Re: [PATCH] rtc: spear: check return value of clk_enable in resume

[Alexandre Belloni]

On 01/03/2026 16:19:58+0000, Zhaoyang Yu wrote:
> In spear_rtc_resume(), the return value of clk_enable() is currently
> ignored. If clk_enable() fails, the driver proceeds to call
> spear_rtc_enable_interrupt().
> 
> The spear_rtc_enable_interrupt() function performs a readl() on the
> RTC control register (CTRL_REG) as its first operation. Accessing an
> MMIO register of a peripheral without an enabled functional clock is
> unsafe on SPEAr architectures and can lead to a system hang or data
> abort.
> 
> Fix this by checking the return value of clk_enable(). If it fails,
> print an error message and return the error code to avoid the unsafe
> register access.
> 
> Signed-off-by: Zhaoyang Yu <2426767509@xxxxxx>
> ---
>  drivers/rtc/rtc-spear.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-spear.c b/drivers/rtc/rtc-spear.c
> index 959acff8faff..9bf7cf264715 100644
> --- a/drivers/rtc/rtc-spear.c
> +++ b/drivers/rtc/rtc-spear.c
> @@ -437,7 +437,7 @@ static int spear_rtc_resume(struct device *dev)
>  {
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct spear_rtc_config *config = platform_get_drvdata(pdev);
> -	int irq;
> +	int irq, ret;
>  
>  	irq = platform_get_irq(pdev, 0);
>  
> @@ -447,7 +447,11 @@ static int spear_rtc_resume(struct device *dev)
>  			config->irq_wake = 0;
>  		}
>  	} else {
> -		clk_enable(config->clk);

On spear, this function will never fail as this ultimately calls static
void clk_gate_endisable.

> +		ret = clk_enable(config->clk);
> +		if (ret) {
> +			dev_err(dev, "Unable to enable clock on resume: %d\n", ret);
> +			return ret;
> +		}
>  		spear_rtc_enable_interrupt(config);
>  	}
>  
> -- 
> 2.34.1
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com