[U-Boot] [PATCH] mmc: support hs400 enhanced strobe mode

[Fabio Estevam]

Hi Peng,

On Mon, Apr 15, 2019 at 10:33 PM Peng Fan <peng.fan at nxp.com> wrote:
>
> eMMC 5.1+ supports HS400 Enhances Strobe mode without the need for
> tuning procedure.
> The flow is as following:
>  - set HS_TIMIMG (Highspeed)
>  - Host change freq to <= 52Mhz
>  - set the bus width to Enhanced strobe and DDR8Bit(CMD6),
>    EXT_CSD[183] = 0x86 instead of 0x80
>  - set HS_TIMING to 0x3 (HS400)
>  - Host change freq to <= 200Mhz
>  - Host select HS400 enhanced strobe complete
>
> Signed-off-by: Peng Fan <peng.fan at nxp.com>
> ---
>
> This is actually a resend of https://patchwork.ozlabs.org/patch/1018188/
> which got no response.
> Rebased on master.
>
>
>  drivers/mmc/Kconfig      | 12 ++++++++
>  drivers/mmc/mmc-uclass.c | 15 +++++++++
>  drivers/mmc/mmc.c        | 79 +++++++++++++++++++++++++++++++++++++++++++++++-
>  include/mmc.h            | 15 +++++++++
>  4 files changed, 120 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
> index 04a4e7716f..3ef7580a43 100644
> --- a/drivers/mmc/Kconfig
> +++ b/drivers/mmc/Kconfig
> @@ -111,6 +111,18 @@ config SPL_MMC_UHS_SUPPORT
>           cards. The IO voltage must be switchable from 3.3v to 1.8v. The bus
>           frequency can go up to 208MHz (SDR104)
>
> +config MMC_HS400_ES_SUPPORT
> +       bool "enable HS400 Enhanced Strobe support"
> +       help
> +         The HS400 Enhanced Strobe mode is support by some eMMC. The bus frequency is up to
> +         200MHz. This mode does not tune the IO.

Is there any board that can select this option?

Otherwise it will be just dead code.

Thanks