[Intel-gfx] [PATCH] drm/i915/gt: Add separate MOCS table for Gen12 devices other than TGL/RKL

[Matt Roper]

On Tue, Sep 07, 2021 at 08:41:06PM +0300, Ville Syrjälä wrote:
> On Tue, Sep 07, 2021 at 10:27:28AM -0700, Matt Roper wrote:
> > On Tue, Sep 07, 2021 at 10:46:39PM +0530, Ayaz A Siddiqui wrote:
> > > MOCS table of TGL/RKL has MOCS[1] set to L3_UC.
> > > While for other gen12 devices we need to set MOCS[1] as L3_WB,
> > > So adding a new MOCS table for other gen 12 devices eg. ADL.
> > > 
> > > Fixes: cfbe5291a189 ("drm/i915/gt: Initialize unused MOCS entries with device specific values")
> > > Cc: Matt Roper <matthew.d.roper at intel.com>
> > > Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui at intel.com>
> > 
> > Yep, we overlooked that the TGL table still had an explicit entry for
> > I915_MOCS_PTE and wasn't just using an implicit 'unused_entries' lookup
> > for MOCS[1].  The new table is the same as the TGL table, just with
> > I915_MOCS_PTE (1) removed.
> 
> And just how are people planning on handling display cacheability
> control without a PTE MOCS entry? Is Mesa/etc. already making all
> external bos uncached on these platforms just in case we might
> scan out said bo?

MOCS entry 1 has never been considered a valid MOCS table entry on gen12
platforms (despite the old #define, it's not actually related to PTE,
display, etc. anymore).  Userspace shouldn't be using entry 1, since its
settings are officially undefined, but because we had already defined a
value for it in the driver on our production gen12 platforms (TGL/RKL),
we can't change that value now without an ABI break; we just have to
leave it be on TGL/RKL.

Any userspace trying to use entry 1 on gen12 (or any other undocumented
table entry) is still buggy and should still be updated.  For the gen12
platforms going forward (ADL-S, ADL-P, and anything else that shows up
in the future) we can just follow the guidance of setting all
invalid/unused entries as L3 cached from day 1.


Matt

> 
> > 
> > Looks good to me,
> > 
> > Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
> > 
> > 
> > > ---
> > >  drivers/gpu/drm/i915/gt/intel_mocs.c | 41 +++++++++++++++++++++++++---
> > >  1 file changed, 37 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
> > > index e96afd7beb49..c8d289b00de4 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_mocs.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
> > > @@ -315,6 +315,35 @@ static const struct drm_i915_mocs_entry dg1_mocs_table[] = {
> > >  	MOCS_ENTRY(63, 0, L3_1_UC),
> > >  };
> > >  
> > > +static const struct drm_i915_mocs_entry gen12_mocs_table[] = {
> > > +
> > > +	GEN11_MOCS_ENTRIES,
> > > +	/* Implicitly enable L1 - HDC:L1 + L3 + LLC */
> > > +	MOCS_ENTRY(48,
> > > +		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
> > > +		   L3_3_WB),
> > > +	/* Implicitly enable L1 - HDC:L1 + L3 */
> > > +	MOCS_ENTRY(49,
> > > +		   LE_1_UC | LE_TC_1_LLC,
> > > +		   L3_3_WB),
> > > +	/* Implicitly enable L1 - HDC:L1 + LLC */
> > > +	MOCS_ENTRY(50,
> > > +		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
> > > +		   L3_1_UC),
> > > +	/* Implicitly enable L1 - HDC:L1 */
> > > +	MOCS_ENTRY(51,
> > > +		   LE_1_UC | LE_TC_1_LLC,
> > > +		   L3_1_UC),
> > > +	/* HW Special Case (CCS) */
> > > +	MOCS_ENTRY(60,
> > > +		   LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
> > > +		   L3_1_UC),
> > > +	/* HW Special Case (Displayable) */
> > > +	MOCS_ENTRY(61,
> > > +		   LE_1_UC | LE_TC_1_LLC,
> > > +		   L3_3_WB),
> > > +};
> > > +
> > >  enum {
> > >  	HAS_GLOBAL_MOCS = BIT(0),
> > >  	HAS_ENGINE_MOCS = BIT(1),
> > > @@ -351,14 +380,18 @@ static unsigned int get_mocs_settings(const struct drm_i915_private *i915,
> > >  		table->n_entries = GEN9_NUM_MOCS_ENTRIES;
> > >  		table->uc_index = 1;
> > >  		table->unused_entries_index = 5;
> > > -	} else if (GRAPHICS_VER(i915) >= 12) {
> > > +	} else if (IS_TIGERLAKE(i915) || IS_ROCKETLAKE(i915)) {
> > > +		/* For TGL/RKL, Can't be changed now for ABI reasons */
> > >  		table->size  = ARRAY_SIZE(tgl_mocs_table);
> > >  		table->table = tgl_mocs_table;
> > >  		table->n_entries = GEN9_NUM_MOCS_ENTRIES;
> > >  		table->uc_index = 3;
> > > -		/* For TGL/RKL, Can't be changed now for ABI reasons */
> > > -		if (!IS_TIGERLAKE(i915) && !IS_ROCKETLAKE(i915))
> > > -			table->unused_entries_index = 2;
> > > +	} else if (GRAPHICS_VER(i915) >= 12) {
> > > +		table->size  = ARRAY_SIZE(gen12_mocs_table);
> > > +		table->table = gen12_mocs_table;
> > > +		table->n_entries = GEN9_NUM_MOCS_ENTRIES;
> > > +		table->uc_index = 3;
> > > +		table->unused_entries_index = 2;
> > >  	} else if (GRAPHICS_VER(i915) == 11) {
> > >  		table->size  = ARRAY_SIZE(icl_mocs_table);
> > >  		table->table = icl_mocs_table;
> > > -- 
> > > 2.26.2
> > > 
> > 
> > -- 
> > Matt Roper
> > Graphics Software Engineer
> > VTT-OSGC Platform Enablement
> > Intel Corporation
> > (916) 356-2795
> 
> -- 
> Ville Syrjälä
> Intel

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795