pinctrl: uniphier: set input-enable before pin-muxing

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@socionext.com>
Reported-by: Dai Okamura <okamura.dai@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c b/drivers/pinctrl/uniphier/pinctrl-uniphier-core.c
index 918f3b643f1b..589872cc8adb 100644
--- 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(struct pinctrl_dev *pctldev, unsigned pin,
         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(struct pinctrl_dev *pctldev, unsigned pin,
                         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,