Re: [PATCH v2 6/6] drm/xe/guc: Allow second H2G retry on FLR

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Jan 27, 2026 at 08:37:26PM +0100, Michal Wajdeczko wrote:
> During VF FLR the scratch registers could be cleared both by the
> GuC and by the PF driver. Allow to retry more times once we find
> out that the HXG header was cleared and wait at least 256ms before
> resending the same message again to the GuC.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
> v2: rebased
> ---
>  drivers/gpu/drm/xe/xe_guc.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
> index 231844bce1e0..70ce1d7aec21 100644
> --- a/drivers/gpu/drm/xe/xe_guc.c
> +++ b/drivers/gpu/drm/xe/xe_guc.c
> @@ -1389,6 +1389,9 @@ int xe_guc_auth_huc(struct xe_guc *guc, u32 rsa_addr)
>  	return xe_guc_ct_send_block(&guc->ct, action, ARRAY_SIZE(action));
>  }
>  
> +#define MAX_RETRIES_ON_FLR	2
> +#define MIN_SLEEP_MS_ON_FLR	256
> +
>  int xe_guc_mmio_send_recv(struct xe_guc *guc, const u32 *request,
>  			  u32 len, u32 *response_buf)
>  {
> @@ -1399,7 +1402,7 @@ int xe_guc_mmio_send_recv(struct xe_guc *guc, const u32 *request,
>  		MED_VF_SW_FLAG(0) : VF_SW_FLAG(0);
>  	const u32 LAST_INDEX = VF_SW_FLAG_COUNT - 1;
>  	unsigned int sleep_period_ms = 1;
> -	bool lost = false;
> +	unsigned int lost = 0;
>  	u32 header;
>  	int ret;
>  	int i;
> @@ -1435,9 +1438,14 @@ int xe_guc_mmio_send_recv(struct xe_guc *guc, const u32 *request,
>  			     50000, &header, false);
>  	if (ret) {
>  		/* scratch registers might be cleared during FLR, try once more */
> -		if (!header && !lost) {
> +		if (!header) {
> +			if (++lost > MAX_RETRIES_ON_FLR) {
> +				xe_gt_err(gt, "GuC mmio request %#x: lost, too many retries %u\n",
> +					  request[0], lost);
> +				return -ENOLINK;
> +			}
>  			xe_gt_dbg(gt, "GuC mmio request %#x: lost, trying again\n", request[0]);
> -			lost = true;
> +			xe_sleep_relaxed_ms(MIN_SLEEP_MS_ON_FLR);
>  			goto retry;
>  		}
>  timeout:
> -- 
> 2.47.1
>