[PATCH] scsi: ufs: probe hba and add lus synchronously

[Adrien Thierry <athierry@redhat.com>]

During ufs initialization, hba and lus probing are asynchronous.
ufshcd_async_scan() calls ufshcd_add_lus(), which in turn initializes
devfreq for ufs. The simple ondemand governor is then loaded. If it is
build as a module, request_module() is called and throws a warning:

WARNING: CPU: 7 PID: 167 at kernel/kmod.c:136 __request_module+0x1e0/0x460
Modules linked in: crct10dif_ce llcc_qcom phy_qcom_qmp_usb ufs_qcom phy_qcom_snps_femto_v2 ufshcd_pltfrm phy_qcom_qmp_combo ufshcd_core phy_qcom_qmp_ufs qcom_wdt socinfo fuse ipv6
CPU: 7 PID: 167 Comm: kworker/u16:3 Not tainted 6.2.0-rc6-00009-g58706f7fb045 #1
Hardware name: Qualcomm SA8540P Ride (DT)
Workqueue: events_unbound async_run_entry_fn
pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __request_module+0x1e0/0x460
lr : __request_module+0x1d8/0x460
sp : ffff800009323b90
x29: ffff800009323b90 x28: 0000000000000000 x27: 0000000000000000
x26: ffff800009323d50 x25: ffff7b9045f57810 x24: ffff7b9045f57830
x23: ffffdc5a83e426e8 x22: ffffdc5ae80a9818 x21: 0000000000000001
x20: ffffdc5ae7502f98 x19: ffff7b9045f57800 x18: ffffffffffffffff
x17: 312f716572667665 x16: 642f7366752e3030 x15: 0000000000000000
x14: 000000000000021c x13: 0000000000005400 x12: ffff7b9042ed7614
x11: ffff7b9042ed7600 x10: 00000000636c0890 x9 : 0000000000000038
x8 : ffff7b9045f2c880 x7 : ffff7b9045f57c68 x6 : 0000000000000080
x5 : 0000000000000000 x4 : 8000000000000000 x3 : 0000000000000000
x2 : 0000000000000000 x1 : ffffdc5ae5d382f0 x0 : 0000000000000001
Call trace:
 __request_module+0x1e0/0x460
 try_then_request_governor+0x7c/0x100
 devfreq_add_device+0x4b0/0x5fc
 ufshcd_async_scan+0x1d4/0x310 [ufshcd_core]
 async_run_entry_fn+0x34/0xe0
 process_one_work+0x1d0/0x320
 worker_thread+0x14c/0x444
 kthread+0x10c/0x110
 ret_from_fork+0x10/0x20

This occurs because synchronous module loading from async is not
allowed. According to __request_module():

/*
 * We don't allow synchronous module loading from async.  Module
 * init may invoke async_synchronize_full() which will end up
 * waiting for this task which already is waiting for the module
 * loading to complete, leading to a deadlock.
 */

I experienced such a deadlock on the Qualcomm QDrive3/sa8540p-ride. With
DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning.

This patch fixes both the warning and the deadlock, by probing hba and
lus synchronously during ufs initialization.

Signed-off-by: Adrien Thierry <athierry@redhat.com>
---
 drivers/ufs/core/ufshcd.c | 44 +++++++++++----------------------------
 1 file changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 3a1c4d31e010..2cf8e09b1a9d 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -245,7 +245,6 @@ static const struct ufs_dev_quirk ufs_fixups[] = {
 };
 
 static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba);
-static void ufshcd_async_scan(void *data, async_cookie_t cookie);
 static int ufshcd_reset_and_restore(struct ufs_hba *hba);
 static int ufshcd_eh_host_reset_handler(struct scsi_cmnd *cmd);
 static int ufshcd_clear_tm_cmd(struct ufs_hba *hba, int tag);
@@ -8263,36 +8262,6 @@ static int ufshcd_probe_hba(struct ufs_hba *hba, bool init_dev_params)
 	return ret;
 }
 
-/**
- * ufshcd_async_scan - asynchronous execution for probing hba
- * @data: data pointer to pass to this function
- * @cookie: cookie data
- */
-static void ufshcd_async_scan(void *data, async_cookie_t cookie)
-{
-	struct ufs_hba *hba = (struct ufs_hba *)data;
-	int ret;
-
-	down(&hba->host_sem);
-	/* Initialize hba, detect and initialize UFS device */
-	ret = ufshcd_probe_hba(hba, true);
-	up(&hba->host_sem);
-	if (ret)
-		goto out;
-
-	/* Probe and add UFS logical units  */
-	ret = ufshcd_add_lus(hba);
-out:
-	/*
-	 * If we failed to initialize the device or the device is not
-	 * present, turn off the power/clocks etc.
-	 */
-	if (ret) {
-		pm_runtime_put_sync(hba->dev);
-		ufshcd_hba_exit(hba);
-	}
-}
-
 static enum scsi_timeout_action ufshcd_eh_timed_out(struct scsi_cmnd *scmd)
 {
 	struct ufs_hba *hba = shost_priv(scmd->device->host);
@@ -9896,12 +9865,23 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	 */
 	ufshcd_set_ufs_dev_active(hba);
 
-	async_schedule(ufshcd_async_scan, hba);
+	/* Initialize hba, detect and initialize UFS device */
+	err = ufshcd_probe_hba(hba, true);
+	if (err)
+		goto out_power_off;
+
+	/* Probe and add UFS logical units  */
+	err = ufshcd_add_lus(hba);
+	if (err)
+		goto out_power_off;
+
 	ufs_sysfs_add_nodes(hba->dev);
 
 	device_enable_async_suspend(dev);
 	return 0;
 
+out_power_off:
+	pm_runtime_put_sync(hba->dev);
 free_tmf_queue:
 	blk_mq_destroy_queue(hba->tmf_queue);
 	blk_put_queue(hba->tmf_queue);
-- 
2.39.1