[Intel-gfx] [PATCH 4/7] drm/i915: PSR: Mask LPSP hw tracking back again.

[Rodrigo Vivi]

At the beginning it was masked to allow PSR at all.
Than it got removed later by my
commit 09108b90f040 ("drm/i915: PSR: Remove Low Power HW tracking mask.")
in order to trying fixing one case reported at intel-gfx mailing list
where we were missing screen updates when runtime_pm was enabled.

However I verified that other patch that makes flush to force
invalidate also fixes this issue by itself.
commit 169de1316c1e ("drm/i915: PSR: Flush means invalidate + flush")

Mainly now that we are relying more on frontbuffer tracking it is a
good idea to mask this hw tracking again.

But besides all this above it is important to hightligh that with LPSP
unmasked we started seeing some screen freezings as reported at fd.o.

This patch fixes the unrecoverable frozen screens reported:

Reference: https://bugs.freedesktop.org/show_bug.cgi?id=91436
Reference: https://bugs.freedesktop.org/show_bug.cgi?id=91437

Cc: Ivan Mitev <ivan.mitev at gmail.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/intel_psr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index 63bbab2..d02d4e2 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -398,9 +398,14 @@ void intel_psr_enable(struct intel_dp *intel_dp)
 				skl_psr_setup_su_vsc(intel_dp);
 		}
 
-		/* Avoid continuous PSR exit by masking memup and hpd */
+		/*
+		 * Per Spec: Avoid continuous PSR exit by masking MEMUP and HPD.
+		 * Also mask LPSP to avoid dependency on other drivers that
+		 * might block runtime_pm besides preventing other hw tracking
+		 * issues now we can rely on frontbuffer tracking.
+		 */
 		I915_WRITE(EDP_PSR_DEBUG_CTL(dev), EDP_PSR_DEBUG_MASK_MEMUP |
-			   EDP_PSR_DEBUG_MASK_HPD);
+			   EDP_PSR_DEBUG_MASK_HPD | EDP_PSR_DEBUG_MASK_LPSP);
 
 		/* Enable PSR on the panel */
 		hsw_psr_enable_sink(intel_dp);
-- 
2.4.3