[Intel-xe] [PATCH v2 07/11] drm/xe/gsc: Trigger a driver flr to cleanup the GSC on unload

[Daniele Ceraolo Spurio]

GSC is only killed by an FLR, so we need to trigger one on unload to
make sure we stop it. This is because we assign a chunk of memory to
the GSC as part of the FW load, so we need to make sure it stops
using it when we release it to the system on driver unload. Note that
this is not a problem of the unload per-se, because the GSC will not
touch that memory unless there are requests for it coming from the
driver; therefore, no accesses will happen while Xe is not loaded,
but if we re-load the driver then the GSC might wake up and try to
access that old memory location again.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Alan Previn <alan.previn.teres.alexis at intel.com>
Reviewed-by: John Harrison <John.C.Harrison at Intel.com>
---
 drivers/gpu/drm/xe/xe_gsc.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_gsc.c b/drivers/gpu/drm/xe/xe_gsc.c
index 0def7c1ae84d..1bb0de0a24f4 100644
--- a/drivers/gpu/drm/xe/xe_gsc.c
+++ b/drivers/gpu/drm/xe/xe_gsc.c
@@ -130,6 +130,23 @@ static int gsc_upload(struct xe_gsc *gsc)
 		return err;
 	}
 
+	/*
+	 * GSC is only killed by an FLR, so we need to trigger one on unload to
+	 * make sure we stop it. This is because we assign a chunk of memory to
+	 * the GSC as part of the FW load, so we need to make sure it stops
+	 * using it when we release it to the system on driver unload. Note that
+	 * this is not a problem of the unload per-se, because the GSC will not
+	 * touch that memory unless there are requests for it coming from the
+	 * driver; therefore, no accesses will happen while Xe is not loaded,
+	 * but if we re-load the driver then the GSC might wake up and try to
+	 * access that old memory location again.
+	 * Given that an FLR is a very disruptive action (see the FLR function
+	 * for details), we want to do it as the last action before releasing
+	 * the access to the MMIO bar, which means we need to do it as part of
+	 * mmio cleanup.
+	 */
+	xe->needs_flr_on_fini = true;
+
 	err = emit_gsc_upload(gsc);
 	if (err) {
 		xe_gt_err(gt, "Failed to emit GSC FW upload (%pe)\n", ERR_PTR(err));
-- 
2.41.0