[PATCH] Revert "mmc: fsl_esdhc_imx: remove the 1ms delay before sending command"

[Bough Chen]

> -----Original Message-----
> From: Fabio Estevam [mailto:festevam at gmail.com]
> Sent: 2021年2月27日 21:54
> To: Peng Fan <peng.fan at nxp.com>
> Cc: u-boot at lists.denx.de; lorusak at gmail.com;
> andrey.zhizhikin at leica-geosystems.com; Ye Li <ye.li at nxp.com>; Bough Chen
> <haibo.chen at nxp.com>; sbabic at denx.de; trini at konsulko.com; Fabio Estevam
> <festevam at gmail.com>
> Subject: [PATCH] Revert "mmc: fsl_esdhc_imx: remove the 1ms delay before
> sending command"
> 
> Removing the 1ms delay before sending command causes a regression on
> imx8mq-evk where the SD card cannot be accessed.
> 
> Since this 1ms delay has been present since the driver introduction in
2008,
> keep it to avoid regressions.
> 
> This reverts commit 9098682200e6cca4b776638a51200dafa16f50fb.
> 

Hi Fabio,

This 1ms delay exist in esdhc_send_cmd_common, which means every time we
send a command, will delay 1ms, which will involve a huge delay overall for
the whole u-boot cycle.
For the issue you meet, I already find the root cause, and already reply in
the mail loop: [EXT] Re: [PATCH 4/4] imx8mq_evk: Enable the USB3.0 host port
So I think no need to involve this 1ms back again.

Best regards
Haibo Chen

> Reported-by: Ye Li <ye.li at nxp.com>
> Signed-off-by: Fabio Estevam <festevam at gmail.com>
> ---
>  drivers/mmc/fsl_esdhc_imx.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/mmc/fsl_esdhc_imx.c b/drivers/mmc/fsl_esdhc_imx.c
index
> e0e132698e30..a0a5c8960563 100644
> --- a/drivers/mmc/fsl_esdhc_imx.c
> +++ b/drivers/mmc/fsl_esdhc_imx.c
> @@ -463,6 +463,13 @@ static int esdhc_send_cmd_common(struct
> fsl_esdhc_priv *priv, struct mmc *mmc,
>  	while (esdhc_read32(&regs->prsstat) & PRSSTAT_DLA)
>  		;
> 
> +	/* Wait at least 8 SD clock cycles before the next command */
> +	/*
> +	 * Note: This is way more than 8 cycles, but 1ms seems to
> +	 * resolve timing issues with some cards
> +	 */
> +	udelay(1000);
> +
>  	/* Set up for a data transfer if we have one */
>  	if (data) {
>  		err = esdhc_setup_data(priv, mmc, data);
> --
> 2.25.1

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