Re: [PATCH] drivers: dw_mmc: Replace devm_clk_get with devm_clk_get_optional

[Shawn Lin <shawn.lin@rock-chips.com>]

Hi Ping Gao

在 2026/01/23 星期五 16:56, ping.gao 写道:
> 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.
> 

Sorry for not noticing this patch as the versioning problem.

You should improve the commit title to match the convention like:
mmc: dw_mmc: Using devm_clk_get_optional() for biu_clk

> 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
> ...

The​ timestamp could be trimmed.

> [  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@samsung.com>
> ---
>   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");

You change biu_clk to optional, so you need to update
Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.yaml
because minItems says 2 there.

And you also change the behaviour of drivers/mmc/host/dw_mmc-k3.c
which tries to set/get biu_clk and setup cards, it's apparently rely on
dw_mmc core to make biu_clk a must one.

So I suggest you at least need a extra 3rd patch to help dw_mmc-k3
identify missing biu_clk case.

For the next submission, please order the patchset as
1. synopsys-dw-mshc.yaml change
2. dw_mmc-k3 change
3. dw_mmc.c change

>   	if (IS_ERR(host->biu_clk)) {
>   		dev_dbg(host->dev, "biu clock not available\n");
>   		ret = PTR_ERR(host->biu_clk);
>