[PATCH 3/3] drm/i915: Fix gt reset with GuC submission disabled

[Nirmoy Das]

Currently intel_gt_reset() happens as follows:

reset_prepare() ---> Sends GDRST to GuC, GuC is in GS_MIA_IN_RESET
do_reset()
  intel_gt_reset_all_engines()
    *_engine_reset_prepare() -->RESET_CTL expects running GuC
    *_reset_engines()
intel_gt_init_hw() --> GuC comes out of GS_MIA_IN_RESET with FW loaded.

Fix the issue by sanitizing the GuC only after resetting requested
engines and before intel_gt_init_hw().

Note intel_uc_reset_finish() and intel_uc_reset() are nop when
guc submission is disabled.

Signed-off-by: Nirmoy Das <nirmoy....@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_reset.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c 
b/drivers/gpu/drm/i915/gt/intel_reset.c
index 6504e8ba9c58..bd166f5aca4b 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -907,8 +907,17 @@ static intel_engine_mask_t reset_prepare(struct intel_gt 
*gt)
        intel_engine_mask_t awake = 0;
        enum intel_engine_id id;
 
-       /* For GuC mode, ensure submission is disabled before stopping ring */
-       intel_uc_reset_prepare(&gt->uc);
+       /**
+        * For GuC mode with submission enabled, ensure submission
+        * is disabled before stopping ring.
+        *
+        * For GuC mode with submission disabled, ensure that GuC is not
+        * sanitized, do that at the end in reset_finish(). reset_prepare()
+        * is followed by engine reset which in this mode requires GuC to
+        * be functional to process engine reset events.
+        */
+       if (intel_uc_uses_guc_submission(&gt->uc))
+               intel_uc_reset_prepare(&gt->uc);
 
        for_each_engine(engine, gt, id) {
                if (intel_engine_pm_get_if_awake(engine))
@@ -1255,6 +1264,9 @@ void intel_gt_reset(struct intel_gt *gt,
 
        intel_overlay_reset(gt->i915);
 
+       /* sanitize uC after engine reset */
+       if (!intel_uc_uses_guc_submission(&gt->uc))
+               intel_uc_reset_prepare(&gt->uc);
        /*
         * Next we need to restore the context, but we don't use those
         * yet either...
-- 
2.42.0