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drm/crc-debugfs: Add notes about CRC<->commit interactions

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CRC generation can be impacted by commits coming from userspace, and
enabling CRC generation may itself trigger a commit. Add notes about
this to the kerneldoc.

Changes since v1:
 - Clarified that anything that would disable CRCs counts as a full
   modeset, and so userspace needs to reconfigure after full modesets

Changes since v2:
 - Add these notes
 - Rebase onto drm-misc-next (trivial conflict in comment)

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Ayan Kumar Halder <ayan.halder@arm.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Link:- https://patchwork.freedesktop.org/patch/321974/
This commit is contained in:
Brian Starkey 2019-08-06 13:46:22 +01:00 committed by Ayan kumar halder
parent bc0380b9e5
commit 178e5f3a5b
2 changed files with 13 additions and 0 deletions
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9
drivers/gpu/drm/drm_debugfs_crc.c
View File

@ -69,6 +69,15 @@
* implement &drm_crtc_funcs.set_crc_source and &drm_crtc_funcs.verify_crc_source.
* The debugfs files are automatically set up if those vfuncs are set. CRC samples
* need to be captured in the driver by calling drm_crtc_add_crc_entry().
* Depending on the driver and HW requirements, &drm_crtc_funcs.set_crc_source
* may result in a commit (even a full modeset).
*
* CRC results must be reliable across non-full-modeset atomic commits, so if a
* commit via DRM_IOCTL_MODE_ATOMIC would disable or otherwise interfere with
* CRC generation, then the driver must mark that commit as a full modeset
* (drm_atomic_crtc_needs_modeset() should return true). As a result, to ensure
* consistent results, generic userspace must re-setup CRC generation after a
* legacy SETCRTC or an atomic commit with DRM_MODE_ATOMIC_ALLOW_MODESET.
*/
static int crc_control_show(struct seq_file *m, void *data)

4
include/drm/drm_crtc.h
View File

@ -756,6 +756,9 @@ struct drm_crtc_funcs {
* provided from the configured source. Drivers must accept an "auto"
* source name that will select a default source for this CRTC.
*
* This may trigger an atomic modeset commit if necessary, to enable CRC
* generation.
*
* Note that "auto" can depend upon the current modeset configuration,
* e.g. it could pick an encoder or output specific CRC sampling point.
*
@ -767,6 +770,7 @@ struct drm_crtc_funcs {
* 0 on success or a negative error code on failure.
*/
int (*set_crc_source)(struct drm_crtc *crtc, const char *source);
/**
* @verify_crc_source:
*