On 3/25/19 1:10 PM, Tom Rini wrote:
On Mon, Mar 25, 2019 at 12:16:53PM +0100, Marek Vasut wrote:
On 3/25/19 11:24 AM, BOUGH CHEN wrote:
-----Original Message----- From: Marek Vasut [mailto:marek.vasut@gmail.com] Sent: 2019年3月18日 19:53 To: BOUGH CHEN haibo.chen@nxp.com; jh80.chung@samsung.com; trini@konsulko.com Cc: marek.vasut+renesas@gmail.com; Ye Li ye.li@nxp.com; dl-uboot-imx uboot-imx@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.
OK, that makes sense.
Do we need a re-worded commit message then or no? Thanks!
A bit wouldn't hurt, to clarify things.