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6351cac92a
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. Cc: Alexandre Torgue <alexandre.torgue@st.com> Cc: Ludovic Barre <ludovic.barre@st.com> Tested-by: Yann Gautier <yann.gautier@foss.st.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Marek Vasut <marex@denx.de> Link: https://lore.kernel.org/r/20210124170258.32862-2-marex@denx.de Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
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Please read the Documentation/process/changes.rst file, as it contains the
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