[PATCH] drm/i915/psr: Preserve SRD_CTL bit 29 on PSR init

[Jim Bride <jim.bride@linux.intel.com>]

Bit 29 of SRD_CTL needs to have its value preserved, so right before we
write out the register we go ahead and read the register and preserve
the value of that bit before we write out the configured register value.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jim Bride <jim.bride@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h  | 1 +
 drivers/gpu/drm/i915/intel_psr.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b2546ad..ea8e421 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3872,6 +3872,7 @@ enum {
 #define EDP_PSR_CTL				_MMIO(dev_priv->psr_mmio_base + 0)
 #define   EDP_PSR_ENABLE			(1<<31)
 #define   BDW_PSR_SINGLE_FRAME			(1<<30)
+#define   EDP_PSR_RESTORE_PSR_ACTIVE_CTX        (1<<29) /* SW can't modify */
 #define   EDP_PSR_LINK_STANDBY			(1<<27)
 #define   EDP_PSR_MIN_LINK_ENTRY_TIME_MASK	(3<<25)
 #define   EDP_PSR_MIN_LINK_ENTRY_TIME_8_LINES	(0<<25)
diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index 559f1ab..0d08efa 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -315,6 +315,7 @@ static void intel_enable_source_psr1(struct intel_dp *intel_dp)
 	else
 		val |= EDP_PSR_TP1_TP2_SEL;
 
+	val |= I915_READ(EDP_PSR_CTL) & EDP_PSR_RESTORE_PSR_ACTIVE_CTX;
 	I915_WRITE(EDP_PSR_CTL, val);
 }
 
-- 
2.7.4

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