[PATCH v4 02/18] drm/panthor: Revisit the reset logic to avoid reset request loss

[Boris Brezillon]

disable/enable_work() provide a ready to use mechanism to temporarily
disable a work item, so use that instead of the complex state machinery
based on the PM state.

This also allows us to automate the reset resubmission in case a reset
was received while the work item was disabled.

Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/panthor/panthor_device.c | 36 +++++++++++++++++++++++++-------
 drivers/gpu/drm/panthor/panthor_device.h |  3 +--
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 7c55d0c45cfd..2974f4bc0bb1 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -181,6 +181,15 @@ static void panthor_device_free_page(struct drm_device *ddev, void *data)
 	__free_page(data);
 }
 
+static void enable_resets(struct panthor_device *ptdev)
+{
+	/* If a reset has been queued while the work was
+	 * disabled, reschedule it.
+	 */
+	if (enable_work(&ptdev->reset.work) && atomic_read(&ptdev->reset.pending))
+		queue_work(ptdev->reset.wq, &ptdev->reset.work);
+}
+
 int panthor_device_init(struct panthor_device *ptdev)
 {
 	u32 *dummy_page_virt;
@@ -256,6 +265,13 @@ int panthor_device_init(struct panthor_device *ptdev)
 
 	ptdev->phys_addr = res->start;
 
+	/* panthor_device_resume() calls enable_resets(), so we need to disable
+	 * the reset.work manually before this gets called to keep things
+	 * balanced. We don't bother re-enabling the work if the resume fails,
+	 * because the whole initialization will fail in that case, and the work
+	 * will vanish.
+	 */
+	disable_work(&ptdev->reset.work);
 	ret = devm_pm_runtime_enable(ptdev->base.dev);
 	if (ret)
 		return ret;
@@ -305,9 +321,6 @@ int panthor_device_init(struct panthor_device *ptdev)
 
 	panthor_gem_init(ptdev);
 
-	/* Now that everything is initialized, we can enable the reset work. */
-	enable_work(&ptdev->reset.work);
-
 	/* ~3 frames */
 	pm_runtime_set_autosuspend_delay(ptdev->base.dev, 50);
 	pm_runtime_use_autosuspend(ptdev->base.dev);
@@ -316,6 +329,9 @@ int panthor_device_init(struct panthor_device *ptdev)
 	if (ret)
 		goto err_disable_autosuspend;
 
+	/* Now that everything is initialized, we can enable the reset work. */
+	enable_resets(ptdev);
+
 	pm_runtime_put_autosuspend(ptdev->base.dev);
 	return 0;
 
@@ -534,10 +550,8 @@ int panthor_device_resume(struct device *dev)
 		/* If there was a reset pending at the time we suspended the
 		 * device, we force a slow reset.
 		 */
-		if (atomic_read(&ptdev->reset.pending)) {
+		if (atomic_cmpxchg(&ptdev->reset.pending, 1, 0))
 			ptdev->reset.fast = false;
-			atomic_set(&ptdev->reset.pending, 0);
-		}
 
 		ret = panthor_device_resume_hw_components(ptdev);
 		if (ret && ptdev->reset.fast) {
@@ -565,6 +579,9 @@ int panthor_device_resume(struct device *dev)
 			    DRM_PANTHOR_USER_MMIO_OFFSET, 0, 1);
 	atomic_set(&ptdev->pm.state, PANTHOR_DEVICE_PM_STATE_ACTIVE);
 	mutex_unlock(&ptdev->pm.mmio_lock);
+
+	/* Now that everything is resumed, we can re-enable the reset work. */
+	enable_resets(ptdev);
 	return 0;
 
 err_suspend_devfreq:
@@ -604,10 +621,13 @@ int panthor_device_suspend(struct device *dev)
 			    DRM_PANTHOR_USER_MMIO_OFFSET, 0, 1);
 	mutex_unlock(&ptdev->pm.mmio_lock);
 
+	/* Make sure we're not interrupted by resets after that point
+	 * until the GPU is resumed.
+	 */
+	disable_work_sync(&ptdev->reset.work);
+
 	if (panthor_device_is_initialized(ptdev) &&
 	    drm_dev_enter(&ptdev->base, &cookie)) {
-		cancel_work_sync(&ptdev->reset.work);
-
 		/* We prepare everything as if we were resetting the GPU.
 		 * The end of the reset will happen in the resume path though.
 		 */
diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 6529e01e838d..f55baa21b25e 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -389,8 +389,7 @@ void panthor_device_unplug(struct panthor_device *ptdev);
  */
 static inline void panthor_device_schedule_reset(struct panthor_device *ptdev)
 {
-	if (!atomic_cmpxchg(&ptdev->reset.pending, 0, 1) &&
-	    atomic_read(&ptdev->pm.state) == PANTHOR_DEVICE_PM_STATE_ACTIVE)
+	if (!atomic_cmpxchg(&ptdev->reset.pending, 0, 1))
 		queue_work(ptdev->reset.wq, &ptdev->reset.work);
 }
 

-- 
2.55.0