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.
*/
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 moving devfreq
initialization out of the async routine.
I tested this 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.
Signed-off-by: Adrien Thierry <athierry@xxxxxxxxxx>
---
v3: Addressed Bart's comments
v2: Addressed Bart's comments
drivers/ufs/core/ufshcd.c | 47 ++++++++++++++++++++++++++-------------
include/ufs/ufshcd.h | 1 +
2 files changed, 32 insertions(+), 16 deletions(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 3a1c4d31e010..2c22a1367440 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1357,6 +1357,13 @@ 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;
@@ -8136,22 +8143,6 @@ 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);
@@ -8290,6 +8281,12 @@ 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);
}
}
@@ -9896,12 +9893,30 @@ 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_mq_destroy_queue(hba->tmf_queue);
blk_put_queue(hba->tmf_queue);
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 727084cd79be..941ede501367 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -896,6 +896,7 @@ 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;
--
2.39.1
