drm/xe/guc: Resend potentially lost H2G MMIO request

There could be a scenario where the VF driver is resuming faster
than the driver PF is able to complete the VF FLR sequence which
includes reset of the VF scratch registers.  This may result in
deletion of the ongoing HXG message (it could be either a host
request or a GuC response).

When we detect that HXG message was likey lost (scratch register
with HXG header was zeroed) try to send this request once more
before giving up.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Reviewed-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Link: https://lore.kernel.org/r/20250528090021.329-1-michal.wajdeczko@intel.com

diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
index 350434a8b9537224ff37e087c28b4288dba55e56..52453845d1bd311110e2a08ab4695017b9d18a91 100644 (file)
--- a/drivers/gpu/drm/xe/xe_guc.c
+++ b/drivers/gpu/drm/xe/xe_guc.c
@@ -1289,6 +1289,7 @@ int xe_guc_mmio_send_recv(struct xe_guc *guc, const u32 *request,
        struct xe_reg reply_reg = xe_gt_is_media_type(gt) ?
                MED_VF_SW_FLAG(0) : VF_SW_FLAG(0);
        const u32 LAST_INDEX = VF_SW_FLAG_COUNT - 1;
+       bool lost = false;
        int ret;
        int i;
 
@@ -1322,6 +1323,12 @@ retry:
                             FIELD_PREP(GUC_HXG_MSG_0_ORIGIN, GUC_HXG_ORIGIN_GUC),
                             50000, &reply, false);
        if (ret) {
+               /* scratch registers might be cleared during FLR, try once more */
+               if (!reply && !lost) {
+                       xe_gt_dbg(gt, "GuC mmio request %#x: lost, trying again\n", request[0]);
+                       lost = true;
+                       goto retry;
+               }
 timeout:
                xe_gt_err(gt, "GuC mmio request %#x: no reply %#x\n",
                          request[0], reply);