the individual panels, it is believed
-that even the core shouldn't need this check and that should be considered
-an error if other code ever relies on this check. The check in the core
-currently prints a warning whenever something is relying on this check with
-dev_warn(). After a little while, we likely want to promote this to a
-WARN(1) to help encourage folks not to rely on this behavior.
+Remove disable/unprepare in remove/shutdown in panel-simple and panel-edp
+-------------------------------------------------------------------------
+
+As of commit d2aacaf07395 ("drm/panel: Check for already prepared/enabled in
+drm_panel"), we have a check in the drm_panel core to make sure nobody
+double-calls prepare/enable/disable/unprepare. Eventually that should probably
+be turned into a WARN_ON() or somehow made louder, but right now we actually
+expect it to trigger and so we don't want it to be too loud.
+
+Specifically, that warning will trigger for panel-edp and panel-simple at
+shutdown time because those panels hardcode a call to drm_panel_disable()
+and drm_panel_unprepare() at shutdown and remove time that they call regardless
+of panel state. On systems with a properly coded DRM modeset driver that
+calls drm_atomic_helper_shutdown() this is pretty much guaranteed to cause
+the warning to fire.
+
+Unfortunately we can't safely remove the calls in panel-edp and panel-simple
+until we're sure that all DRM modeset drivers that are used with those panels
+properly call drm_atomic_helper_shutdown(). This TODO item is to validate
+that all DRM modeset drivers used with panel-edp and panel-simple properly
+call drm_atomic_helper_shutdown() and then remove the calls to
+disable/unprepare from those panels. Alternatively, this TODO item could be
+removed by convincing stakeholders that those calls are fine and downgrading
+the error message in drm_panel_disable() / drm_panel_unprepare() to a
+debug-level message.

Contact: Douglas Anderson <dianders@chromium.org>

-Level: Starter/Intermediate
+Level: Intermediate


Core refactorings
--
2.45.0.rc1.225.g2a3ae87e7f-goog

\
 
 \ /
  Last update: 2024-05-27 18:15    [W:0.326 / U:0.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site