Re: [PATCH v2 4/4] scsi: ufs: core: Report the current clock frequency to devfreq

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Lockless read of shared frequency states (target_freq and curr_freq) introduces a data race.
--

commit 33056f7bc209eb72a0cfba73ae939b67d7a4ed81
Author: Bean Huo <beanhuo@micron.com>

scsi: ufs: core: Report the current clock frequency to devfreq

When a driver does not provide a ->get_cur_freq() callback, the cur_freq
sysfs attribute shows devfreq->previous_freq. This commit adds a
->get_cur_freq() callback to report the current clock frequency accurately.

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 351c76094b9ff..bac95e891de5d 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1711,6 +1711,26 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
>  	return 0;
>  }
>  
> +static int ufshcd_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
> +{
> +	struct ufs_hba *hba = dev_get_drvdata(dev);
> +
> +	if (!ufshcd_is_clkscaling_supported(hba))
> +		return -EINVAL;
> +
> +	if (hba->use_pm_opp) {
> +		*freq = hba->clk_scaling.target_freq;

[Severity: Low]
Is it possible for this lockless read of target_freq to race with frequency
scaling updates?

If the devfreq sysfs cur_freq attribute is read concurrently with updates like
ufshcd_clkscale_enable_store() or ufshcd_devfreq_target(), could it trigger a
KCSAN data race warning or result in a stale read? Should this be protected or
use READ_ONCE()?

> +	} else {
> +		struct ufs_clk_info *clki;
> +
> +		clki = list_first_entry(&hba->clk_list_head,
> +					struct ufs_clk_info, list);
> +		*freq = clki->curr_freq;

[Severity: Low]
Similarly, could this lockless read of curr_freq race with updates in the same
way? Might READ_ONCE() be needed here to formally resolve the race?

> +	}
> +
> +	return 0;
> +}
> +
>  static int ufshcd_devfreq_init(struct ufs_hba *hba)
>  {
>  	struct list_head *clk_list = &hba->clk_list_head;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260907192140.2701755-1-beanhuo@iokpp.de?part=4