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

[Can Guo]

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.