[PATCH v1 02/10] ufs: host: mediatek: Correct clock scaling with PM QoS flow

[Peter Wang (王信友)]

On Fri, 2025-09-19 at 14:02 -0700, Bart Van Assche wrote:
> 
> Hmm ... it is not clear to me why this change is specific to MediaTek
> host controllers. Please move the code changes in this patch from the
> MediaTek driver into the UFSHCI driver core.
> 
> Additionally, why is this change necessary? Suspend and resume should
> happen quickly. Does removing CPU latency QoS requests during suspend
> and resume really save power? Has the power impact of this patch been
> measured?
> 
> Thanks,
> 
> Bart.


Hi Bart,

No, it does not affect power, it affects performance after resume.
After suspend, the UFS core always releases pm_qos, so power is not a
concern.
https://elixir.bootlin.com/linux/v6.16.8/source/drivers/ufs/core/ufshcd.c#L10169

However, after resume, pm_qos is not re-acquired if it was released
during the previous suspend. Therefore, if we set the gear to a high 
value for performance, this could be impacted. But in the UFS core,
the gear should be set to low during suspend, so there is no need to 
re-acquire pm_qos after resume.

Thansk.
Peter