Re: [PATCH v5] drm/i915/mtl: enable local stolen memory

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On Thu, Sep 29, 2022 at 05:16:58PM +0530, Aravind Iddamsetty wrote:
> As an integrated GPU, MTL does not have local memory and HAS_LMEM()
> returns false.  However the platform's stolen memory is presented via
> BAR2 (i.e., the BAR we traditionally consider to be the GMADR on IGFX)
> and should be managed by the driver the same way that local memory is
> on dgpu platforms (which includes setting the "lmem" bit on page table
> entries).  We use the term "local stolen memory" to refer to this
> model.
> 
> The major difference from the traditional BAR2 (GMADR) is that
> the stolen area is mapped via the BAR2 while in the former BAR2 is an
> aperture into the GTT VA through which access are made into stolen area.
> 
> BSPEC: 53098, 63830
> 
> v2:
> 1. dropped is_dsm_invalid, updated valid_stolen_size check from Lucas
> (Jani, Lucas)
> 2. drop lmembar_is_igpu_stolen
> 3. revert to referring GFXMEM_BAR as GEN12_LMEM_BAR (Lucas)
> 
> v3:(Jani)
> 1. rename get_mtl_gms_size to mtl_get_gms_size
> 2. define register for MMIO address
> 
> v4:(Matt)
> 1. Use REG_FIELD_GET to read GMS value
> 2. replace the calculations with SZ_256M/SZ_8M
> 
> v5: Include more details to commit message on how it is different from
> earlier platforms (Anshuman)
> 
> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> 
> Signed-off-by: CQ Tang <cq.tang@xxxxxxxxx>
> Signed-off-by: Aravind Iddamsetty <aravind.iddamsetty@xxxxxxxxx>
> Original-author: CQ Tang

Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>

> ---
>  drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 83 ++++++++++++++++++----
>  drivers/gpu/drm/i915/gt/intel_ggtt.c       |  2 +-
>  drivers/gpu/drm/i915/i915_drv.h            |  3 +
>  drivers/gpu/drm/i915/i915_reg.h            |  4 ++
>  4 files changed, 76 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> index c5a4035c99cd..910086974454 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
> @@ -77,9 +77,9 @@ void i915_gem_stolen_remove_node(struct drm_i915_private *i915,
>  	mutex_unlock(&i915->mm.stolen_lock);
>  }
>  
> -static bool valid_stolen_size(struct resource *dsm)
> +static bool valid_stolen_size(struct drm_i915_private *i915, struct resource *dsm)
>  {
> -	return dsm->start != 0 && dsm->end > dsm->start;
> +	return (dsm->start != 0 || HAS_BAR2_SMEM_STOLEN(i915)) && dsm->end > dsm->start;
>  }
>  
>  static int adjust_stolen(struct drm_i915_private *i915,
> @@ -88,7 +88,7 @@ static int adjust_stolen(struct drm_i915_private *i915,
>  	struct i915_ggtt *ggtt = to_gt(i915)->ggtt;
>  	struct intel_uncore *uncore = ggtt->vm.gt->uncore;
>  
> -	if (!valid_stolen_size(dsm))
> +	if (!valid_stolen_size(i915, dsm))
>  		return -EINVAL;
>  
>  	/*
> @@ -135,7 +135,7 @@ static int adjust_stolen(struct drm_i915_private *i915,
>  		}
>  	}
>  
> -	if (!valid_stolen_size(dsm))
> +	if (!valid_stolen_size(i915, dsm))
>  		return -EINVAL;
>  
>  	return 0;
> @@ -149,8 +149,11 @@ static int request_smem_stolen(struct drm_i915_private *i915,
>  	/*
>  	 * With stolen lmem, we don't need to request system memory for the
>  	 * address range since it's local to the gpu.
> +	 *
> +	 * Starting MTL, in IGFX devices the stolen memory is exposed via
> +	 * BAR2 and shall be considered similar to stolen lmem.
>  	 */
> -	if (HAS_LMEM(i915))
> +	if (HAS_LMEM(i915) || HAS_BAR2_SMEM_STOLEN(i915))
>  		return 0;
>  
>  	/*
> @@ -385,8 +388,6 @@ static void icl_get_stolen_reserved(struct drm_i915_private *i915,
>  
>  	drm_dbg(&i915->drm, "GEN6_STOLEN_RESERVED = 0x%016llx\n", reg_val);
>  
> -	*base = reg_val & GEN11_STOLEN_RESERVED_ADDR_MASK;
> -
>  	switch (reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK) {
>  	case GEN8_STOLEN_RESERVED_1M:
>  		*size = 1024 * 1024;
> @@ -404,6 +405,12 @@ static void icl_get_stolen_reserved(struct drm_i915_private *i915,
>  		*size = 8 * 1024 * 1024;
>  		MISSING_CASE(reg_val & GEN8_STOLEN_RESERVED_SIZE_MASK);
>  	}
> +
> +	if (HAS_BAR2_SMEM_STOLEN(i915))
> +		/* the base is initialized to stolen top so subtract size to get base */
> +		*base -= *size;
> +	else
> +		*base = reg_val & GEN11_STOLEN_RESERVED_ADDR_MASK;
>  }
>  
>  /*
> @@ -833,6 +840,29 @@ static const struct intel_memory_region_ops i915_region_stolen_lmem_ops = {
>  	.init_object = _i915_gem_object_stolen_init,
>  };
>  
> +static int mtl_get_gms_size(struct intel_uncore *uncore)
> +{
> +	u16 ggc, gms;
> +
> +	ggc = intel_uncore_read16(uncore, GGC);
> +
> +	/* check GGMS, should be fixed 0x3 (8MB) */
> +	if ((ggc & GGMS_MASK) != GGMS_MASK)
> +		return -EIO;
> +
> +	/* return valid GMS value, -EIO if invalid */
> +	gms = REG_FIELD_GET(GMS_MASK, ggc);
> +	switch (gms) {
> +	case 0x0 ... 0x04:
> +		return gms * 32;
> +	case 0xf0 ... 0xfe:
> +		return (gms - 0xf0 + 1) * 4;
> +	default:
> +		MISSING_CASE(gms);
> +		return -EIO;
> +	}
> +}
> +
>  struct intel_memory_region *
>  i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
>  			   u16 instance)
> @@ -843,6 +873,7 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
>  	struct intel_memory_region *mem;
>  	resource_size_t io_start, io_size;
>  	resource_size_t min_page_size;
> +	int ret;
>  
>  	if (WARN_ON_ONCE(instance))
>  		return ERR_PTR(-ENODEV);
> @@ -850,12 +881,8 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
>  	if (!i915_pci_resource_valid(pdev, GEN12_LMEM_BAR))
>  		return ERR_PTR(-ENXIO);
>  
> -	/* Use DSM base address instead for stolen memory */
> -	dsm_base = intel_uncore_read64(uncore, GEN12_DSMBASE) & GEN12_BDSM_MASK;
> -	if (IS_DG1(uncore->i915)) {
> +	if (HAS_BAR2_SMEM_STOLEN(i915) || IS_DG1(i915)) {
>  		lmem_size = pci_resource_len(pdev, GEN12_LMEM_BAR);
> -		if (WARN_ON(lmem_size < dsm_base))
> -			return ERR_PTR(-ENODEV);
>  	} else {
>  		resource_size_t lmem_range;
>  
> @@ -864,13 +891,39 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
>  		lmem_size *= SZ_1G;
>  	}
>  
> -	dsm_size = lmem_size - dsm_base;
> -	if (pci_resource_len(pdev, GEN12_LMEM_BAR) < lmem_size) {
> +	if (HAS_BAR2_SMEM_STOLEN(i915)) {
> +		/*
> +		 * MTL dsm size is in GGC register.
> +		 * Also MTL uses offset to DSMBASE in ptes, so i915
> +		 * uses dsm_base = 0 to setup stolen region.
> +		 */
> +		ret = mtl_get_gms_size(uncore);
> +		if (ret < 0) {
> +			drm_err(&i915->drm, "invalid MTL GGC register setting\n");
> +			return ERR_PTR(ret);
> +		}
> +
> +		dsm_base = 0;
> +		dsm_size = (resource_size_t)(ret * SZ_1M);
> +
> +		GEM_BUG_ON(pci_resource_len(pdev, GEN12_LMEM_BAR) != SZ_256M);
> +		GEM_BUG_ON((dsm_size + SZ_8M) > lmem_size);
> +	} else {
> +		/* Use DSM base address instead for stolen memory */
> +		dsm_base = intel_uncore_read64(uncore, GEN12_DSMBASE);
> +		if (WARN_ON(lmem_size < dsm_base))
> +			return ERR_PTR(-ENODEV);
> +		dsm_size = lmem_size - dsm_base;
> +	}
> +
> +	io_size = dsm_size;
> +	if (pci_resource_len(pdev, GEN12_LMEM_BAR) < dsm_size) {
>  		io_start = 0;
>  		io_size = 0;
> +	} else if (HAS_BAR2_SMEM_STOLEN(i915)) {
> +		io_start = pci_resource_start(pdev, GEN12_LMEM_BAR) + SZ_8M;
>  	} else {
>  		io_start = pci_resource_start(pdev, GEN12_LMEM_BAR) + dsm_base;
> -		io_size = dsm_size;
>  	}
>  
>  	min_page_size = HAS_64K_PAGES(i915) ? I915_GTT_PAGE_SIZE_64K :
> diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> index 30cf5c3369d9..b31fe0fb013f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> @@ -931,7 +931,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
>  	unsigned int size;
>  	u16 snb_gmch_ctl;
>  
> -	if (!HAS_LMEM(i915)) {
> +	if (!HAS_LMEM(i915) && !HAS_BAR2_SMEM_STOLEN(i915)) {
>  		if (!i915_pci_resource_valid(pdev, GTT_APERTURE_BAR))
>  			return -ENXIO;
>  
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 84a2f6b16f57..90ed8e6db2fe 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -974,6 +974,9 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
>  
>  #define HAS_ONE_EU_PER_FUSE_BIT(i915)	(INTEL_INFO(i915)->has_one_eu_per_fuse_bit)
>  
> +#define HAS_BAR2_SMEM_STOLEN(i915) (!HAS_LMEM(i915) && \
> +				    GRAPHICS_VER_FULL(i915) >= IP_VER(12, 70))
> +
>  /* intel_device_info.c */
>  static inline struct intel_device_info *
>  mkwrite_device_info(struct drm_i915_private *dev_priv)
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 5003a5ffbc6a..2126e441199d 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7967,6 +7967,10 @@ enum skl_power_gate {
>  							   _ICL_PIPE_DSS_CTL2_PB, \
>  							   _ICL_PIPE_DSS_CTL2_PC)
>  
> +#define GGC				_MMIO(0x108040)
> +#define   GMS_MASK			REG_GENMASK(15, 8)
> +#define   GGMS_MASK			REG_GENMASK(7, 6)
> +
>  #define GEN12_GSMBASE			_MMIO(0x108100)
>  #define GEN12_DSMBASE			_MMIO(0x1080C0)
>  #define   GEN12_BDSM_MASK		REG_GENMASK64(63, 20)
> -- 
> 2.25.1
> 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation



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