drm/i915/gen9: implement WaConextSwitchWithConcurrentTLBInvalidate

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.

v2: move to gen9_init_workarounds (Arun)
v3: move to start of gen9_init_workarounds (Arun)

Signed-off-by: Tim Gore <tim.gore@intel.com>
Reviewed-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465816501-25557-1-git-send-email-tim.gore@intel.com
(cherry picked from commit a8ab5ed5e1bf856eceaab5579236de6f92822b9f)
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b2fbbfa..3fcf7dd 100644 (file)
--- 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)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 279614c..68c5af0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -915,6 +915,9 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;
 
+       /* WaConextSwitchWithConcurrentTLBInvalidate:skl,bxt,kbl */
+       I915_WRITE(GEN9_CSFE_CHICKEN1_RCS, _MASKED_BIT_ENABLE(GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE));
+
        /* WaEnableLbsSlaRetryTimerDecrement:skl,bxt,kbl */
        I915_WRITE(BDW_SCRATCH1, I915_READ(BDW_SCRATCH1) |
                   GEN9_LBS_SLA_RETRY_TIMER_DECREMENT_ENABLE);