Re: [PATCH v11 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling

From: Stanley Chu
Date: Wed Jan 20 2021 - 08:19:11 EST

On Wed, 2021-01-20 at 02:04 -0800, Can Guo wrote:
> In contexts like suspend, shutdown and error handling, we need to suspend
> devfreq to make sure these contexts won't be disturbed by clock scaling.
> However, suspending devfreq is not enough since users can still trigger a
> clock scaling by manipulating the devfreq sysfs nodes like min/max_freq and
> governor even after devfreq is suspended. Moreover, mere suspending devfreq
> cannot synchroinze a clock scaling which has already been invoked through
> these sysfs nodes. Add one more flag in struct clk_scaling and wrap the
> entire func ufshcd_devfreq_scale() with the clk_scaling_lock, so that we
> can use this flag and clk_scaling_lock to control and synchronize clock
> scaling invoked through devfreq sysfs nodes.
> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>

Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>