linux-kernel - Re: [PATCH] MMC:dw_mmc:when enable biu_clk should check whether this clk is normal

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Message-ID: <b30a4977-7202-4771-8977-ff03e8453d16@rock-chips.com>
Date: Sun, 4 Jan 2026 10:55:48 +0800
From: Shawn Lin <shawn.lin@...k-chips.com>
To: "ping.gao" <ping.gao@...sung.com>
Cc: shawn.lin@...k-chips.com, jh80.chung@...sung.com, ulf.hansson@...aro.org,
 linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: Re: [PATCH] MMC:dw_mmc:when enable biu_clk should check whether this
 clk is normal

在 2026/01/04 星期日 10:38, ping.gao 写道:
> some vendor doesn't use biu_clk , enable it will panic
> log is below:

I still don't understand the real issue you tried to solve.

host->biu_clk is got via devm_clk_get() in dw_mci_probe(). If
succeed, immediately it's enabled a few lines below. Otherwise,
dw_mci_probe() returns with failure. Seems you are not enabling it in
runtime callbacks, but why clk_prepare_enable(host->biu_clk) is able
to work when driver probed?


> [  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/mmc/host/dw_mmc.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index c5db92bbb094..61f6986f15ef 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -3633,9 +3633,15 @@ int dw_mci_runtime_resume(struct device *dev)
>   	if (host->slot &&
>   	    (mmc_host_can_gpio_cd(host->slot->mmc) ||
>   	     !mmc_card_is_removable(host->slot->mmc))) {
> -		ret = clk_prepare_enable(host->biu_clk);
> -		if (ret)
> -			return ret;
> +		if (IS_ERR(host->biu_clk)) {
> +			dev_dbg(host->dev, "biu clock not available\n");
> +		} else {
> +			ret = clk_prepare_enable(host->biu_clk);
> +			if (ret) {
> +				dev_err(host->dev, "failed to enable biu clock\n");
> +				goto err;
> +			}
> +		}
>   	}
>   
>   	ret = clk_prepare_enable(host->ciu_clk);