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@samsung.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

Quoting ping.gao (2026-01-22 18:33:58)
> 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

[...]

> 
> 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))

Don't pass an error pointer to this function. You should have checked
that when getting the clk with something like clk_get().