linux-kernel - [PATCH 3.19.y-ckt 079/107] can: c_can: Fix default pinmux glitch at init

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Message-Id: <1438811379-384-80-git-send-email-kamal@canonical.com>
Date:	Wed,  5 Aug 2015 14:49:11 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	"J.D. Schroeder" <jay.schroeder@...min.com>,
	Roger Quadros <rogerq@...com>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 079/107] can: c_can: Fix default pinmux glitch at init

3.19.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

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

From: "J.D. Schroeder" <jay.schroeder@...min.com>

commit 033365191136c97f88c81b7bd0011414db28bb4e upstream.

The previous change 3973c526ae9c (net: can: c_can: Disable pins when CAN
interface is down) causes a slight glitch on the pinctrl settings when used.
Since commit ab78029 (drivers/pinctrl: grab default handles from device core),
the device core will automatically set the default pins. This causes the pins
to be momentarily set to the default and then to the sleep state in
register_c_can_dev(). By adding an optional "enable" state, boards can set the
default pin state to be disabled and avoid the glitch when the switch from
default to sleep first occurs. If the "enable" state is not available
c_can_pinctrl_select_state() falls back to using the "default" pinctrl state.

[Roger Q] - Forward port to v4.2 and use pinctrl_get_select().

Signed-off-by: J.D. Schroeder <jay.schroeder@...min.com>
Signed-off-by: Roger Quadros <rogerq@...com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@...com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/net/can/c_can/c_can.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index c672c4d..84540b0 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -592,6 +592,7 @@ static int c_can_start(struct net_device *dev)
 {
 	struct c_can_priv *priv = netdev_priv(dev);
 	int err;
+	struct pinctrl *p;

 	/* basic c_can configuration */
 	err = c_can_chip_config(dev);
@@ -604,8 +605,13 @@ static int c_can_start(struct net_device *dev)

 	priv->can.state = CAN_STATE_ERROR_ACTIVE;

-	/* activate pins */
-	pinctrl_pm_select_default_state(dev->dev.parent);
+	/* Attempt to use "active" if available else use "default" */
+	p = pinctrl_get_select(priv->device, "active");
+	if (!IS_ERR(p))
+		pinctrl_put(p);
+	else
+		pinctrl_pm_select_default_state(priv->device);
+
 	return 0;
 }

-- 
1.9.1

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