[EXT] Re: [PATCH 4/4] imx8mq_evk: Enable the USB3.0 host port

[Bough Chen]

> -----Original Message-----
> From: Ye Li
> Sent: 2021年2月27日 14:05
> To: festevam at gmail.com; Bough Chen <haibo.chen at nxp.com>
> Cc: Peng Fan <peng.fan at nxp.com>; u-boot at lists.denx.de; dl-uboot-imx
> <uboot-imx at nxp.com>; sbabic at denx.de
> Subject: Re: [EXT] Re: [PATCH 4/4] imx8mq_evk: Enable the USB3.0 host port
> 
> Hi Fabio,
> 
> On Thu, 2021-02-25 at 10:49 -0300, Fabio Estevam wrote:
> > Caution: EXT Email
> >
> > Hi Ye Li,
> >
> > On Thu, Feb 25, 2021 at 10:34 AM Ye Li <ye.li at nxp.com> wrote:
> >
> > >
> > > Sure, I have tested it on 8mq evk. I can reproduce the two issues
> > > you met.
> > > The first issue is caused by the ALIGN. The implementation of
> > > standard ALIGN requires the aligned size to be power of 2. But the
> > > ALIGN in imx8mimage does not have this requirement. So below result
> > > is wrong by using the standard ALIGN. Your fix should be OK for this
> > > issue.
> > Good, could you please reply to my ALIGN macro patch with your
> > Tested-by tag then?
> >
> Replied it.
> 
> > >
> > > For the second issue, I did not debug into it. But our vendor tree
> > > also uses off-on-delay-us in both u-boot and kernel. So it is likely
> > > caused by other change.
> > Considering we are already at 2021.04-rc2, I think it would be safer
> > to go with my patch that removes off-on-delay-us.
> >
> > What do you think?
> >
> > Thanks
> My debug shows the issue is triggered by below commit:
> 
> commit 9098682200e6cca4b776638a51200dafa16f50fb
> Author: Haibo Chen <haibo.chen at nxp.com>
> Date:   Tue Sep 22 18:11:43 2020 +0800
> 
>     mmc: fsl_esdhc_imx: remove the 1ms delay before sending command
> 
>     This 1ms delay before sending command already exist from the beginning
>     of the fsl_esdhc driver added in year 2008. Now this driver has been
>     split for two files: fsl_esdhc.c and fsl_esdhc_imx.c.
> fsl_esdhc_imx.c
>     only for i.MX series. i.MX series esdhc/usdhc do not need this 1ms delay
>     before sending any command. So remove this 1ms, this will save a lot
>     time if handling a large mmc data.
> 
>     Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
> 
> 
> The first "go idle" command in mmc_get_op_cond seems not put SD card to
> idle status, but if adding a delay before it (like 1ms delay), then everything
> works. This commit removed 1ms delay in sending command, so the issue is
> triggered.  The root cause might be "startup-delay-us"
> needed for this regulator to reach a threshold voltage for SD working.
> Below change also can fix the issue.
> 
> --- a/arch/arm/dts/imx8mq-evk-u-boot.dtsi
> +++ b/arch/arm/dts/imx8mq-evk-u-boot.dtsi
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: (GPL-2.0 OR MIT)
> 
>  &reg_usdhc2_vmmc {
> +       startup-delay-us = <1000>;
>         u-boot,off-on-delay-us = <20000>;
>  };
> 
> 
> @Haibo, Could you help looking into the issue. What's your opinion to add the
> startup-delay-us or revert your commit?
> 

Hi Fabio,

I co-debug with Ye, and find the issue is also related with clock enable/disable. For current logic on imx usdhc, hardware automatically gate off the card clock when idle.
So before the first command "go idle", there is no clock on the clock line, which not align with the sd spec.
Refer to SD3.0 spec 6.4.1 Power UP
The host shall supply power to the card so that the voltage is reached to Vdd_min within 250ms and
start to supply at least 74 SD clocks to the SD card with keeping CMD line to high. In case of SPI
mode, CS shall be held to high during 74 clock cycles

if we give the card the correct clock rate before the first "go idle" command, this issue gone.
Please try to apply the patch I send on 2021/1/27   [PATCH] mmc: fsl_esdhc_imx: use VENDORSPEC_FRC_SDCLK_ON to control card clock output 

> Best regards,
> Ye Li
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