Re: [PATCH v2] drm/xe/lrc: Restore CTX_CS_INDIRECT_CTX_OFFSET programming for ADL

[Helen Koike]

Hi Andi,

Thanks for your reply.

On 10/1/26 5:45 AM, Andi Shyti wrote:
> Hi Helen,
>
> On Wed, Sep 30, 2026 at 02:04:30PM -0300, Helen Koike wrote:
> > CTX_CS_INDIRECT_CTX_OFFSET default value is not retrieved from the GPU
> > by inhibit+context save mechanism since it is not part of the Engine
> > Context. Thus, at restore, 0x0 is programed back to the GPU, which is
>
> /programed/programmed/

Ack

> > an invalid value according to the PRM.
>
> ...
>
> >   	/*
> >   	 * Enable INDIRECT_CTX leaving INDIRECT_CTX_OFFSET at its default: it
> > -	 * varies per engine class, but the default is good enough
> > +	 * varies per engine class, but the default is good enough, except on
> > +	 * Alder Lake.
> >   	 */
> >   	xe_lrc_write_ctx_reg(lrc,
> >   			     CTX_CS_INDIRECT_CTX,
> >   			     (xe_bo_ggtt_addr(lrc->bo) + state.offset) |
> >   			     /* Size in CLs. */
> >   			     (state.written * sizeof(u32) / 64));
> > +	if (GRAPHICS_VER(lrc_to_xe(lrc)) < 20)
>
> Are you assuming that only Alder Lake is xe < 20?

This is a good point, since I was basing this patch on TGL PRM [1], I 
believe it should apply to all Gen12 gpus. Maybe I could s/for ADL/for 
Gen12, make sense? I only tested on ADL though.

[1] 
https://www.intel.com/content/www/us/en/docs/graphics-for-linux/developer-reference/1-0/tiger-lake.html

> As you are restoring the original code for render and compute,
> would it make sense also add a check for class being
> XE_EGINE_CLASS_RENDER || XE_ENGINE_CLASS_COMPUTE?

In my understanding from commit [2], indirect ctx will be allowed for 
other engines in the future, so I'm not sure we should limit here to 
those classes besides what gt_engine_needs_indirect_ctx() does.

[2] 
https://lore.kernel.org/all/20250916-wa-bb-cmds-v5-5-306bddbc15da@xxxxxxxxx/


Helen

> Andi
>
> > +		xe_lrc_write_ctx_reg(lrc,
> > +				     CTX_CS_INDIRECT_CTX_OFFSET,
> > +				     CTX_INDIRECT_CTX_OFFSET_DEFAULT);
> >   
> >   	return 0;
> >   }
> > --
> > 2.54.0