[Intel-gfx] [PATCH] drm/i915/gt: Make the CTX_TIMESTAMP readable on !rcs

[Chris Wilson]

For reasons that be, the HW only allows usersace to read its own
CTX_TIMESTAMP [context local HW runtime] on rcs. Make it available for
all by adding it to the whitelists.

v2: The change took effect from Cometlake.
v3: Ignore timestamps that autoincrement when validating the whitelist

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_workarounds.c   | 25 ++++++++++++++++++-
 .../gpu/drm/i915/gt/selftest_workarounds.c    | 17 +++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index 6e1accbcc045..0731bbcef06c 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -1206,6 +1206,18 @@ static void cfl_whitelist_build(struct intel_engine_cs *engine)
 			  RING_FORCE_TO_NONPRIV_RANGE_4);
 }
 
+static void cml_whitelist_build(struct intel_engine_cs *engine)
+{
+	struct i915_wa_list *w = &engine->whitelist;
+
+	if (engine->class != RENDER_CLASS)
+		whitelist_reg_ext(w,
+				  RING_CTX_TIMESTAMP(engine->mmio_base),
+				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
+
+	cfl_whitelist_build(engine);
+}
+
 static void cnl_whitelist_build(struct intel_engine_cs *engine)
 {
 	struct i915_wa_list *w = &engine->whitelist;
@@ -1256,9 +1268,15 @@ static void icl_whitelist_build(struct intel_engine_cs *engine)
 		/* hucStatus2RegOffset */
 		whitelist_reg_ext(w, _MMIO(0x23B0 + engine->mmio_base),
 				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
+		whitelist_reg_ext(w,
+				  RING_CTX_TIMESTAMP(engine->mmio_base),
+				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
 		break;
 
 	default:
+		whitelist_reg_ext(w,
+				  RING_CTX_TIMESTAMP(engine->mmio_base),
+				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
 		break;
 	}
 }
@@ -1290,6 +1308,9 @@ static void tgl_whitelist_build(struct intel_engine_cs *engine)
 		whitelist_reg(w, HIZ_CHICKEN);
 		break;
 	default:
+		whitelist_reg_ext(w,
+				  RING_CTX_TIMESTAMP(engine->mmio_base),
+				  RING_FORCE_TO_NONPRIV_ACCESS_RD);
 		break;
 	}
 }
@@ -1307,7 +1328,9 @@ void intel_engine_init_whitelist(struct intel_engine_cs *engine)
 		icl_whitelist_build(engine);
 	else if (IS_CANNONLAKE(i915))
 		cnl_whitelist_build(engine);
-	else if (IS_COFFEELAKE(i915) || IS_COMETLAKE(i915))
+	else if (IS_COMETLAKE(i915))
+		cml_whitelist_build(engine);
+	else if (IS_COFFEELAKE(i915))
 		cfl_whitelist_build(engine);
 	else if (IS_GEMINILAKE(i915))
 		glk_whitelist_build(engine);
diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
index 32785463ec9e..febc9e6692ba 100644
--- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
@@ -417,6 +417,20 @@ static bool wo_register(struct intel_engine_cs *engine, u32 reg)
 	return false;
 }
 
+static bool timestamp(const struct intel_engine_cs *engine, u32 reg)
+{
+	reg = (reg - engine->mmio_base) & ~RING_FORCE_TO_NONPRIV_ACCESS_MASK;
+	switch (reg) {
+	case 0x358:
+	case 0x35c:
+	case 0x3a8:
+		return true;
+
+	default:
+		return false;
+	}
+}
+
 static bool ro_register(u32 reg)
 {
 	if ((reg & RING_FORCE_TO_NONPRIV_ACCESS_MASK) ==
@@ -497,6 +511,9 @@ static int check_dirty_whitelist(struct intel_context *ce)
 		if (wo_register(engine, reg))
 			continue;
 
+		if (timestamp(engine, reg))
+			continue; /* timestamps are expected to autoincrement */
+
 		ro_reg = ro_register(reg);
 
 		/* Clear non priv flags */
-- 
2.20.1