Geminilake requires the 3D driver to select whether barriers are
intended for compute shaders, or tessellation control shaders, by
whacking a "Barrier Mode" bit in SLICE_COMMON_ECO_CHICKEN1 when
switching pipelines. Failure to do this properly can result in GPU
hangs.
Unfortunately, this means it needs to switch mid-batch, so only
userspace can properly set it. To facilitate this, the kernel needs
to whitelist the register.
The workarounds page currently tags this as applying to Broxton only,
but that doesn't make sense. The documentation for the register it
references says the bit userspace is supposed to toggle only exists on
Geminilake. Empirically, the Mesa patch to toggle this bit appears to
fix intermittent GPU hangs in tessellation control shader barrier tests
on Geminilake; we haven't seen those hangs on Broxton.
v2: Mention WA #0862 in the comment (it doesn't have a name).
Signed-off-by: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
Acked-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/i915/i915_reg.h | 2 ++
drivers/gpu/drm/i915/intel_engine_cs.c | 5 +++++
2 files changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 966e4df9700e..505c605eff98 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7079,6 +7079,8 @@ enum {
#define GEN9_SLICE_COMMON_ECO_CHICKEN0 _MMIO(0x7308)
#define DISABLE_PIXEL_MASK_CAMMING (1<<14)
+#define GEN9_SLICE_COMMON_ECO_CHICKEN1 _MMIO(0x731c)
+
#define GEN7_L3SQCREG1 _MMIO(0xB010)
#define VLV_B0_WA_L3SQCREG1_VALUE 0x00D30000
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index ebdcbcbacb3c..6bb51a502b8b 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1338,6 +1338,11 @@ static int glk_init_workarounds(struct intel_engine_cs *engine)
if (ret)
return ret;
+ /* WA #0862: Userspace has to set "Barrier Mode" to avoid hangs. */
+ ret = wa_ring_whitelist_reg(engine, GEN9_SLICE_COMMON_ECO_CHICKEN1);
+ if (ret)
+ return ret;
+
/* WaToEnableHwFixForPushConstHWBug:glk */
WA_SET_BIT_MASKED(COMMON_SLICE_CHICKEN2,
GEN8_SBE_DISABLE_REPLAY_BUF_OPTIMIZATION);
--
2.15.1