[PATCH v3 15/29] drm/i915/dram: Add field ecc_impacting_de_bw

[Gustavo Sousa <gustavo.sousa@intel.com>]

Starting with Xe3p_LPD, we now have a new field in MEM_SS_INFO_GLOBAL
that indicates whether the memory has enabled ECC that limits display
bandwidth.  Add the field ecc_impacting_de_bw to struct dram_info to
contain that information and set it appropriately when probing for
memory info.

Currently there are no instructions in Bspec on how to handle that case,
so let's throw a warning if we ever find such a scenario.

v2:
  - s/ecc_impacting_de/ecc_impacting_de_bw/ to be more specific. (Matt
    Atwood)
  - Add warning if ecc_impacting_de_bw is true, since we currently do
    not have instructions on how to handle it. (Matt Roper)
v3:
  - Check on ecc_impacting_de_bw for the warning only for Xe3p_LPD and
    beyond.
  - Change warning macro from drm_WARN_ON_ONCE() to drm_WARN_ON().

Bspec: 69131
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
---
 drivers/gpu/drm/i915/display/intel_bw.c | 9 +++++++++
 drivers/gpu/drm/i915/i915_reg.h         | 1 +
 drivers/gpu/drm/i915/soc/intel_dram.c   | 4 ++++
 drivers/gpu/drm/i915/soc/intel_dram.h   | 1 +
 4 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
index 919b25a5fbac..1f6461be50ef 100644
--- a/drivers/gpu/drm/i915/display/intel_bw.c
+++ b/drivers/gpu/drm/i915/display/intel_bw.c
@@ -805,6 +805,15 @@ void intel_bw_init_hw(struct intel_display *display)
 	if (!HAS_DISPLAY(display))
 		return;
 
+	/*
+	 * Starting with Xe3p_LPD, the hardware tells us whether memory has ECC
+	 * enabled that would impact display bandwidth.  However, so far there
+	 * are no instructions in Bspec on how to handle that case.  Let's
+	 * complain if we ever find such a scenario.
+	 */
+	if (DISPLAY_VER(display) >= 35)
+		drm_WARN_ON(display->drm, dram_info->ecc_impacting_de_bw);
+
 	if (DISPLAY_VER(display) >= 30) {
 		if (DISPLAY_VERx100(display) == 3002)
 			tgl_get_bw_info(display, dram_info, &xe3lpd_3002_sa_info);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 354ef75ef6a5..5bf3b4ab2baa 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1233,6 +1233,7 @@
 #define   OROM_OFFSET_MASK			REG_GENMASK(20, 16)
 
 #define MTL_MEM_SS_INFO_GLOBAL			_MMIO(0x45700)
+#define   XE3P_ECC_IMPACTING_DE			REG_BIT(12)
 #define   MTL_N_OF_ENABLED_QGV_POINTS_MASK	REG_GENMASK(11, 8)
 #define   MTL_N_OF_POPULATED_CH_MASK		REG_GENMASK(7, 4)
 #define   MTL_DDR_TYPE_MASK			REG_GENMASK(3, 0)
diff --git a/drivers/gpu/drm/i915/soc/intel_dram.c b/drivers/gpu/drm/i915/soc/intel_dram.c
index 2e16346a6cc0..3e588762709a 100644
--- a/drivers/gpu/drm/i915/soc/intel_dram.c
+++ b/drivers/gpu/drm/i915/soc/intel_dram.c
@@ -686,6 +686,7 @@ static int gen12_get_dram_info(struct drm_i915_private *i915, struct dram_info *
 
 static int xelpdp_get_dram_info(struct drm_i915_private *i915, struct dram_info *dram_info)
 {
+	struct intel_display *display = i915->display;
 	u32 val = intel_uncore_read(&i915->uncore, MTL_MEM_SS_INFO_GLOBAL);
 
 	switch (REG_FIELD_GET(MTL_DDR_TYPE_MASK, val)) {
@@ -724,6 +725,9 @@ static int xelpdp_get_dram_info(struct drm_i915_private *i915, struct dram_info
 	dram_info->num_qgv_points = REG_FIELD_GET(MTL_N_OF_ENABLED_QGV_POINTS_MASK, val);
 	/* PSF GV points not supported in D14+ */
 
+	if (DISPLAY_VER(display) >= 35)
+		dram_info->ecc_impacting_de_bw = REG_FIELD_GET(XE3P_ECC_IMPACTING_DE, val);
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/soc/intel_dram.h b/drivers/gpu/drm/i915/soc/intel_dram.h
index 03a973f1c941..8475ee379daa 100644
--- a/drivers/gpu/drm/i915/soc/intel_dram.h
+++ b/drivers/gpu/drm/i915/soc/intel_dram.h
@@ -30,6 +30,7 @@ struct dram_info {
 	u8 num_channels;
 	u8 num_qgv_points;
 	u8 num_psf_gv_points;
+	bool ecc_impacting_de_bw; /* Only valid from Xe3p_LPD onward. */
 	bool symmetric_memory;
 	bool has_16gb_dimms;
 };

-- 
2.51.0