drm/panthor: Fix the CONFIG_PM=n case

Putting a hard dependency on CONFIG_PM is not possible because of a
circular dependency issue, and it's actually not desirable either. In
order to support this use case, we forcibly resume at init time, and
suspend at unplug time.

v2:
- Drop the #ifdef CONFIG_PM section around panthor_pm_ops's definition
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403031944.EOimQ8WK-lkp@intel.com/Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240318153117.1321544-1-boris.brezillon@collabora.com

drivers/gpu/drm/panthor/panthor_device.c

@@ -87,6 +87,10 @@ void panthor_device_unplug(struct panthor_device *ptdev)
 	pm_runtime_dont_use_autosuspend(ptdev->base.dev);
 	pm_runtime_put_sync_suspend(ptdev->base.dev);
 
+	/* If PM is disabled, we need to call the suspend handler manually. */
+	if (!IS_ENABLED(CONFIG_PM))
+		panthor_device_suspend(ptdev->base.dev);
+
 	/* Report the unplug operation as done to unblock concurrent
 	 * panthor_device_unplug() callers.
 	 */
@@ -218,6 +222,13 @@ int panthor_device_init(struct panthor_device *ptdev)
 	if (ret)
 		return ret;
 
+	/* If PM is disabled, we need to call panthor_device_resume() manually. */
+	if (!IS_ENABLED(CONFIG_PM)) {
+		ret = panthor_device_resume(ptdev->base.dev);
+		if (ret)
+			return ret;
+	}
+
 	ret = panthor_gpu_init(ptdev);
 	if (ret)
 		goto err_rpm_put;
@@ -402,7 +413,6 @@ int panthor_device_mmap_io(struct panthor_device *ptdev, struct vm_area_struct *
 	return 0;
 }
 
-#ifdef CONFIG_PM
 int panthor_device_resume(struct device *dev)
 {
 	struct panthor_device *ptdev = dev_get_drvdata(dev);
@@ -547,4 +557,3 @@ int panthor_device_suspend(struct device *dev)
 	mutex_unlock(&ptdev->pm.mmio_lock);
 	return ret;
 }
-#endif

drivers/gpu/drm/panthor/panthor_drv.c

@@ -1417,7 +1417,7 @@ static struct platform_driver panthor_driver = {
 	.remove_new = panthor_remove,
 	.driver = {
 		.name = "panthor",
-		.pm = &panthor_pm_ops,
+		.pm = pm_ptr(&panthor_pm_ops),
 		.of_match_table = dt_match,
 	},
 };