From 178e5f3a5bc1d67d1248a74c0abab41040abe7c4 Mon Sep 17 00:00:00 2001 From: Brian Starkey Date: Tue, 6 Aug 2019 13:46:22 +0100 Subject: drm/crc-debugfs: Add notes about CRC<->commit interactions 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 Signed-off-by: Ayan Kumar Halder Reviewed-by: Daniel Vetter Link:- https://patchwork.freedesktop.org/patch/321974/ --- drivers/gpu/drm/drm_debugfs_crc.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/gpu/drm/drm_debugfs_crc.c') 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) -- cgit