Hi Stanley,
On Wed, Mar 29, 2023 at 04:39:30PM +0800, Stanley Chu wrote:
> Hi Adrien,
>
> On Sat, Feb 18, 2023 at 3:50 AM Adrien Thierry <athierry@xxxxxxxxxx> wrote:
> >
> > 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));
>
> Here, hba->pwr_info is not initialized yet, so
> hba->clk_scaling.saved_pwr_info will also have uninitialized values.
> This is logically incorrect.
>
> First of all, hba->saved_pwr_info is originally designed to keep the
> "scaled-up" gear. This statement breaks it.
>
> In addition, the incorrect hba->save_pwr_info may cause serious issues
> in ufshcd_scale_gear(), as power mode changes will fail due to
> incorrect "new_pwr_info".
>
> Could you please revert this patch first and then upload a fixed one?
Thanks for pointing that out.
I also realized today that the patch introduces a devfreq warning:
"devfreq 1d84000.ufs: Couldn't update frequency transition information".
So I'm going to post a revert and take the time to come up with an
improved solution that fixes both issues.
Best,
Adrien
