Re: [PATCH 18/22] drm/i915/tgl: Define MOCS entries for Tigerlake

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Jul 12, 2019 at 06:09:36PM -0700, Lucas De Marchi wrote:
> From: Tomasz Lis <tomasz.lis@intel.com>
> 
> The MOCS table is published as part of bspec, and versioned. Entries
> are supposed to never be modified, but new ones can be added. Adding
> entries increases table version. The patch includes version 1 entries.
> 
> Two of the 3 legacy entries used for gen9 are no longer expected to work.
> Although we are changing the gen11 table, those changes are supposed to
> be backward compatible since we are only touching previously undefined
> entries.
> 
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_mocs.c | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
> index 290a5e9b90b9..259e7bec0a63 100644
> --- a/drivers/gpu/drm/i915/gt/intel_mocs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
> @@ -62,6 +62,10 @@ struct drm_i915_mocs_table {
>  #define GEN11_NUM_MOCS_ENTRIES	64  /* 63-64 are reserved, but configured. */
>  
>  /* (e)LLC caching options */
> +/*
> + * Note: LE_0_PAGETABLE works only up to Gen11; for newer gens it means
> + * the same as LE_UC
> + */
>  #define LE_0_PAGETABLE		_LE_CACHEABILITY(0)
>  #define LE_1_UC			_LE_CACHEABILITY(1)
>  #define LE_2_WT			_LE_CACHEABILITY(2)
> @@ -100,8 +104,9 @@ struct drm_i915_mocs_table {
>   * of bspec.
>   *
>   * Entries not part of the following tables are undefined as far as
> - * userspace is concerned and shouldn't be relied upon.  For the time
> - * being they will be initialized to PTE.
> + * userspace is concerned and shouldn't be relied upon.  For Gen < 12
> + * they will be initialized to PTE. Gen >= 12 onwards don't have a setting for
> + * PTE. We use the same value, but that actually means Uncached.
>   *
>   * The last two entries are reserved by the hardware. For ICL+ they
>   * should be initialized according to bspec and never used, for older
> @@ -137,11 +142,13 @@ static const struct drm_i915_mocs_entry broxton_mocs_table[] = {
>  };
>  
>  #define GEN11_MOCS_ENTRIES \
> -	/* Base - Uncached (Deprecated) */ \
> +	/* Gen11: Base - Uncached (Deprecated) */ \
> +	/* Gen12+: Base - Error (Reserved for Non-Use) */ \
>  	MOCS_ENTRY(I915_MOCS_UNCACHED, \
>  		   LE_1_UC | LE_TC_1_LLC, \
>  		   L3_1_UC), \
>  	/* Base - L3 + LeCC:PAT (Deprecated) */ \
> +	/* Gen12+: Base - Reserved */ \
>  	MOCS_ENTRY(I915_MOCS_PTE, \
>  		   LE_0_PAGETABLE | LE_TC_1_LLC, \
>  		   L3_3_WB), \
> @@ -233,6 +240,18 @@ static const struct drm_i915_mocs_entry broxton_mocs_table[] = {
>  	MOCS_ENTRY(23, \
>  		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3) | LE_RSC(1) | LE_SCC(7), \
>  		   L3_3_WB), \
> +	/* Gen12+: HW Reserved - HDC:L1 + L3 + LLC */ \

Why is this marked as reserved? From the looks of things 48-61 should
just be normal entries that userspace can select to get HDC L1$. And
looks like icl already has that stuff. So someone should probably figure
out if Mesa/etc. can make use of the HDC L1$, and if so we should add
the relevant MOCS entries for icl as well.

> +	MOCS_ENTRY(48, \
> +		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
> +		   L3_3_WB), \
> +	/* Gen12+: HW Reserved - HW Special Case (CCS) */ \
> +	MOCS_ENTRY(60, \
> +		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
> +		   L3_1_UC), \
> +	/* Gen12+: HW Reserved - HW Special Case (Displayable) */ \
> +	MOCS_ENTRY(61, \
> +		   LE_1_UC | LE_TC_1_LLC | LE_SCF(1), \
> +		   L3_3_WB), \
>  	/* HW Reserved - SW program but never use */ \
>  	MOCS_ENTRY(62, \
>  		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
> -- 
> 2.21.0

-- 
Ville Syrjälä
Intel
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