2016-03-04 15:56 GMT+09:00 Masahiro Yamada yamada.masahiro@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@socionext.com
Applied to u-boot-uniphier/master.