[Linux-stm32] [PATCH 2/4] mmc: mmci: Add support for probing bus voltage level translator

[Linus Walleij]

On Sat, Jan 16, 2021 at 7:04 PM Marek Vasut <marex at denx.de> wrote:

> Add support for testing whether bus voltage level translator is present
> and operational. This is useful on systems where the bus voltage level
> translator is optional, as the translator can be auto-detected by the
> driver and the feedback clock functionality can be disabled if it is
> not present.
>
> This requires additional pinmux state, "init", where the CMD, CK, CKIN
> lines are not configured, so they can be claimed as GPIOs early on in
> probe(). The translator test sets CMD high to avoid interfering with a
> card, and then verifies whether signal set on CK is detected on CKIN.
> If the signal is detected, translator is present, otherwise the CKIN
> feedback clock are disabled.
>
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Alexandre Torgue <alexandre.torgue at st.com>
> Cc: Linus Walleij <linus.walleij at linaro.org>
> Cc: Ludovic Barre <ludovic.barre at st.com>
> Cc: Ulf Hansson <ulf.hansson at linaro.org>
> Cc: linux-stm32 at st-md-mailman.stormreply.com

Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij