Re: [PATCH v1] scsi: ufs: remove clk_scaling_lock when clkscaling isn't supported.

[Bart Van Assche]

On 2/4/22 23:39, Kiwoong Kim wrote:
> clk_scaling_lock is to prevent from running clkscaling related operations
> with others which might be affected by the operations concurrently.
> I think it looks hardware specific.
> If the feature isn't supported, I think there is no reasonto prevent from
> running other functions, such as ufshcd_queuecommand and
> ufshcd_exec_dev_cmd, concurrently.
>
> So I add a condition at some points protecting with clk_scaling_lock.
>
> Signed-off-by: Kiwoong Kim <kwmad.kim@xxxxxxxxxxx>
> ---
>   drivers/scsi/ufs/ufshcd.c | 21 ++++++++++++++-------
>   1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 460d2b4..8471c90 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2980,7 +2980,8 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
>   	/* Protects use of hba->reserved_slot. */
>   	lockdep_assert_held(&hba->dev_cmd.lock);
>   
> -	down_read(&hba->clk_scaling_lock);
> +	if (ufshcd_is_clkscaling_supported(hba))
> +		down_read(&hba->clk_scaling_lock);
>   
>   	lrbp = &hba->lrb[tag];
>   	WARN_ON(lrbp->cmd);

I don't like this patch at all. This patch makes testing the UFS driver 
more complicated without having any clear benefit. Additionally, adding 
if-statements in front of locking makes static source code analysis 
harder and is an anti-pattern. Please don't do this.

Bart.