Re: [PATCH v7 8/8] scsi: ufs: Select INITIAL adapt for HS Gear4

[Can Guo]

On 2020-02-07 10:56, Can Guo wrote:
> On 2020-02-06 21:20, Avri Altman wrote:
> > Hi Can,
> >
> >
> > > ADAPT is added specifically for HS Gear4 mode only, select INITIAL 
> > > adapt
> > > before do power mode change to G4 and select no adapt before switch 
> > > to
> > > non-G4 modes.
> >
> > UFSHCI 3.0 says:
> > 7.4.1 Adapt
> > The use of Adapt isn't mandatory but the specification provides some
> > guidelines on its use.
> > The HCI should perform an Initial Adapt in the following cases if the
> > link is running at HS-G4
> > speed:
> >  - If DME_RESET is initiated.
> >  - If an unused line is activated for HS-G4.
> >  - If UECDME.EC is triggered with bit 3 set to '1'.
> >  - If a change between Rate A and Rate B in HS-G4 is performed.
> >
> > If it's not mandatory - why are we setting this for all vendors on all
> > platforms?
> > Or am I miss-reading the spec?
> >
> > Thanks,
> > Avri
>
> Hi Avri,
>
> Yes, it is not mandatory, but I don't know a flash vendor that
> refuses to use ADAPT so far, it is even recommended by flash vendors.
> So there is no meaning of adding a specific quirk for it, as all flash
> vendors need this quirk. Otherwise, we would need to add another vops
> to allow platform vendors to control it before send PMC.
>
> Any other suggestions?
>
> FYI, ADAPT sequence is used to train an M-RX equalizer. It gives both
> sides better signal integrity against the influence caused by
> temperature and voltage variations. ADAPT is also used by Quality of
> Service Monitoring for HS-G4.
>
> As for the usage of it, here is just setting the type of it before
> PMC to HS-G4, HW will use ADAPT, only if both sides support ADAPT,
> when it is required as what the spec is saying.
>
> Thanks,
>
> Can Guo.

Hi Avri,

I will drop this one for now as it may take some time to nail down it.
I will come back with a separate patch series for it later.

Thanks for the review.

Can Guo.