[PATCH v8 2/2] drm/i915: Implement WaProgramMgsrForL3BankSpecificMmioReads

[Yunwei Zhang <yunwei.zhang@intel.com>]

L3Bank could be fused off in hardware for debug purpose, and it
is possible that subslice is enabled while its corresponding L3Bank pairs
are disabled. In such case, if MCR packet control register(0xFDC) is
programed to point to a disabled bank pair, a MMIO read into L3Bank range
will return 0 instead of correct values.

However, this is not going to be the case in any production silicon.
Therefore, we only check at initialization and issue a warning should
this really happen.

References: HSDES#1405586840

v2:
 - use fls instead of find_last_bit (Chris)
 - use is_power_of_2() instead of counting bit set (Chris)
v3:
 - rebase on latest tip
v5:
 - Added references (Mika)
 - Move local variable into scope where they are used (Ursulin)
 - use a new local variable to reduce long line of code (Ursulin)
v6:
 - Some coding style and use more local variables for clearer
   logic (Ursulin)
v7:
 - Rebased.
v8:
 - Reviewed by Oscar.

Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Yunwei Zhang <yunwei.zhang@intel.com>
Reviewed-by: Oscar Mateo <oscar.mateo@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h          |  4 ++++
 drivers/gpu/drm/i915/intel_device_info.c | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index fb10602..6c9c01b 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2709,6 +2709,10 @@ enum i915_power_well_id {
 #define   GEN10_F2_SS_DIS_SHIFT		18
 #define   GEN10_F2_SS_DIS_MASK		(0xf << GEN10_F2_SS_DIS_SHIFT)
 
+#define	GEN10_MIRROR_FUSE3		_MMIO(0x9118)
+#define GEN10_L3BANK_PAIR_COUNT     4
+#define GEN10_L3BANK_MASK   0x0F
+
 #define GEN8_EU_DISABLE0		_MMIO(0x9134)
 #define   GEN8_EU_DIS0_S0_MASK		0xffffff
 #define   GEN8_EU_DIS0_S1_SHIFT		24
diff --git a/drivers/gpu/drm/i915/intel_device_info.c b/drivers/gpu/drm/i915/intel_device_info.c
index 2243a23..5a013fa 100644
--- a/drivers/gpu/drm/i915/intel_device_info.c
+++ b/drivers/gpu/drm/i915/intel_device_info.c
@@ -729,6 +729,29 @@ static void wa_init_mcr(struct intel_device_info *info)
 	u32 slice = fls(info->sseu.slice_mask);
 	u32 subslice = fls(info->sseu.subslice_mask[slice]);
 
+	/*
+	 * L3Banks could be fused off in single slice scenario, however, if
+	 * more than one slice is enabled, this should not happen.
+	 */
+	if (is_power_of_2(info->sseu.slice_mask)) {
+		/*
+		 * WaProgramMgsrForL3BankSpecificMmioReads:
+		 * read FUSE3 for enabled L3 Bank IDs, if L3 Bank matches
+		 * enabled subslice, no need to redirect MCR packet
+		 */
+		u32 fuse3 = I915_READ(GEN10_MIRROR_FUSE3);
+		u8 ss_mask = info->sseu.subslice_mask[slice];
+
+		u8 enabled_mask = (ss_mask | ss_mask >> 4) & 0xf;
+		u8 disabled_mask = fuse3 & 0xf;
+
+		/*
+		 * Production silicon should have matched L3Bank and
+		 * subslice enabled
+		 */
+		WARN_ON((enabled_mask & disabled_mask) != enabled_mask);
+	}
+
 	if (INTEL_GEN(dev_priv) >= 11) {
 		mcr_slice_subslice_mask = GEN11_MCR_SLICE_MASK |
 					  GEN11_MCR_SUBSLICE_MASK;
-- 
2.7.4

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