Re: [PATCH v1 1/2] scsi: ufs: add required delay after gating reference clock

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Hi Stanely,

On 2020-02-17 21:42, Can Guo wrote:
On 2020-02-17 21:34, Stanley Chu wrote:
Hi Can,

On Mon, 2020-02-17 at 21:22 +0800, Can Guo wrote:
On 2020-02-17 21:12, Stanley Chu wrote:
> Hi Can,
>
>
>> >  			} else if (!on && clki->enabled) {
>> >  				clk_disable_unprepare(clki->clk);
>> > +				wait_us = hba->dev_info.clk_gating_wait_us;
>> > +				if (ref_clk && wait_us)
>> > +					usleep_range(wait_us, wait_us + 10);
>>
>> Hi St,anley,
>>
>> If wait_us is 1us, it would be inappropriate to use usleep_range()
>> here.
>> You have checks of the delay in patch #2, but why it is not needed
>> here?
>>
>> Thanks,
>> Can Guo.
>
> You are right. I could make that delay checking as common function so
> it
> can be used here as well to cover all possible values.
>
> Thanks for suggestion.
> Stanley

Hi Stanley,

One more thing, as in patch #2, you have already added delays in your
ufshcd_vops_setup_clocks(OFF, PRE_CHANGE) path, plus this delay here,
don't you delay for 2*bRefClkGatingWaitTime in ufshcd_setup_clocks()?
As the delay added in your vops also delays the actions of turning
off all the other clocks in ufshcd_setup_clocks(), you don't need the
delay here again, do you agree?

MediaTek driver is not using reference clocks named as "ref_clk" defined
in device tree, thus the delay specific for "ref_clk" in
ufshcd_setup_clocks() will not be applied in MediaTek platform.

This patch is aimed to add delay for this kind of "ref_clk" used by any
future vendors.

Anyway thanks for the reminding : )


Thanks,
Can Guo.


Thanks,
Stanley

Hi Stanley,

Then we are unluckily hit by this change. We have ref_clk in DT, thus
this change would add unwanted delays to our platforms. but still we
disable device's ref_clk in vops. :)

Could you please hold on patch #1 first? I need sometime to have a
dicussion with my colleagues on this.

Thanks.
Can Guo.

Since we all need this delay here, how about put the delay in the
entrence of ufshcd_setup_clocks(), before vops_setup_clocks()?
If so, we can remove all the delays we added in our vops since the
delay anyways delays everything inside ufshcd_setup_clocks().

Meanwhile, if you want to modify the delay
(hba->dev_info.clk_gating_wait_us) for some reasons, say for specific
UFS devices, you still can do it in vops_apply_dev_quirks().

What do you say?

Thanks,
Can Guo.



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