[PATCH 1/5] drm/i915: Disable compression tricks on JSL

[Andi Shyti]

Hi Ville,

On Mon, Jun 24, 2024 at 06:05:34PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Bspec asks us to disable some compression trick on JSL. While the
> bspec description is pretty vague it looks like this is some extra
> trick for 10bpc+ CCS which presumably the ICL derived display engine
> doesn't support.
> 
> Note that we aren't currently exposing 10bpc CCS scanout support,
> but once that gets added this presumably becomes an issue.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_regs.h     | 1 +
>  drivers/gpu/drm/i915/gt/intel_workarounds.c | 9 +++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> index e42b3a5d4e63..af53c40e6c21 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> @@ -432,6 +432,7 @@
>  #define XEHPG_INSTDONE_GEOM_SVG			MCR_REG(0x666c)
>  
>  #define CACHE_MODE_0_GEN7			_MMIO(0x7000) /* IVB+ */
> +#define   DISABLE_REPACKING_FOR_COMPRESSION	REG_BIT(15) /* jsl+ */

I know that REG_BIT() is the correct one, but for conformity I
would still use (1 << 15), otherwise we would have a mess of
styles.

Besides, you are breaking the order here.

>  #define   RC_OP_FLUSH_ENABLE			(1 << 0)
>  #define   HIZ_RAW_STALL_OPT_DISABLE		(1 << 2)
>  #define CACHE_MODE_1				_MMIO(0x7004) /* IVB+ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index 09a287c1aedd..a424b442493f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -2286,6 +2286,15 @@ rcs_engine_wa_init(struct intel_engine_cs *engine, struct i915_wa_list *wal)
>  			     GEN8_RC_SEMA_IDLE_MSG_DISABLE);
>  	}
>  
> +	if (IS_JASPERLAKE(i915) || IS_ELKHARTLAKE(i915)) {
> +		/*
> +		 * "Disable Repacking for Compression (masked R/W access)
> +		 *  before rendering compressed surfaces for display."
> +		 */
> +		wa_masked_en(wal, CACHE_MODE_0_GEN7,
> +			     DISABLE_REPACKING_FOR_COMPRESSION);

It is vague, indeed, but the description says that repacking
provides a boost in performance and "improvement in Lossless
Compression Algo" (whatever that means, I'm sailing in unknown
waters here :-) )

How did you get here?

Andi

> +	}
> +
>  	if (GRAPHICS_VER(i915) == 11) {
>  		/* This is not an Wa. Enable for better image quality */
>  		wa_masked_en(wal,
> -- 
> 2.44.2