linux-kernel - Re: [PATCH] drivers: clk: keystone: Fix parameter judgment in clk

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Message-ID: <CAPDyKFpX1+03w_Pa-Z2xRyHcft6nL4pgvKc5GuUbXfWXSk_MeQ@mail.gmail.com>
Date: Thu, 22 Jan 2026 18:56:51 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "ping.gao" <ping.gao@...sung.com>
Cc: jh80.chung@...sung.com, sebastian.reichel@...labora.com, 
	shawn.lin@...k-chips.com, linux-mmc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, hy50.seo@...sung.com, kwangwon.min@...sung.com
Subject: Re: [PATCH] drivers: clk: keystone: Fix parameter judgment in clk_prepare

On Wed, 21 Jan 2026 at 08:00, ping.gao <ping.gao@...sung.com> wrote:
>
>     The clk may return NULL or an ERR_PTR. Don't
>     treat an ERR_PTR as valid.
>
>     for example: biu_clk in dwmmc driver request 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@...sung.com>
> ---
>  drivers/clk/clk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 85d2f2481acf..6d62f69323b5 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1171,7 +1171,7 @@ static int clk_core_prepare_lock(struct clk_core *core)
>   */
>  int clk_prepare(struct clk *clk)
>  {
> -       if (!clk)
> +       if (IS_ERR_OR_NULL(clk))
>                 return 0;
>
>         return clk_core_prepare_lock(clk->core);
> --
> 2.50.1
>

This isn't the solution [1] that we discussed to solve the problem.
Please re-work the code in drivers/mmc/host/dw_mmc.c to use
devm_clk_get_optional() instead.

Moreover, please carefully read
Documentation/process/submitting-patches.rst, before you post anything
again.

Kind regards
Uffe

[1]
https://lore.kernel.org/all/aVp5IMvHKR8CtqSz@venus/