Re: [PATCH v3] scsi: ufs: Allow RTT negotiation

[Bart Van Assche]

On 5/14/24 14:34, Avri Altman wrote:
> > On 5/13/24 23:08, Avri Altman wrote:
> > > +/* bMaxNumOfRTT is equal to two after device manufacturing */
> > > +#define DEFAULT_MAX_NUM_RTT 2
> > > [ ... ]
> > > +     /* do not override if it was already written */
> > > +     if (dev_rtt != DEFAULT_MAX_NUM_RTT)
> > > +             return;
> >
> > I haven't found any text in the UFSHCI 4.0 specification that says
> > that the default value for the number of outstanding RTT requests
> > should be 2. Did I perhaps overlook something? If I didn't overlook
> > anything, the driver should not try to check whether dev_rtt is at its
> > default value.
> JEDEC Standard No. 220F Page 150 Line 2837 says: "bMaxNumOfRTT is equal to two after device manufacturing,"

Thanks Avri for having looked this up.

My understanding is that the above check won't work as intended if
ufshcd_rtt_set() does not modify the RTT value. Wouldn't it be better
to add a boolean in struct ufs_hba that indicates whether or not
ufshcd_rtt_set() has been called before?

Thanks,

Bart.