From: Adrien Thierry <athierry@xxxxxxxxxx> [ 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> --- drivers/scsi/ufs/ufshcd.c | 47 ++++++++++++++++++++++++++------------- drivers/scsi/ufs/ufshcd.h | 1 + 2 files changed, 32 insertions(+), 16 deletions(-) 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 */ -- 2.39.2
