[Intel-gfx] [RFC PATCH 15/97] drm/i915/guc: Relax CTB response timeout

[Matthew Brost]

On Thu, May 06, 2021 at 12:13:29PM -0700, Matthew Brost wrote:
> From: Michal Wajdeczko <michal.wajdeczko at intel.com>
> 
> In upcoming patch we will allow more CTB requests to be sent in
> parallel to the GuC for procesing, so we shouldn't assume any more
> that GuC will always reply without 10ms.
> 
> Use bigger value from CONFIG_DRM_I915_HEARTBEAT_INTERVAL instead.
> 

I think this should be its own config option or we combine it with a
config option suggested in patch 37.

What do you think Michal? If you agree I can fix this up in the post of
these patches.

Matt

> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> index c87a0a8bef26..a4b2e7fe318b 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> @@ -436,17 +436,23 @@ static int ct_write(struct intel_guc_ct *ct,
>   */
>  static int wait_for_ct_request_update(struct ct_request *req, u32 *status)
>  {
> +	long timeout;
>  	int err;
>  
>  	/*
>  	 * Fast commands should complete in less than 10us, so sample quickly
>  	 * up to that length of time, then switch to a slower sleep-wait loop.
>  	 * No GuC command should ever take longer than 10ms.
> +	 *
> +	 * However, there might be other CT requests in flight before this one,
> +	 * so use @CONFIG_DRM_I915_HEARTBEAT_INTERVAL as backup timeout value.
>  	 */
> +	timeout = max(10, CONFIG_DRM_I915_HEARTBEAT_INTERVAL);
> +
>  #define done INTEL_GUC_MSG_IS_RESPONSE(READ_ONCE(req->status))
>  	err = wait_for_us(done, 10);
>  	if (err)
> -		err = wait_for(done, 10);
> +		err = wait_for(done, timeout);
>  #undef done
>  
>  	if (unlikely(err))
> -- 
> 2.28.0
>