Re: [PATCH v2 1/3] mmc: dw_mmc: Using devm_clk_get_optional() for biu_clk

[Shawn Lin]

在 2026/02/13 星期五 11:08, 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.
>
> 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:
> [7:   binder:436_2: 4998] Unable to handle kernel paging request at virtual address fffffffffffffffe
> [7:   binder:436_2: 4998] Mem abort info:
> [7:   binder:436_2: 4998]   ESR = 0x0000000096000005
> [7:   binder:436_2: 4998]   EC = 0x25: DABT (current EL), IL = 32 bits
> [7:   binder:436_2: 4998]   SET = 0, FnV = 0
> [7:   binder:436_2: 4998]   EA = 0, S1PTW = 0
> [7:   binder:436_2: 4998]   FSC = 0x05: level 1 translation fault
> ...
> [7:   binder:436_2: 4998] Call trace:
> [7:   binder:436_2: 4998]  clk_prepare+0x10/0x24
> [7:   binder:436_2: 4998]  dw_mci_runtime_resume+0x50/0x2d8 [dw_mmc_samsung cd210e210975263404c28fc89778f369f8398f0c]
> [7:   binder:436_2: 4998]  dw_mci_exynos_runtime_resume+0x18/0x58 [dw_mmc_exynos_samsung 2735a594c7c9c9e8c65b0b87523fbf70dcaabfff]
> [7:   binder:436_2: 4998]  pm_generic_runtime_resume+0x40/0x58
> [7:   binder:436_2: 4998]  pm_runtime_force_resume+0x9c/0x134
> [7:   binder:436_2: 4998]  platform_pm_resume+0x40/0x8c
> [7:   binder:436_2: 4998]  dpm_run_callback+0x64/0x230
> [7:   binder:436_2: 4998]  __device_resume+0x1d8/0x394
> [7:   binder:436_2: 4998]  dpm_resume+0x110/0x2b8
> [7:   binder:436_2: 4998]  dpm_resume_end+0x1c/0x38
> [7:   binder:436_2: 4998]  suspend_devices_and_enter+0x828/0xab0
> [7:   binder:436_2: 4998]  pm_suspend+0x334/0x618
> [7:   binder:436_2: 4998]  state_store+0x104/0x144
> [7:   binder:436_2: 4998]  kobj_attr_store+0x30/0x48
> [7:   binder:436_2: 4998]  sysfs_kf_write+0x54/0x6c
> [7:   binder:436_2: 4998]  kernfs_fop_write_iter+0x104/0x1a8
> [7:   binder:436_2: 4998]  vfs_write+0x24c/0x2f4
> [7:   binder:436_2: 4998]  ksys_write+0x78/0xe8
> [7:   binder:436_2: 4998]  __arm64_sys_write+0x1c/0x2c
> [7:   binder:436_2: 4998]  invoke_syscall+0x58/0x114
> [7:   binder:436_2: 4998]  el0_svc_common+0xac/0xe0
> [7:   binder:436_2: 4998]  do_el0_svc+0x1c/0x28
> [7:   binder:436_2: 4998]  el0_svc+0x38/0x68
> [7:   binder:436_2: 4998]  el0t_64_sync_handler+0x68/0xbc
> [7:   binder:436_2: 4998]  el0t_64_sync+0x1a8/0x1ac

Acked-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>

> Signed-off-by: ping.gao <ping.gao@xxxxxxxxxxx>
> ---
>   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);