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@xxxxxxx>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> 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
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