Revert "firmware: add sanity check on shutdown/suspend"

This reverts commit 81f95076281fdd3bc382e004ba1bce8e82fccbce.

It causes random failures of firmware loading at resume time (well,
random for me, it seems to be more reliable for others) because the
firmware disabling is not actually synchronous with any particular
resume event, and at least the btusb driver that uses a workqueue to
load the firmware at resume seems to occasionally hit the "firmware
loading is disabled" logic because the firmware loader hasn't gotten the
resume event yet.

Some kind of sanity check for not trying to load firmware when it's not
possible might be a good thing, but this commit was not it.

Greg seems to have silently suffered the same issue, and pointed to the
likely culprit, and Gabriel C verified the revert fixed it for him too.

Reported-by: Linus Torvalds <[e-mail]>
Pointed-at-by: Greg Kroah-Hartman <[e-mail]>
Tested-by: Gabriel C <[e-mail]>
Cc: Luis R. Rodriguez <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/driver-api/firmware/request_firmware.rst

···
 .. kernel-doc:: drivers/base/firmware_class.c
    :functions: request_firmware_nowait
 
-Considerations for suspend and resume
-=====================================
-
-During suspend and resume only the built-in firmware and the firmware cache
-elements of the firmware API can be used. This is managed by fw_pm_notify().
-
-fw_pm_notify
-------------
-.. kernel-doc:: drivers/base/firmware_class.c
-   :functions: fw_pm_notify
-
 request firmware API expected driver use
 ========================================
 

drivers/base/firmware_class.c

···
  * guarding for corner cases a global lock should be OK */
 static DEFINE_MUTEX(fw_lock);
 
-static bool __enable_firmware = false;
-
-static void enable_firmware(void)
-{
-	mutex_lock(&fw_lock);
-	__enable_firmware = true;
-	mutex_unlock(&fw_lock);
-}
-
-static void disable_firmware(void)
-{
-	mutex_lock(&fw_lock);
-	__enable_firmware = false;
-	mutex_unlock(&fw_lock);
-}
-
-/*
- * When disabled only the built-in firmware and the firmware cache will be
- * used to look for firmware.
- */
-static bool firmware_enabled(void)
-{
-	bool enabled = false;
-
-	mutex_lock(&fw_lock);
-	if (__enable_firmware)
-		enabled = true;
-	mutex_unlock(&fw_lock);
-
-	return enabled;
-}
-
 static struct firmware_cache fw_cache;
 
 static struct firmware_buf *__allocate_fw_buf(const char *fw_name,
···
 	if (ret <= 0) /* error or already assigned */
 		goto out;
 
-	if (!firmware_enabled()) {
-		WARN(1, "firmware request while host is not available\n");
-		ret = -EHOSTDOWN;
-		goto out;
-	}
-
 	ret = fw_get_filesystem_firmware(device, fw->priv);
 	if (ret) {
 		if (!(opt_flags & FW_OPT_NO_WARN))
···
 			   msecs_to_jiffies(delay));
 }
 
-/**
- * fw_pm_notify - notifier for suspend/resume
- * @notify_block: unused
- * @mode: mode we are switching to
- * @unused: unused
- *
- * Used to modify the firmware_class state as we move in between states.
- * The firmware_class implements a firmware cache to enable device driver
- * to fetch firmware upon resume before the root filesystem is ready. We
- * disable API calls which do not use the built-in firmware or the firmware
- * cache when we know these calls will not work.
- *
- * The inner logic behind all this is a bit complex so it is worth summarizing
- * the kernel's own suspend/resume process with context and focus on how this
- * can impact the firmware API.
- *
- * First a review on how we go to suspend::
- *
- *	pm_suspend() --> enter_state() -->
- *	sys_sync()
- *	suspend_prepare() -->
- *		__pm_notifier_call_chain(PM_SUSPEND_PREPARE, ...);
- *		suspend_freeze_processes() -->
- *			freeze_processes() -->
- *				__usermodehelper_set_disable_depth(UMH_DISABLED);
- *				freeze all tasks ...
- *			freeze_kernel_threads()
- *	suspend_devices_and_enter() -->
- *		dpm_suspend_start() -->
- *				dpm_prepare()
- *				dpm_suspend()
- *		suspend_enter()  -->
- *			platform_suspend_prepare()
- *			dpm_suspend_late()
- *			freeze_enter()
- *			syscore_suspend()
- *
- * When we resume we bail out of a loop from suspend_devices_and_enter() and
- * unwind back out to the caller enter_state() where we were before as follows::
- *
- * 	enter_state() -->
- *	suspend_devices_and_enter() --> (bail from loop)
- *		dpm_resume_end() -->
- *			dpm_resume()
- *			dpm_complete()
- *	suspend_finish() -->
- *		suspend_thaw_processes() -->
- *			thaw_processes() -->
- *				__usermodehelper_set_disable_depth(UMH_FREEZING);
- *				thaw_workqueues();
- *				thaw all processes ...
- *				usermodehelper_enable();
- *		pm_notifier_call_chain(PM_POST_SUSPEND);
- *
- * fw_pm_notify() works through pm_notifier_call_chain().
- */
 static int fw_pm_notify(struct notifier_block *notify_block,
 			unsigned long mode, void *unused)
 {
···
 		 */
 		kill_pending_fw_fallback_reqs(true);
 		device_cache_fw_images();
-		disable_firmware();
 		break;
 
 	case PM_POST_SUSPEND:
···
 		mutex_lock(&fw_lock);
 		fw_cache.state = FW_LOADER_NO_CACHE;
 		mutex_unlock(&fw_lock);
-		enable_firmware();
 
 		device_uncache_fw_images_delay(10 * MSEC_PER_SEC);
 		break;
···
 static int fw_shutdown_notify(struct notifier_block *unused1,
 			      unsigned long unused2, void *unused3)
 {
-	disable_firmware();
 	/*
 	 * Kill all pending fallback requests to avoid both stalling shutdown,
 	 * and avoid a deadlock with the usermode_lock.
···
 
 static int __init firmware_class_init(void)
 {
-	enable_firmware();
 	fw_cache_init();
 	register_reboot_notifier(&fw_shutdown_nb);
 #ifdef CONFIG_FW_LOADER_USER_HELPER
···
 
 static void __exit firmware_class_exit(void)
 {
-	disable_firmware();
 #ifdef CONFIG_PM_SLEEP
 	unregister_syscore_ops(&fw_syscore_ops);
 	unregister_pm_notifier(&fw_cache.pm_notify);