[Intel-gfx] [PATCH] drm/i915/gt: Skip rmw for masked registers

[Chris Wilson]

A masked register does not need rmw to update, and it is best not to use
such a sequence.

Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_workarounds.c | 32 ++++++++++++++-------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index 5a7db279f702..e4c2b6d42f46 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -116,7 +116,8 @@ static void _wa_add(struct i915_wa_list *wal, const struct i915_wa *wa)
 		} else {
 			wa_ = &wal->list[mid];
 
-			if ((wa->mask & ~wa_->mask) == 0) {
+			if ((wa->mask | wa_->mask) &&
+			    (wa->mask & ~wa_->mask) == 0) {
 				DRM_ERROR("Discarding overwritten w/a for reg %04x (mask: %08x, value: %08x)\n",
 					  i915_mmio_reg_offset(wa_->reg),
 					  wa_->mask, wa_->val);
@@ -167,12 +168,6 @@ wa_write_masked_or(struct i915_wa_list *wal, i915_reg_t reg, u32 mask,
 	wa_add(wal, reg, mask, val, mask);
 }
 
-static void
-wa_masked_en(struct i915_wa_list *wal, i915_reg_t reg, u32 val)
-{
-	wa_write_masked_or(wal, reg, val, _MASKED_BIT_ENABLE(val));
-}
-
 static void
 wa_write(struct i915_wa_list *wal, i915_reg_t reg, u32 val)
 {
@@ -185,14 +180,26 @@ wa_write_or(struct i915_wa_list *wal, i915_reg_t reg, u32 val)
 	wa_write_masked_or(wal, reg, val, val);
 }
 
+static void
+wa_masked_en(struct i915_wa_list *wal, i915_reg_t reg, u32 val)
+{
+	wa_add(wal, reg, 0, _MASKED_BIT_ENABLE(val), val);
+}
+
+static void
+wa_masked_dis(struct i915_wa_list *wal, i915_reg_t reg, u32 val)
+{
+	wa_add(wal, reg, 0, _MASKED_BIT_DISABLE(val), val);
+}
+
 #define WA_SET_BIT_MASKED(addr, mask) \
-	wa_write_masked_or(wal, (addr), (mask), _MASKED_BIT_ENABLE(mask))
+	wa_masked_en(wal, (addr), mask)
 
 #define WA_CLR_BIT_MASKED(addr, mask) \
-	wa_write_masked_or(wal, (addr), (mask), _MASKED_BIT_DISABLE(mask))
+	wa_masked_dis(wal, (addr), mask)
 
 #define WA_SET_FIELD_MASKED(addr, mask, value) \
-	wa_write_masked_or(wal, (addr), (mask), _MASKED_FIELD((mask), (value)))
+	wa_write_masked_or(wal, (addr), 0, _MASKED_FIELD((mask), (value)))
 
 static void gen8_ctx_workarounds_init(struct intel_engine_cs *engine,
 				      struct i915_wa_list *wal)
@@ -1020,7 +1027,10 @@ wa_list_apply(struct intel_uncore *uncore, const struct i915_wa_list *wal)
 	intel_uncore_forcewake_get__locked(uncore, fw);
 
 	for (i = 0, wa = wal->list; i < wal->count; i++, wa++) {
-		intel_uncore_rmw_fw(uncore, wa->reg, wa->mask, wa->val);
+		if (wa->mask)
+			intel_uncore_rmw_fw(uncore, wa->reg, wa->mask, wa->val);
+		else
+			intel_uncore_write_fw(uncore, wa->reg, wa->val);
 		if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
 			wa_verify(wa,
 				  intel_uncore_read_fw(uncore, wa->reg),
-- 
2.25.0