[PATCH] Revert "mmc: fsl_esdhc_imx: add wait_dat0() support"

Marek Vasut marex at denx.de
Sun Feb 13 22:48:57 CET 2022

On 2/7/22 08:59, Bough Chen wrote:
>> -----Original Message-----
>> From: Marek Vasut [mailto:marex at denx.de]
>> Sent: 2022年1月29日 1:37
>> To: Jaehoon Chung <jh80.chung at samsung.com>; u-boot at lists.denx.de
>> Cc: sbabic at denx.de; Bough Chen <haibo.chen at nxp.com>; Igor Opaniuk
>> <igor.opaniuk at foundries.io>; Peng Fan <peng.fan at nxp.com>
>> Subject: Re: [PATCH] Revert "mmc: fsl_esdhc_imx: add wait_dat0() support"
>> On 1/28/22 08:30, Jaehoon Chung wrote:
>>> Hi Marek,
>> Hi,
>>> On 1/28/22 12:40, Marek Vasut wrote:
>>>> This reverts commit b5874b552ffa09bc1dc5dec6b5dd376c62dab45d.
>>>> It seems the iMX8MM SDHC controller always reports DAT0 line status
>>>> as zero after voltage switch at the end of mmc_switch_voltage(), even
>>>> if it is supposed to be high and scope confirms the DAT0 is high.
>>>> Reverting this patch makes SDR104 work on iMX8MM, however, it is not
>>>> clear why the DAT0 status is not correctly reported by the
>>>> controller.
>>> I didn't have an imx8mm board, so I wonder that other boards which is using
>> fsl_esdhci_imx driver have same problem.
>> I have multiple 8mm, just not the 8mm-evk.
>>> I'm not sure...I remember that some controller doesn't support a busy signal.
>>> In kernel driver, also doesn't report correct status?
>> Kernel doesn't use this DAT0 readback, that's why it works in kernel.
>> U-Boot has been augmented with this DAT0 readback some time ago, I just
>> noticed it on an 8mm board recently that it doesn't really work. There is also no
>> errata.
>> I think it would be good to have NXP check this.
> Hi,
> The issue you meet should be related to one patch that was revert recently, refer to
> Commit f132aab40327 " Revert "mmc: fsl_esdhc_imx: use VENDORSPEC_FRC_SDCLK_ON to control card clock output""
> The issue you meet seems the same as what I mentioned in my original commit log, I paste in the end.
> Revert this patch because we did find this patch has some side effect, like enlarge the whole boot up time about 20s.
> If you will, you can add back this patch on your side, and test it.
> I will send one new patch this week, to fix issue and avoid side effect.
> Best Regards
> Haibo Chen
> commit 63756575b42b8b4fb3f59cbbf0cedf03331bc2d2
> Author: Haibo Chen <haibo.chen at nxp.com>
> Date:   Wed Mar 3 17:05:46 2021 +0800
>      mmc: fsl_esdhc_imx: use VENDORSPEC_FRC_SDCLK_ON to control card clock output
>      For FSL_USDHC, it do not implement VENDORSPEC_CKEN/PEREN/HCKEN/IPGEN, these
>      are reserved bits. Instead, use VENDORSPEC_FRC_SDCLK_ON to gate on/off the
>      card clock output.
>      After commit b5874b552ffa ("mmc: fsl_esdhc_imx: add wait_dat0() support"),
>      we meet SD3.0 card can't work at UHS mode, mmc_switch_voltage() fail because
>      the second mmc_wait_dat0 return -ETIMEDOUT. According to SD spec, during
>      voltage switch, need to gate off/on the card clock. If not set the FRC_SDCLK_ON,
>      after CMD11, hardware will gate off the card clock automatically, so card do
>      not detect the clock off/on behavior, so will draw the data0 line low until
>      next command.
>      Fixes: b5874b552ffa ("mmc: fsl_esdhc_imx: add wait_dat0() support")
>      Tested-by: Tim Harvey <tharvey at gateworks.com>
>      Signed-off-by: Haibo Chen <haibo.chen at nxp.com>

I see you already managed to post follow up patches, I already tested 
those and they indeed help. I'll provide RB shortly, thanks.

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