drm/i915: Whitelist SLICE_COMMON_ECO_CHICKEN1 on Geminilake.

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@whitecape.org>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180105085905.9298-1-kenneth@whitecape.org
(cherry picked from commit ab062639edb0412daf6de540725276b9a5d217f9)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 333f40b..7923dfd 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7027,6 +7027,8 @@ 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 ab5bf4e..6074e04 100644 (file)
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1390,6 +1390,11 @@ 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);