Re: [PATCH 3/5] mmc: core: changes frequency to hs_max_dtr when selecting hs400es

[Shawn Lin]

On 2016/9/22 18:21, Ulf Hansson wrote:
> On 22 September 2016 at 12:06, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
> > Hi ulf,
> >
> > å 2016/9/22 17:38, Ulf Hansson åé:
> > > On 21 September 2016 at 03:43, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
> > > > Per JESD84-B51 P69, Host need to change frequency to <=52MHz after
> > > > setting HS_TIMING to 0x1, and host may changes frequency to <= 200MHz
> > > > after setting HS_TIMING to 0x3. It seems there is no difference if
> > > > we don't change frequency to <= 52MHz as f_init is already less than
> > > > 52MHz. But actually it does make difference. When doing compatibility
> > > > test we see failures for some eMMC devices without changing the
> > > > frequency to hs_max_dtr. And let's read the spec again, we could see
> > > > that "Host may changes frequency to 200MHz" implies that it's not
> > > > mandatory. But the "Host need to change frequency to <= 52MHz" implies
> > > > that we should do this.
> > >
> > >
> > > I don't get this. Are you saying that f_init > 52 MHz? That should not
> > > be impossible, right!?
> >
> >
> > nope, I was saying that the spec implies we to set clock after
> > setting HS_TIMING to 0x1 when doing hs400es selection.
> >
> > I thought there is no difference because the spec says "Host need to
> > change frequency to <= 52MHz", and the f_init(<=400k) is <= 52MHz,
> > right? So I didn't set clock to hs_max_dtr. But I think I misunderstood
> > the spec, so this patch will fix this.
>
> Okay, I see what you mean now!
>
> In other words:
> The card expects the clock rate to increase from the current used
> f_init (which is <= 400KHz), but still being <= 52MHz, when you have
> set HS_TIMING to 0x1.
>
> Okay, we can do that change! Could you try to improve the change log a
> little bit or you want me to help?

yep, I could change the commit msg a bit and fix another
copy-paste error, then respin v2.
BTW, I noticed you have applied one of these 5 patches, so
I will remove that one for V2.

Thanks, Ulf.

> Kind regards
> Uffe


--
Best Regards
Shawn Lin