4.3-stable review patch. If anyone has any objections, please let me know.
------------------
From: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
commit bac7f4c1bf5e7c6ccd5bb71edc015b26c77f7460 upstream.
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.
Fixes: 6e9088920258 ("pinctrl: UniPhier: add UniPhier pinctrl core support")
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Reported-by: Dai Okamura <okamura.dai@xxxxxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/pinctrl/uniphier/pinctrl-uniphier-core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
+++ b/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
@@ -539,6 +539,12 @@ static int uniphier_pmx_set_one_mux(stru
unsigned reg, reg_end, shift, mask;
int ret;
+ /* some pins need input-enabling */
+ ret = uniphier_conf_pin_input_enable(pctldev,
+ &pctldev->desc->pins[pin], 1);
+ if (ret)
+ return ret;
+
reg = UNIPHIER_PINCTRL_PINMUX_BASE + pin * mux_bits / 32 * reg_stride;
reg_end = reg + reg_stride;
shift = pin * mux_bits % 32;
@@ -563,9 +569,7 @@ static int uniphier_pmx_set_one_mux(stru
return ret;
}
- /* some pins need input-enabling */
- return uniphier_conf_pin_input_enable(pctldev,
- &pctldev->desc->pins[pin], 1);
+ return 0;
}
static int uniphier_pmx_set_mux(struct pinctrl_dev *pctldev,
--
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