Hi ulf, ? 2016/9/22 17:38, Ulf Hansson ??: > On 21 September 2016 at 03:43, Shawn Lin <shawn.lin at rock-chips.com> 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. > > So either the core has changed the clock rate by mistake at some other > execution path, or the host driver didn't set the correct clock rate > the first time when invoked via mmc_power_up()? > > Kind regards > Uffe > >> >> Reported-by: Xiao Yao <xiaoyao at rock-chips.com> >> Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com> >> --- >> >> drivers/mmc/core/mmc.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c >> index 3163bb9..989d37e 100644 >> --- a/drivers/mmc/core/mmc.c >> +++ b/drivers/mmc/core/mmc.c >> @@ -1282,6 +1282,8 @@ static int mmc_select_hs400es(struct mmc_card *card) >> if (err) >> goto out_err; >> >> + mmc_set_clock(host, card->ext_csd.hs_max_dtr); >> + >> err = mmc_switch_status(card); >> if (err) >> goto out_err; >> -- >> 2.3.7 >> >> > > > -- Best Regards Shawn Lin
