[PATCH 1/2] drm/i915/gt: Disable HW load balancing for CCS

[Matt Roper]

On Thu, Feb 15, 2024 at 02:59:23PM +0100, Andi Shyti wrote:
> The hardware should not dynamically balance the load between CCS
> engines. Wa_16016805146 recommends disabling it across all

Is this the right workaround number?  When I check the database, this
workaround was rejected on both DG2-G10 and DG2-G11, and doesn't even
have an entry for DG2-G12.

There are other workarounds that sound somewhat related to load
balancing (e.g., part 3 of Wa_14019159160), but what's asked there is
more involved than just setting one register bit and conflicts a bit
with the second patch of this series.


Matt

> platforms.
> 
> Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
> Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
> Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: <stable at vger.kernel.org> # v6.2+
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_regs.h     | 1 +
>  drivers/gpu/drm/i915/gt/intel_workarounds.c | 6 ++++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> index 50962cfd1353..cf709f6c05ae 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> @@ -1478,6 +1478,7 @@
>  
>  #define GEN12_RCU_MODE				_MMIO(0x14800)
>  #define   GEN12_RCU_MODE_CCS_ENABLE		REG_BIT(0)
> +#define   XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE	REG_BIT(1)
>  
>  #define CHV_FUSE_GT				_MMIO(VLV_GUNIT_BASE + 0x2168)
>  #define   CHV_FGT_DISABLE_SS0			(1 << 10)
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index d67d44611c28..7f42c8015f71 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -2988,6 +2988,12 @@ general_render_compute_wa_init(struct intel_engine_cs *engine, struct i915_wa_li
>  		wa_mcr_masked_en(wal, GEN8_HALF_SLICE_CHICKEN1,
>  				 GEN7_PSD_SINGLE_PORT_DISPATCH_ENABLE);
>  	}
> +
> +	/*
> +	 * Wa_16016805146: disable the CCS load balancing
> +	 * indiscriminately for all the platforms
> +	 */
> +	wa_masked_en(wal, GEN12_RCU_MODE, XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE);
>  }
>  
>  static void
> -- 
> 2.43.0
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation