| Message ID | 20190806124622.28399-1-brian.starkey@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] drm/crc-debugfs: Add notes about CRC<->commit interactions | expand |
On Tue, Aug 06, 2019 at 01:46:22PM +0100, Brian Starkey 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. > > 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> > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > --- > drivers/gpu/drm/drm_debugfs_crc.c | 9 +++++++++ > include/drm/drm_crtc.h | 4 ++++ > 2 files changed, 13 insertions(+) > > diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c > index 6604ed223160..be1b7ba92ffe 100644 > --- a/drivers/gpu/drm/drm_debugfs_crc.c > +++ b/drivers/gpu/drm/drm_debugfs_crc.c > @@ -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) > 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 > Pushed to drm-misc-next. Commit id :- 178e5f3a5bc1d67d1248a74c0abab41040abe7c4 -Ayan > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c index 6604ed223160..be1b7ba92ffe 100644 --- a/drivers/gpu/drm/drm_debugfs_crc.c +++ b/drivers/gpu/drm/drm_debugfs_crc.c @@ -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) 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: *