linux-kernel - [PATCH 4.3 082/125] pinctrl: uniphier: set input-enable before pin-muxing

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Date:	Mon,  7 Dec 2015 10:01:35 -0500
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Dai Okamura <okamura.dai@...ionext.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 4.3 082/125] pinctrl: uniphier: set input-enable before pin-muxing

4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masahiro Yamada <yamada.masahiro@...ionext.com>

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@...ionext.com>
Reported-by: Dai Okamura <okamura.dai@...ionext.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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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