Reviewed-by: Sagar Arun Kamble <sagar.a.kam...@intel.com>

On 9/23/2015 2:18 AM, yu....@intel.com wrote:
From: Alex Dai <yu....@intel.com>

Bit 16 of GuC status indicates resuming from RC6. The LAPIC_DONE
status is a reliable readiness flag only when resuming from RC6.
This fix a racing issue that allocation of doorbell fails whilst
GuC init is not finished.

Signed-off-by: Alex Dai <yu....@intel.com>
---
  drivers/gpu/drm/i915/i915_guc_reg.h     | 1 +
  drivers/gpu/drm/i915/intel_guc_loader.c | 5 +++--
  2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_guc_reg.h 
b/drivers/gpu/drm/i915/i915_guc_reg.h
index 8c8e574..dd0e1e8 100644
--- a/drivers/gpu/drm/i915/i915_guc_reg.h
+++ b/drivers/gpu/drm/i915/i915_guc_reg.h
@@ -37,6 +37,7 @@
  #define   GS_UKERNEL_READY              (0xF0 << GS_UKERNEL_SHIFT)
  #define   GS_MIA_SHIFT                        16
  #define   GS_MIA_MASK                   (0x07 << GS_MIA_SHIFT)
+#define   GS_MIA_CORE_STATE              (1 << GS_MIA_SHIFT)
#define SOFT_SCRATCH(n) (0xc180 + ((n) * 4)) diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
index e0601cc..40241f3 100644
--- a/drivers/gpu/drm/i915/intel_guc_loader.c
+++ b/drivers/gpu/drm/i915/intel_guc_loader.c
@@ -209,9 +209,10 @@ static inline bool guc_ucode_response(struct 
drm_i915_private *dev_priv,
                                      u32 *status)
  {
        u32 val = I915_READ(GUC_STATUS);
+       u32 uk_val = val & GS_UKERNEL_MASK;
        *status = val;
-       return ((val & GS_UKERNEL_MASK) == GS_UKERNEL_READY ||
-               (val & GS_UKERNEL_MASK) == GS_UKERNEL_LAPIC_DONE);
+       return (uk_val == GS_UKERNEL_READY ||
+               ((val & GS_MIA_CORE_STATE) && uk_val == GS_UKERNEL_LAPIC_DONE));
  }
/*

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