[PATCH] drm/i915/gsc: Fix the Driver-FLR completion

[Alan Previn]

The Driver-FLR flow may inadvertently exit early before the full
completion of the re-init of the internal HW state if we only poll
GU_DEBUG Bit31 (polling for it to toggle from 0 -> 1). Instead
we need a two-step completion wait-for-completion flow that also
involves GU_CNTL. See the patch and new code comments for detail.
This is new direction from HW architecture folks.

   v2: - Add error message for the teardown timeout (Anshuman)
       - Don't duplicate code in comments (Jani)
   v3: - Add get/put runtime-pm for this function. Though
         not functionally required during unload, its so the uncore
         doesn't complain.

Signed-off-by: Alan Previn <alan.previn.teres.ale...@intel.com>
Fixes: 5a44fcd73498 ("drm/i915/gsc: Do a driver-FLR on unload if GSC was 
loaded")
---
 drivers/gpu/drm/i915/intel_uncore.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c 
b/drivers/gpu/drm/i915/intel_uncore.c
index f018da7ebaac..9832b8ac8b1a 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -2724,10 +2724,13 @@ static void driver_initiated_flr(struct intel_uncore 
*uncore)
 {
        struct drm_i915_private *i915 = uncore->i915;
        const unsigned int flr_timeout_ms = 3000; /* specs recommend a 3s wait 
*/
+       intel_wakeref_t wakeref;
        int ret;
 
        drm_dbg(&i915->drm, "Triggering Driver-FLR\n");
 
+       wakeref = intel_runtime_pm_get(&i915->runtime_pm);
+
        /*
         * Make sure any pending FLR requests have cleared by waiting for the
         * FLR trigger bit to go to zero. Also clear GU_DEBUG's DRIVERFLR_STATUS
@@ -2742,22 +2745,36 @@ static void driver_initiated_flr(struct intel_uncore 
*uncore)
                drm_err(&i915->drm,
                        "Failed to wait for Driver-FLR bit to clear! %d\n",
                        ret);
-               return;
+               goto out;
        }
        intel_uncore_write_fw(uncore, GU_DEBUG, DRIVERFLR_STATUS);
 
        /* Trigger the actual Driver-FLR */
        intel_uncore_rmw_fw(uncore, GU_CNTL, 0, DRIVERFLR);
 
+       /* Wait for hardware teardown to complete */
+       ret = intel_wait_for_register_fw(uncore, GU_CNTL,
+                                        DRIVERFLR_STATUS, 0,
+                                        flr_timeout_ms);
+       if (ret) {
+               drm_err(&i915->drm, "Driver-FLR-teardown wait completion 
failed! %d\n", ret);
+               goto out;
+       }
+
+       /* Wait for hardware/firmware re-init to complete */
        ret = intel_wait_for_register_fw(uncore, GU_DEBUG,
                                         DRIVERFLR_STATUS, DRIVERFLR_STATUS,
                                         flr_timeout_ms);
        if (ret) {
-               drm_err(&i915->drm, "wait for Driver-FLR completion failed! 
%d\n", ret);
-               return;
+               drm_err(&i915->drm, "Driver-FLR-reinit wait completion failed! 
%d\n", ret);
+               goto out;
        }
 
+       /* Clear sticky completion status */
        intel_uncore_write_fw(uncore, GU_DEBUG, DRIVERFLR_STATUS);
+
+out:
+       intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 }
 
 /* Called via drm-managed action */
-- 
2.39.0