Re: [PATCH v4 05/16] drm/i915/lmem: Enable lmem for platforms with Flat CCS

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On 09/12/2021 15:45, Ramalingam C wrote:
From: Abdiel Janulgue <abdiel.janulgue@xxxxxxxxxxxxxxx>

A portion of device memory is reserved for Flat CCS so usable
device memory will be reduced by size of Flat CCS. Size of
Flat CCS is specified in “XEHPSDV_FLAT_CCS_BASE_ADDR”.
So to get effective device memory we need to subtract
total device memory by Flat CCS memory size.

Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@xxxxxxxxxxxxxxx>
Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx>
---
  drivers/gpu/drm/i915/gt/intel_gt.c          | 19 ++++++++++++++++++
  drivers/gpu/drm/i915/gt/intel_gt.h          |  1 +
  drivers/gpu/drm/i915/gt/intel_region_lmem.c | 22 +++++++++++++++++++--
  drivers/gpu/drm/i915/i915_reg.h             |  3 +++
  4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index f2422d48be32..510cda6a163f 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -902,6 +902,25 @@ u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg)
  	return intel_uncore_read_fw(gt->uncore, reg);
  }
+u32 intel_gt_read_register(struct intel_gt *gt, i915_reg_t reg)
+{
+	int type;
+	u8 sliceid, subsliceid;
+
+	for (type = 0; type < NUM_STEERING_TYPES; type++) {
+		if (intel_gt_reg_needs_read_steering(gt, reg, type)) {
+			intel_gt_get_valid_steering(gt, type, &sliceid,
+						    &subsliceid);
+			return intel_uncore_read_with_mcr_steering(gt->uncore,
+								   reg,
+								   sliceid,
+								   subsliceid);
+		}
+	}
+
+	return intel_uncore_read(gt->uncore, reg);
+}
+
  void intel_gt_info_print(const struct intel_gt_info *info,
  			 struct drm_printer *p)
  {
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
index 74e771871a9b..24b78398a587 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt.h
@@ -84,6 +84,7 @@ static inline bool intel_gt_needs_read_steering(struct intel_gt *gt,
  }
u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg);
+u32 intel_gt_read_register(struct intel_gt *gt, i915_reg_t reg);
void intel_gt_info_print(const struct intel_gt_info *info,
  			 struct drm_printer *p);
diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
index fde2dcb59809..a358fa14372b 100644
--- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
+++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
@@ -205,8 +205,26 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
  	if (!IS_DGFX(i915))
  		return ERR_PTR(-ENODEV);
- /* Stolen starts from GSMBASE on DG1 */
-	lmem_size = intel_uncore_read64(uncore, GEN12_GSMBASE);
+	if (HAS_FLAT_CCS(i915)) {
+		u64 tile_stolen, flat_ccs_base_addr_reg, flat_ccs_base;
+
+		lmem_size = pci_resource_len(pdev, 2);

Should we check if lmem_size < tile_stolen somewhere? I think I have seen that with 256M BAR. Maybe just return -ENODEV, for now?

+		flat_ccs_base_addr_reg = intel_gt_read_register(gt, XEHPSDV_FLAT_CCS_BASE_ADDR);
+		flat_ccs_base = (flat_ccs_base_addr_reg >> XEHPSDV_CCS_BASE_SHIFT) * SZ_64K;
+		tile_stolen = lmem_size - flat_ccs_base;
+
+		/* If the FLAT_CCS_BASE_ADDR register is not populated, flag an error */
+		if (tile_stolen == lmem_size)
+			DRM_ERROR("CCS_BASE_ADDR register did not have expected value\n");
+
+		lmem_size -= tile_stolen;
+	} else {
+		/* Stolen starts from GSMBASE without CCS */
+		lmem_size = intel_uncore_read64(&i915->uncore, GEN12_GSMBASE);
+		if (GEM_WARN_ON(lmem_size > pci_resource_len(pdev, 2)))
+			return ERR_PTR(-ENODEV);

We also have this check below. I guess just set the lmem_size here?

+	}
+
io_start = pci_resource_start(pdev, 2);
  	if (GEM_WARN_ON(lmem_size > pci_resource_len(pdev, 2)))
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d27ba273cc68..29f1cafb0f4b 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -12620,6 +12620,9 @@ enum skl_power_gate {
  #define   SGGI_DIS			REG_BIT(15)
  #define   SGR_DIS			REG_BIT(13)
+#define XEHPSDV_FLAT_CCS_BASE_ADDR _MMIO(0x4910)
+#define   XEHPSDV_CCS_BASE_SHIFT               8
+
  /* gamt regs */
  #define GEN8_L3_LRA_1_GPGPU _MMIO(0x4dd4)
  #define   GEN8_L3_LRA_1_GPGPU_DEFAULT_VALUE_BDW  0x67F1427F /* max/min for LRA1/2 */




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