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

[Stanley Chu]

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