Re: [Intel-gfx] [PATCH] drm/i915: Fix indirect context size calculation

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Mika Kuoppala <mika.kuoppala@linux.intel.com> writes:

> Hardware needs cacheline count for indirect context size.
> Count of zero means that the feature is disabled.
> If we only divide size with cacheline bytes, we get
> one cacheline short of execution.
>
> Divide by rounding up to a cacheline size so that
> hardware executes everything intended.
>
> Bspec: 11739
> Fixes: 17ee950df38b ("drm/i915/gen8: Add infrastructure to initialize WA batch buffers")
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 6fbad5e2343f..acbb36ad17ff 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -4739,7 +4739,8 @@ static void init_wa_bb_reg_state(u32 * const regs,
>  
>  		regs[pos_bb_per_ctx + 2] =
>  			(ggtt_offset + wa_ctx->indirect_ctx.offset) |
> -			(wa_ctx->indirect_ctx.size / CACHELINE_BYTES);
> +			DIV_ROUND_UP(wa_ctx->indirect_ctx.size,
> +				     CACHELINE_BYTES);

The aligment to cacheline is checked on the emitting phase.

This patch can be ignored.
-Mika


>  
>  		regs[pos_bb_per_ctx + 4] =
>  			intel_lr_indirect_ctx_offset(engine) << 6;
> -- 
> 2.17.1
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