drm/i915/cnl: Implement WaProgramMgsrForCorrectSliceSpecificMmioReads

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)
v7:
 - Moved WA explanation Comments(Oscar)
 - Rebased.
v8:
 - Renamed sanitize_mcr to calculate_s_ss_select. (Oscar)
 - calculate s/ss selector instead of whole mcr. (Oscar)
v9:
 - Updated function name (Oscar)
 - Remove redundant variables (Oscar)
v10:
 - Separate pre-GEN10 and GEN11 mask. (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>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1526683197-24656-1-git-send-email-yunwei.zhang@intel.com

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
index 2df3538ceba5..720d8635c2cf 100644
--- a/drivers/gpu/drm/i915/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/intel_workarounds.c
@@ -672,8 +672,35 @@ static void cfl_gt_workarounds_apply(struct drm_i915_private *dev_priv)
 		   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
 }
 
+static void wa_init_mcr(struct drm_i915_private *dev_priv)
+{
+	u32 mcr;
+	u32 mcr_slice_subslice_mask;
+
+	mcr = I915_READ(GEN8_MCR_SELECTOR);
+
+	mcr_slice_subslice_mask = GEN8_MCR_SLICE_MASK |
+				  GEN8_MCR_SUBSLICE_MASK;
+	/*
+	 * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl
+	 * Before any MMIO read into slice/subslice specific registers, MCR
+	 * packet control register needs to be programmed to point to any
+	 * enabled s/ss pair. Otherwise, incorrect values will be returned.
+	 * This means each subsequent MMIO read will be forwarded to an
+	 * specific s/ss combination, but this is OK since these registers
+	 * are consistent across s/ss in almost all cases. In the rare
+	 * occasions, such as INSTDONE, where this value is dependent
+	 * on s/ss combo, the read should be done with read_subslice_reg.
+	 */
+	mcr &= ~mcr_slice_subslice_mask;
+	mcr |= intel_calculate_mcr_s_ss_select(dev_priv);
+	I915_WRITE(GEN8_MCR_SELECTOR, mcr);
+}
+
 static void cnl_gt_workarounds_apply(struct drm_i915_private *dev_priv)
 {
+	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,