[Intel-gfx] [PATCH] drm/i915/psr: Send update also on invalidate

["Jouni Högander" <jouni.hogander@intel.com>]

Currently we are observing mouse cursor stuttering when using
xrandr --scaling=1.2x1.2. X scaling/transformation seems to be
doing fronbuffer rendering. When moving mouse cursor X seems to
perform several invalidates and only one DirtyFB. I.e. it seems
to be assuming updates are sent to panel while drawing is done.

Earlier we were disabling PSR in frontbuffer invalidate call back
(when drawing in X started). PSR was re-enabled in frontbuffer
flush callback (dirtyfb ioctl). This was working fine with X
scaling/transformation. Now we are just enabling continuous full
frame (cff) in PSR invalidate callback. Enabling cff doesn't
trigger any updates. It just configures PSR to send full frame
when updates are sent. I.e. there are no updates on screen before
PSR flush callback is made. X seems to be doing several updates
in frontbuffer before doing dirtyfb ioctl.

Fix this by sending single update on every invalidate callback.

Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>

Fixes: 805f04d42a6b ("drm/i915/display/psr: Use continuos full frame to handle frontbuffer invalidations")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6679
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reported-by: Brian J. Tarricone <brian@tarricone.org>
Tested-by: Brian J. Tarricone <brian@tarricone.org>
---
 drivers/gpu/drm/i915/display/intel_psr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index 904a1049eff3..564d4fd94048 100644
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -2209,8 +2209,11 @@ static void _psr_invalidate_handle(struct intel_dp *intel_dp)
 	if (intel_dp->psr.psr2_sel_fetch_enabled) {
 		u32 val;
 
-		if (intel_dp->psr.psr2_sel_fetch_cff_enabled)
+		if (intel_dp->psr.psr2_sel_fetch_cff_enabled) {
+			/* Send one update otherwise lag is observed in screen */
+			intel_de_write(dev_priv, CURSURFLIVE(intel_dp->psr.pipe), 0);
 			return;
+		}
 
 		val = man_trk_ctl_enable_bit_get(dev_priv) |
 		      man_trk_ctl_partial_frame_bit_get(dev_priv) |
-- 
2.34.1