[PATCH v11 1/2] drm/i915: Implement WaProgramMgsrForCorrectSliceSpecificMmioReads

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

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:
 - Rebased.
v8:
 - Reviewed by Oscar
 - Store default MCR value instead of calculate on the run. (Oscar)
v9:
 - Changed naming and label fixes. (Oscar)
 - Store only the selector instead of whole MCR. (Oscar)
v10:
 - Improved comments, naming and line breaknig. (Oscar)
v11:
 - Moved the comment to most relavent block. (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/intel_device_info.c | 47 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_device_info.h |  3 ++
 drivers/gpu/drm/i915/intel_engine_cs.c   | 10 +++----
 3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_device_info.c b/drivers/gpu/drm/i915/intel_device_info.c
index a32ba72..ea62d45 100644
--- a/drivers/gpu/drm/i915/intel_device_info.c
+++ b/drivers/gpu/drm/i915/intel_device_info.c
@@ -719,6 +719,51 @@ static u32 read_timestamp_frequency(struct drm_i915_private *dev_priv)
 	return 0;
 }
 
+
+static void sanitize_mcr(struct intel_device_info *info)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(info, struct drm_i915_private, info);
+	u32 mcr;
+	u32 mcr_slice_subslice_mask;
+	u32 mcr_slice_subslice_select;
+	u32 slice = fls(info->sseu.slice_mask);
+	u32 subslice = fls(info->sseu.subslice_mask[slice]);
+
+	if (INTEL_GEN(dev_priv) >= 11) {
+		mcr_slice_subslice_mask = GEN11_MCR_SLICE_MASK |
+					  GEN11_MCR_SUBSLICE_MASK;
+		mcr_slice_subslice_select = GEN11_MCR_SLICE(slice) |
+						GEN11_MCR_SUBSLICE(subslice);
+	} else {
+		mcr_slice_subslice_mask = GEN8_MCR_SLICE_MASK |
+					  GEN8_MCR_SUBSLICE_MASK;
+		mcr_slice_subslice_select = GEN8_MCR_SLICE(slice) |
+						GEN8_MCR_SUBSLICE(subslice);
+	}
+
+	mcr = I915_READ(GEN8_MCR_SELECTOR);
+	mcr &= ~mcr_slice_subslice_mask;
+
+	/*
+	 * WaProgramMgsrForCorrectSliceSpecificMmioReads:cnl,icl
+	 * 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.
+	 */
+	if (INTEL_GEN(dev_priv) >= 10)
+		mcr |= mcr_slice_subslice_select;
+
+	I915_WRITE(GEN8_MCR_SELECTOR, mcr);
+
+	info->default_mcr_s_ss_select = mcr_slice_subslice_select;
+}
+
 /**
  * intel_device_info_runtime_init - initialize runtime info
  * @info: intel device info struct
@@ -851,6 +896,8 @@ void intel_device_info_runtime_init(struct intel_device_info *info)
 	else if (INTEL_INFO(dev_priv)->gen >= 11)
 		gen11_sseu_info_init(dev_priv);
 
+	sanitize_mcr(info);
+
 	/* Initialize command stream timestamp frequency */
 	info->cs_timestamp_frequency_khz = read_timestamp_frequency(dev_priv);
 }
diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
index 933e316..2feccee 100644
--- a/drivers/gpu/drm/i915/intel_device_info.h
+++ b/drivers/gpu/drm/i915/intel_device_info.h
@@ -176,6 +176,9 @@ struct intel_device_info {
 	/* Slice/subslice/EU info */
 	struct sseu_dev_info sseu;
 
+	/* default selected slice/subslice in MCR packet control */
+	u32 default_mcr_s_ss_select;
+
 	u32 cs_timestamp_frequency_khz;
 
 	struct color_luts {
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 1a83707..2b24277 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -831,11 +831,9 @@ 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.
-	 */
-	WARN_ON_ONCE(mcr & mcr_slice_subslice_mask);
+
+	WARN_ON_ONCE((mcr & mcr_slice_subslice_mask) !=
+		      dev_priv->info.default_mcr_s_ss_select);
 	mcr &= ~mcr_slice_subslice_mask;
 	mcr |= mcr_slice_subslice_select;
 	I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr);
@@ -843,6 +841,8 @@ read_subslice_reg(struct drm_i915_private *dev_priv, int slice,
 	ret = I915_READ_FW(reg);
 
 	mcr &= ~mcr_slice_subslice_mask;
+	mcr |= dev_priv->info.default_mcr_s_ss_select;
+
 	I915_WRITE_FW(GEN8_MCR_SELECTOR, mcr);
 
 	intel_uncore_forcewake_put__locked(dev_priv, fw_domains);
-- 
2.7.4

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