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

[Matthew Auld <matthew.auld@intel.com>]

On 09/12/2021 15:45, Ramalingam C wrote:
> From: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
> 
> 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@intel.com>
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> ---
>   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 */
>