> -----Original Message----- > From: Marek Vasut [mailto:marek.va...@gmail.com] > Sent: 2019年3月18日 19:53 > To: BOUGH CHEN <haibo.c...@nxp.com>; jh80.ch...@samsung.com; > tr...@konsulko.com > Cc: marek.vasut+rene...@gmail.com; Ye Li <ye...@nxp.com>; dl-uboot-imx > <uboot-...@nxp.com>; u-boot@lists.denx.de > Subject: Re: [PATCH] mmc: correct the HS400 initialization process > > On 3/18/19 9:23 AM, BOUGH CHEN wrote: > > After the commit b9a2a0e2e9c0 ("mmc: Add support for downgrading > > HS200/HS400 to HS mode"), it add a parameter in mmc_set_card_speed() > > which indicates that the HS200/HS400 to HS downgrade is happening. > > > > During the HS400 initialization, first select to HS200, and config the > > related clock rate, then downgrade to HS mode. So here also need to > > config the downgrade value to be true, make sure in the function > > mmc_set_card_speed(), after switch to HS mode, first config the clock > > rate, then read the EXT_CSD. Otherwise read EXT_CSD in HS mode at > > wrong clock rate, e.g. 200MHz, may lead to uncertain result. > > I think the fix is right, but the reasoning for it is not. > > If you call mmc_set_card_speed() with hsdowngrade=true, it will result in > calling __mmc_switch() with send_status=false , which in turn means that > after issuing the MMC_CMD_SWITCH command, the code won't poll the card > using MMC_CMD_SEND_STATUS, but just wait a bit and then switch the bus > properties. This is indeed required when switching bus properties. > And that's what I think was making your card unstable. > > Is that the case ?
Sorry for the tardy reply, I miss the email last week. No, if without this patch, even I add the dealy after the switch command, eMMC still stuck after the CMD8. The main issue is that, in mmc_set_card_speed, if the bus mode the HS mode, it will send CMD8 to get the EXT_CSD, but the clock is still 200MHz at that time. It is wrong that EMMC output data in HS mode at 200MHz. Best Regards Haibo Chen > > > Test on i.MX8QM MEK board, some Micron eMMC will stuck in transfer > > mode in this case, and USDHC will never get data transfer complete > > status, cause the uboot hang. > > > > Signed-off-by: Haibo Chen <haibo.c...@nxp.com> > > --- > > drivers/mmc/mmc.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index > > 1c1527cc74..55d3560b30 100644 > > --- a/drivers/mmc/mmc.c > > +++ b/drivers/mmc/mmc.c > > @@ -1892,8 +1892,7 @@ static int mmc_select_hs400(struct mmc *mmc) > > } > > > > /* Set back to HS */ > > - mmc_set_card_speed(mmc, MMC_HS, false); > > - mmc_set_clock(mmc, mmc_mode2freq(mmc, MMC_HS), false); > > + mmc_set_card_speed(mmc, MMC_HS, true); > > > > err = mmc_switch(mmc, EXT_CSD_CMD_SET_NORMAL, > EXT_CSD_BUS_WIDTH, > > EXT_CSD_BUS_WIDTH_8 | EXT_CSD_DDR_FLAG); > > > > > -- > Best regards, > Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
