[Intel-gfx] [PATCH 02/12] drm/i915/guc: Keep the ctx_pool_vaddr mapped, for easy access

[Chris Wilson]

On Tue, Mar 21, 2017 at 02:02:47AM -0700, Oscar Mateo wrote:
> The GuC descriptor is big in size. If we use a local definition of
> guc_desc we have a chance to overflow stack, so avoid it.
> 
> Also, Chris abhors scatterlists :)
> 
> v2: Rebased, helper function to retrieve the context descriptor,
> s/ctx_pool_vma/ctx_pool/
> 
> v3: Zero out guc_context_desc before initialization
> 
> v4: Do not do arithmetic on void pointers
> 
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_guc_submission.c | 93 +++++++++++++++---------------
>  drivers/gpu/drm/i915/intel_guc_loader.c    |  2 +-
>  drivers/gpu/drm/i915/intel_uc.h            |  3 +-
>  3 files changed, 48 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 21dadc1..5870cec 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -133,6 +133,12 @@ static int __guc_deallocate_doorbell(struct intel_guc *guc, u32 ctx_index)
>  	return intel_guc_send(guc, action, ARRAY_SIZE(action));
>  }
>  
> +static struct guc_context_desc *__get_context_desc(struct i915_guc_client *client)
> +{
> +	return (struct guc_context_desc *)((char *)client->guc->ctx_pool_vaddr +

We can use gccisms like using void * for arithmetic computations in the
kernel, i.e.
	void *base = client->guc->ctx_pool_vaddr;
	return base + sizeof(struct guc_context_desc) * client->ctx_index;
is just fine.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre