On Tue, Aug 6, 2019 at 12:48 PM Brian Starkey brian.starkey@arm.com wrote:
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.
Signed-off-by: Brian Starkey brian.starkey@arm.com
lgtm, my earlier r-b holds. Well maybe should have a v2 here somewhere with what you changed. -Daniel
drivers/gpu/drm/drm_debugfs_crc.c | 17 +++++++++++++---- include/drm/drm_crtc.h | 4 ++++ 2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c index 7ca486d750e9..77159b6e77c3 100644 --- a/drivers/gpu/drm/drm_debugfs_crc.c +++ b/drivers/gpu/drm/drm_debugfs_crc.c @@ -65,10 +65,19 @@
- it submits. In this general case, the maximum userspace can do is to compare
- the reported CRCs of frames that should have the same contents.
- On the driver side the implementation effort is minimal, drivers only need to
- implement &drm_crtc_funcs.set_crc_source. The debugfs files are automatically
- set up if that vfunc is set. CRC samples need to be captured in the driver by
- calling drm_crtc_add_crc_entry().
- On the driver side the implementation effort is minimal, drivers only need
- to implement &drm_crtc_funcs.set_crc_source. The debugfs files are
- automatically set up if that vfunc is 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) diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index 128d8b210621..7d14c11bdc0a 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -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: *-- 2.17.1