This is a note to let you know that I've just added the patch titled
scsi: ufs: core: Initialize devfreq synchronously
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-ufs-core-initialize-devfreq-synchronously.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 937e1b69386ea5c3faa8006bdaf94d023014f45e
Author: Adrien Thierry <athierry@xxxxxxxxxx>
Date: Fri Feb 17 14:44:22 2023 -0500
scsi: ufs: core: Initialize devfreq synchronously
[ Upstream commit 7dafc3e007918384c8693ff8d70381b5c1e9c247 ]
During UFS initialization, devfreq initialization is 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
built 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.
*/
Such a deadlock was experienced on the Qualcomm QDrive3/sa8540p-ride. With
DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning.
Fix both the warning and the deadlock by moving devfreq initialization out
of the async routine.
Tested on the sa8540p-ride by using fio to put the UFS under load, and
printing the trace generated by
/sys/kernel/tracing/events/ufs/ufshcd_clk_scaling events. The trace looks
similar with and without the change.
Link: https://lore.kernel.org/r/20230217194423.42553-1-athierry@xxxxxxxxxx
Signed-off-by: Adrien Thierry <athierry@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 120831428ec6f..eaa91aec036b1 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1307,6 +1307,13 @@ static int ufshcd_devfreq_target(struct device *dev,
struct ufs_clk_info *clki;
unsigned long irq_flags;
+ /*
+ * Skip devfreq if UFS initialization is not finished.
+ * Otherwise ufs could be in a inconsistent state.
+ */
+ if (!smp_load_acquire(&hba->logical_unit_scan_finished))
+ return 0;
+
if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;
@@ -7881,22 +7888,6 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
if (ret)
goto out;
- /* Initialize devfreq after UFS device is detected */
- if (ufshcd_is_clkscaling_supported(hba)) {
- memcpy(&hba->clk_scaling.saved_pwr_info.info,
- &hba->pwr_info,
- sizeof(struct ufs_pa_layer_attr));
- hba->clk_scaling.saved_pwr_info.is_valid = true;
- hba->clk_scaling.is_allowed = true;
-
- ret = ufshcd_devfreq_init(hba);
- if (ret)
- goto out;
-
- hba->clk_scaling.is_enabled = true;
- ufshcd_init_clk_scaling_sysfs(hba);
- }
-
ufs_bsg_probe(hba);
ufshpb_init(hba);
scsi_scan_host(hba->host);
@@ -8030,6 +8021,12 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
if (ret) {
pm_runtime_put_sync(hba->dev);
ufshcd_hba_exit(hba);
+ } else {
+ /*
+ * Make sure that when reader code sees UFS initialization has finished,
+ * all initialization steps have really been executed.
+ */
+ smp_store_release(&hba->logical_unit_scan_finished, true);
}
}
@@ -9590,12 +9587,30 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
*/
ufshcd_set_ufs_dev_active(hba);
+ /* Initialize devfreq */
+ if (ufshcd_is_clkscaling_supported(hba)) {
+ memcpy(&hba->clk_scaling.saved_pwr_info.info,
+ &hba->pwr_info,
+ sizeof(struct ufs_pa_layer_attr));
+ hba->clk_scaling.saved_pwr_info.is_valid = true;
+ hba->clk_scaling.is_allowed = true;
+
+ err = ufshcd_devfreq_init(hba);
+ if (err)
+ goto rpm_put_sync;
+
+ hba->clk_scaling.is_enabled = true;
+ ufshcd_init_clk_scaling_sysfs(hba);
+ }
+
async_schedule(ufshcd_async_scan, hba);
ufs_sysfs_add_nodes(hba->dev);
device_enable_async_suspend(dev);
return 0;
+rpm_put_sync:
+ pm_runtime_put_sync(dev);
free_tmf_queue:
blk_cleanup_queue(hba->tmf_queue);
free_tmf_tag_set:
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index c8513cc6c2bdd..33d9c096ec7fd 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -838,6 +838,7 @@ struct ufs_hba {
struct completion *uic_async_done;
enum ufshcd_state ufshcd_state;
+ bool logical_unit_scan_finished;
u32 eh_flags;
u32 intr_mask;
u16 ee_ctrl_mask; /* Exception event mask */
