Re: [PATCH] drivers: dw_mmc: Replace devm_clk_get with devm_clk_get_optional
From: ping.gao
Date: Wed Feb 11 2026 - 03:13:41 EST
On Fri, 23 Jan 2026 10:46:45, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > On Fri, 23 Jan 2026 at 09:51, ping.gao <ping.gao@xxxxxxxxxxx> wrote:
> >
> > By using devm_clk_get_optional, if clk is optional for device and not define in dts
> > it will return NULL, then clk_prepare_enable/clk_disable_unprepare for biu_clk is safe to
> > bail out internally.
> >
> > before biu_clk in dwmmc driver devm_clk_get fail, but it's ERR_PTR,
> > not null,it will panic when call clk_prepare
> > log is below:
> > [ 438.400868] [7: binder:436_2: 4998] Unable to handle kernel paging request at virtual address fffffffffffffffe
> > [ 438.400877] [7: binder:436_2: 4998] Mem abort info:
> > [ 438.400881] [7: binder:436_2: 4998] ESR = 0x0000000096000005
> > [ 438.400887] [7: binder:436_2: 4998] EC = 0x25: DABT (current EL), IL = 32 bits
> > [ 438.400894] [7: binder:436_2: 4998] SET = 0, FnV = 0
> > [ 438.400899] [7: binder:436_2: 4998] EA = 0, S1PTW = 0
> > [ 438.400904] [7: binder:436_2: 4998] FSC = 0x05: level 1 translation fault
> > ...
> > [ 438.409424] [7: binder:436_2: 4998] Call trace:
> > [ 438.409429] [7: binder:436_2: 4998] clk_prepare+0x10/0x24
> > [ 438.409439] [7: binder:436_2: 4998] dw_mci_runtime_resume+0x50/0x2d8 [dw_mmc_samsung cd210e210975263404c28fc89778f369f8398f0c]
> > [ 438.409471] [7: binder:436_2: 4998] dw_mci_exynos_runtime_resume+0x18/0x58 [dw_mmc_exynos_samsung 2735a594c7c9c9e8c65b0b87523fbf70dcaabfff]
> > [ 438.409496] [7: binder:436_2: 4998] pm_generic_runtime_resume+0x40/0x58
> > [ 438.409506] [7: binder:436_2: 4998] pm_runtime_force_resume+0x9c/0x134
> > [ 438.409517] [7: binder:436_2: 4998] platform_pm_resume+0x40/0x8c
> > [ 438.409529] [7: binder:436_2: 4998] dpm_run_callback+0x64/0x230
> > [ 438.409540] [7: binder:436_2: 4998] __device_resume+0x1d8/0x394
> > [ 438.409551] [7: binder:436_2: 4998] dpm_resume+0x110/0x2b8
> > [ 438.409561] [7: binder:436_2: 4998] dpm_resume_end+0x1c/0x38
> > [ 438.409570] [7: binder:436_2: 4998] suspend_devices_and_enter+0x828/0xab0
> > [ 438.409582] [7: binder:436_2: 4998] pm_suspend+0x334/0x618
> > [ 438.409592] [7: binder:436_2: 4998] state_store+0x104/0x144
> > [ 438.409601] [7: binder:436_2: 4998] kobj_attr_store+0x30/0x48
> > [ 438.409610] [7: binder:436_2: 4998] sysfs_kf_write+0x54/0x6c
> > [ 438.409619] [7: binder:436_2: 4998] kernfs_fop_write_iter+0x104/0x1a8
> > [ 438.409628] [7: binder:436_2: 4998] vfs_write+0x24c/0x2f4
> > [ 438.409640] [7: binder:436_2: 4998] ksys_write+0x78/0xe8
> > [ 438.409652] [7: binder:436_2: 4998] __arm64_sys_write+0x1c/0x2c
> > [ 438.409664] [7: binder:436_2: 4998] invoke_syscall+0x58/0x114
> > [ 438.409676] [7: binder:436_2: 4998] el0_svc_common+0xac/0xe0
> > [ 438.409687] [7: binder:436_2: 4998] do_el0_svc+0x1c/0x28
> > [ 438.409698] [7: binder:436_2: 4998] el0_svc+0x38/0x68
> > [ 438.409705] [7: binder:436_2: 4998] el0t_64_sync_handler+0x68/0xbc
> > [ 438.409712] [7: binder:436_2: 4998] el0t_64_sync+0x1a8/0x1ac
> >
> > Signed-off-by: ping.gao <ping.gao@xxxxxxxxxxx>
>
> You are not versioning your patches, which makes it difficult for me
> to manage them. Again, please read
> Documentation/process/submitting-patches.rst before you continue to
> post any more patches.
>
> Anyway, I can pick this up as is for now, when Shawn has reviewed it.
>
> Kind regards
> Uffe
Hi, Shawn:
could you please review this patch?
best regards
Gaoping
> > ---
> > drivers/mmc/host/dw_mmc.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index c5db92bbb094..6bcc1e7233c0 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -3375,7 +3375,7 @@ int dw_mci_probe(struct dw_mci *host)
> > "platform data not available\n");
> > }
> >
> > - host->biu_clk = devm_clk_get(host->dev, "biu");
> > + host->biu_clk = devm_clk_get_optional(host->dev, "biu");
> > if (IS_ERR(host->biu_clk)) {
> > dev_dbg(host->dev, "biu clock not available\n");
> > ret = PTR_ERR(host->biu_clk);
> > --
> > 2.50.1
> >