On 22 September 2016 at 12:06, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote: > Hi ulf, > > 在 2016/9/22 17:38, Ulf Hansson 写道: >> >> 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? Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
