[Intel-gfx] [PATCH v6 1/2] drm/i915/cnl: Implement WaProgramMgsrForCorrectSliceSpecificMmioReads

[Yunwei Zhang]

WaProgramMgsrForCorrectSliceSpecificMmioReads dictate that before any MMIO
read into Slice/Subslice specific registers, MCR packet control
register(0xFDC) needs to be programmed to point to any enabled
slice/subslice pair. Otherwise, incorrect value will be returned.

However, that means each subsequent MMIO read will be forwarded to a
specific slice/subslice combination as read is unicast. This is OK since
slice/subslice specific register values are consistent in almost all cases
across slice/subslice. There are rare occasions such as INSTDONE that this
value will be dependent on slice/subslice combo, in such cases, we need to
program 0xFDC and recover this after. This is already covered by
read_subslice_reg.

Also, 0xFDC will lose its information after TDR/engine reset/power state
change.

References: HSD#1405586840, BSID#0575

v2:
 - use fls() instead of find_last_bit() (Chris)
 - added INTEL_SSEU to extract sseu from device info. (Chris)
v3:
 - rebase on latest tip
v5:
 - Added references (Mika)
 - Change the ordered of passing arguments and etc. (Ursulin)
v6:
 - Updated the comment that conflict with the patch. (Chris)

Cc: Oscar Mateo <oscar.mateo at intel.com>
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Signed-off-by: Yunwei Zhang <yunwei.zhang at intel.com>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 42 +++++++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 12486d8..4c50bee 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -796,6 +796,27 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type)
 	}
 }
 
+static u32 calculate_mcr(struct drm_i915_private *dev_priv, u32 mcr)
+{
+	const struct sseu_dev_info *sseu = &(INTEL_INFO(dev_priv)->sseu);
+	u32 slice = fls(sseu->slice_mask);
+	u32 subslice = fls(sseu->subslice_mask[slice]);
+
+	mcr &= ~(GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK);
+	mcr |= GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice);
+
+	return mcr;
+}
+
+static void wa_init_mcr(struct drm_i915_private *dev_priv)
+{
+	u32 mcr;
+
+	mcr = I915_READ(GEN8_MCR_SELECTOR);
+	mcr = calculate_mcr(dev_priv, mcr);
+	I915_WRITE(GEN8_MCR_SELECTOR, mcr);
+}
+
 static inline uint32_t
 read_subslice_reg(struct drm_i915_private *dev_priv, int slice,
 		  int subslice, i915_reg_t reg)
@@ -828,18 +849,30 @@ read_subslice_reg(struct drm_i915_private *dev_priv, int slice,
 	intel_uncore_forcewake_get__locked(dev_priv, fw_domains);
 
 	mcr = I915_READ_FW(GEN8_MCR_SELECTOR);
+
 	/*
 	 * The HW expects the slice and sublice selectors to be reset to 0
-	 * after reading out the registers.
+	 * before GEN10 or to a enabled s/ss post GEN10 after reading out the
+	 * registers.
 	 */
-	WARN_ON_ONCE(mcr & mcr_slice_subslice_mask);
+	WARN_ON_ONCE(INTEL_GEN(dev_priv) < 10 &&
+		     (mcr & mcr_slice_subslice_mask));
 	mcr &= ~mcr_slice_subslice_mask;
 	mcr |= mcr_slice_subslice_select;
 	I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr);
 
 	ret = I915_READ_FW(reg);
 
-	mcr &= ~mcr_slice_subslice_mask;
+	/*
+	 * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl
+	 * expects mcr to be programed to a enabled slice/subslice pair
+	 * before any MMIO read into slice/subslice register
+	 */
+	if (INTEL_GEN(dev_priv) < 10)
+		mcr &= ~mcr_slice_subslice_mask;
+	else
+		mcr = calculate_mcr(dev_priv, mcr);
+
 	I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr);
 
 	intel_uncore_forcewake_put__locked(dev_priv, fw_domains);
@@ -1307,6 +1340,9 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine)
 	struct drm_i915_private *dev_priv = engine->i915;
 	int ret;
 
+	/* WaProgramMgsrForCorrectSliceSpecificMmioReads: cnl */
+	wa_init_mcr(dev_priv);
+
 	/* WaDisableI2mCycleOnWRPort:cnl (pre-prod) */
 	if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0))
 		I915_WRITE(GAMT_CHKN_BIT_REG,
-- 
2.7.4