[PATCH v3 2/2] drm/xe/vf: Retry sending MMIO request to GUC on timeout error

[Satyanarayana K V P]

Add support to allow retrying the sending of MMIO requests
from the VF to the GUC in the event of an error. During the
suspend/resume process, VFs begin resuming only after the PF has
resumed. Although the PF resumes, the GUC reset and provisioning
occur later in a separate worker process.

When there are a large number of VFs, some may attempt to resume
before the PF has completed its provisioning. Therefore, if a
MMIO request from a VF fails during this period, we will retry
sending the request up to GUC_RESET_VF_STATE_RETRY_MAX times,
which is set to a maximum of 10 attempts.

Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p at intel.com>
Cc: Michał Wajdeczko <michal.wajdeczko at intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski at intel.com>
Reviewed-by: Piotr Piorkowski <piotr.piorkowski at intel.com>
---
 drivers/gpu/drm/xe/xe_gt_sriov_vf.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
index 4831549da319..a439261bf4d7 100644
--- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
+++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
@@ -47,12 +47,19 @@ static int guc_action_vf_reset(struct xe_guc *guc)
 	return ret > 0 ? -EPROTO : ret;
 }
 
+#define GUC_RESET_VF_STATE_RETRY_MAX	10
 static int vf_reset_guc_state(struct xe_gt *gt)
 {
+	unsigned int retry = GUC_RESET_VF_STATE_RETRY_MAX;
 	struct xe_guc *guc = &gt->uc.guc;
 	int err;
 
-	err = guc_action_vf_reset(guc);
+	do {
+		err = guc_action_vf_reset(guc);
+		if (!err || err != -ETIMEDOUT)
+			break;
+	} while (--retry);
+
 	if (unlikely(err))
 		xe_gt_sriov_err(gt, "Failed to reset GuC state (%pe)\n", ERR_PTR(err));
 	return err;
-- 
2.35.3