drm/panthor: Fix a race between the reset and suspend path

If a reset is scheduled when the suspend happens, we drop the
reset-pending info on the floor assuming the resume will fix things,
but the resume logic might try a fast reset. If we're lucky, the
fast reset fails and we fallback to a slow reset, but if the FW was
corrupted in a way that makes it partially functional (it boots but
doesn't quite do what it's expected to do), we won't notice immediately
that things are not working correctly, leading to a new reset further
down the road.

Fixes: 5fe909cae118 ("drm/panthor: Add the device logical block")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241217092457.1582053-1-boris.brezillon@collabora.com

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 0a37cfeeb181cbc48e72771ac7e4b3c5b55c96fc..a9da1d1eeb7071fb4fb7484f34becd4f9c5901d9 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -128,14 +128,11 @@ static void panthor_device_reset_work(struct work_struct *work)
        struct panthor_device *ptdev = container_of(work, struct panthor_device, reset.work);
        int ret = 0, cookie;
 
-       if (atomic_read(&ptdev->pm.state) != PANTHOR_DEVICE_PM_STATE_ACTIVE) {
-               /*
-                * No need for a reset as the device has been (or will be)
-                * powered down
-                */
-               atomic_set(&ptdev->reset.pending, 0);
+       /* If the device is entering suspend, we don't reset. A slow reset will
+        * be forced at resume time instead.
+        */
+       if (atomic_read(&ptdev->pm.state) != PANTHOR_DEVICE_PM_STATE_ACTIVE)
                return;
-       }
 
        if (!drm_dev_enter(&ptdev->base, &cookie))
                return;
@@ -477,6 +474,14 @@ int panthor_device_resume(struct device *dev)
 
        if (panthor_device_is_initialized(ptdev) &&
            drm_dev_enter(&ptdev->base, &cookie)) {
+               /* If there was a reset pending at the time we suspended the
+                * device, we force a slow reset.
+                */
+               if (atomic_read(&ptdev->reset.pending)) {
+                       ptdev->reset.fast = false;
+                       atomic_set(&ptdev->reset.pending, 0);
+               }
+
                ret = panthor_device_resume_hw_components(ptdev);
                if (ret && ptdev->reset.fast) {
                        drm_err(&ptdev->base, "Fast reset failed, trying a slow reset");
@@ -493,9 +498,6 @@ int panthor_device_resume(struct device *dev)
                        goto err_suspend_devfreq;
        }
 
-       if (atomic_read(&ptdev->reset.pending))
-               queue_work(ptdev->reset.wq, &ptdev->reset.work);
-
        /* Clear all IOMEM mappings pointing to this device after we've
         * resumed. This way the fake mappings pointing to the dummy pages
         * are removed and the real iomem mapping will be restored on next