Re: [PATCH v4] scsi: ufs: core: Don't perform UFS clkscale if host asyn scan in progress

[Ziqi Chen <quic_ziqichen@quicinc.com>]

On 7/30/2025 11:50 PM, Bart Van Assche wrote:
> On 7/30/25 5:55 AM, Peter Wang (王信友) wrote:
>> Another idea is to only start ufshcd_devfreq_init
>> when shost->async_scan = 0.
> 
> Hmm ... I don't think that this is a solution. There are multiple
> ways for triggering a LUN scan and my understanding is that the
> clock scaling code should be serialized against LUN scanning.
> 
> Here is an example of how LUN scanning can be triggered from user
> space by writing into the 'scan' sysfs attribute, even if
> shost->async_scan = 0:
> 
> echo "- - -" > /sys/class/scsi_host/host.../scan
> 
> Bart.

Hi  Peter && Bart,

How do you think about using

if (!mutex_trylock(&hba->host->scan_mutex))
	return -EAGAIN;

instead of

mutex_lock(&hba->host->scan_mutex);

But this way will cause one line print of devfreq failed.

BRs
Ziqi