[U-Boot] [PATCH] pinctrl: uniphier: set input-enable before pin-muxing

[Masahiro Yamada]

2016-03-04 15:56 GMT+09:00 Masahiro Yamada <yamada.masahiro at socionext.com>:
> While IECTRL is disabled, input signals are pulled-down internally.
> If pin-muxing is set up first, glitch signals (Low to High transition)
> might be input to hardware blocks.
>
> Bad case scenario:
> [1] The hardware block is already running before pinctrl is handled.
>    (the reset is de-asserted by default or by a firmware, for example)
> [2] The pin-muxing is set up.  The input signals to hardware block
>    are pulled-down by the chip-internal biasing.
> [3] The pins are input-enabled.  The signals from the board reach the
>     hardware block.
>
> Actually, one invalid character is input to the UART blocks for such
> SoCs as PH1-LD4, PH1-sLD8, where UART devices start to run at the
> power on reset.
>
> To avoid such problems, pins should be input-enabled before muxing.
>
> [ ported from Linux commit bac7f4c1bf5e7c6ccd5bb71edc015b26c77f7460 ]
>
> Fixes: 5dc626f83619 ("pinctrl: uniphier: add UniPhier pinctrl core support")
> Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>


Applied to u-boot-uniphier/master.


-- 
Best Regards
Masahiro Yamada