[PATCH] imx8mm_beacon: Enable HS400 on MMC controller

[ZHIZHIKIN Andrey]

Hello Adam,

> -----Original Message-----
> From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Adam Ford
> Sent: Saturday, December 5, 2020 2:00 AM
> To: u-boot at lists.denx.de
> Cc: aford at beaconembedded.com; Adam Ford <aford173 at gmail.com>
> Subject: [PATCH] imx8mm_beacon: Enable HS400 on MMC controller
> 
> 
> The i.MX8MM is capable of HS400.  Enable it in both U-Boot and SPL for faster
> throughput.

I'm not quite sure if those high-speed modes would be required to be enabled for
SPL...

Even though the support for those modes is provided in SPL build, there might be
a little benefit of having it enabled as the only thing SPL would need to fetch from 
storage medias would be U-Boot itself, and the difference in access time between
high speed modes enabled or disabled for this task is quite negligible. The downside
there would rather be an increase in SPL size to accommodate enabled code paths.

I was contemplating myself to have those included, but decided to op-out from it
as I could not justify the benefit of it.

Do you see any particular use-case where it would be beneficial to enable those modes
in SPL? If so - can you please share them, as if it would turn out to be beneficial - I might
also turn them on in EVK configs.

> 
> Signed-off-by: Adam Ford <aford173 at gmail.com>
> 
> diff --git a/configs/imx8mm_beacon_defconfig
> b/configs/imx8mm_beacon_defconfig index c5d331f617..49d5453078 100644
> --- a/configs/imx8mm_beacon_defconfig
> +++ b/configs/imx8mm_beacon_defconfig
> @@ -70,6 +70,13 @@ CONFIG_DM_I2C=y
>  CONFIG_SYS_I2C_MXC=y
>  CONFIG_DM_MMC=y
>  CONFIG_SUPPORT_EMMC_BOOT=y
> +CONFIG_MMC_IO_VOLTAGE=y
> +CONFIG_SPL_MMC_IO_VOLTAGE=y
> +CONFIG_MMC_UHS_SUPPORT=y
> +CONFIG_SPL_MMC_UHS_SUPPORT=y
> +CONFIG_MMC_HS400_ES_SUPPORT=y
> +CONFIG_MMC_HS400_SUPPORT=y
> +CONFIG_SPL_MMC_HS400_SUPPORT=y
>  CONFIG_FSL_USDHC=y
>  CONFIG_PHYLIB=y
>  CONFIG_PHY_ATHEROS=y
> --
> 2.25.1

-- andrey