On 09/06/2016 13:48, [email protected] wrote:
From: Tim Gore <[email protected]>

This patch enables a workaround for a mid thread preemption
issue where a hardware timing problem can prevent the
context restore from happening, leading to a hang.

Signed-off-by: Tim Gore <[email protected]>
---
  drivers/gpu/drm/i915/i915_gem_gtt.c | 6 ++++++
  drivers/gpu/drm/i915/i915_reg.h     | 4 ++++
  2 files changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c 
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 4668477..e9046f6 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2156,6 +2156,12 @@ static void gtt_write_workarounds(struct drm_device *dev)
                I915_WRITE(GEN8_L3_LRA_1_GPGPU, 
GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_SKL);
        else if (IS_BROXTON(dev))
                I915_WRITE(GEN8_L3_LRA_1_GPGPU, 
GEN9_L3_LRA_1_GPGPU_DEFAULT_VALUE_BXT);
+
+       /* WaConextSwitchWithConcurrentTLBInvalidate:gen9 */
+       if (IS_GEN9(dev))
+       {
+               I915_WRITE(GEN9_CSFE_CHICKEN1_RCS, 
_MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));
+       }
This is not the correct place, it should be added in gen9_init_workarounds() in intel_ringbuffer.c as it applies to both skl and bxt.

Please also correct the spelling and we usually mention both skl, bxt instead of gen9.
WaContextSwitchWithConcurrentTLBInvalidate:skl,bxt

regards
Arun

  }

  static int i915_ppgtt_init(struct drm_device *dev, struct i915_hw_ppgtt 
*ppgtt)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 81d1896..2a6fc62 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1810,6 +1810,10 @@ enum skl_disp_power_wells {
  #define   GEN9_IZ_HASHING_MASK(slice)                 (0x3 << ((slice) * 2))
  #define   GEN9_IZ_HASHING(slice, val)                 ((val) << ((slice) * 2))

+/* chicken reg for WaConextSwitchWithConcurrentTLBInvalidate */
+#define GEN9_CSFE_CHICKEN1_RCS _MMIO(0x20D4)
+#define   GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE (1 << 2)
+
  /* WaClearTdlStateAckDirtyBits */
  #define GEN8_STATE_ACK                _MMIO(0x20F0)
  #define GEN9_STATE_ACK_SLICE1 _MMIO(0x20F8)


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