Re: [added to the 3.18 stable tree] can: c_can: Fix default pinmux glitch at init

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 07/31/2015 04:10 AM, Sasha Levin wrote:
> From: Heiko Carstens <heiko.carstens@de.ibm.com>
> 
> This patch has been added to the 3.18 stable tree. If you have any
> objections, please let us know.
> 
> ===============
> 
> [ Upstream commit 033365191136c97f88c81b7bd0011414db28bb4e ]
> 
> 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@garmin.com>
> Signed-off-by: Roger Quadros <rogerq@ti.com>
> Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
> Cc: linux-stable <stable@vger.kernel.org>
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> ---
>  arch/s390/kernel/process.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
> index ed84cc2..9b72e68 100644
> --- a/arch/s390/kernel/process.c
> +++ b/arch/s390/kernel/process.c
> @@ -171,7 +171,7 @@ asmlinkage void execve_tail(void)
>  {
>  	current->thread.fp_regs.fpc = 0;
>  	if (MACHINE_HAS_IEEE)
> -		asm volatile("sfpc %0,%0" : : "d" (0));
> +		asm volatile("sfpc %0" : : "d" (0));
>  }
>  
>  /*
> 

The original upstream patch looked like this:

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 041525d2595c..5d214d135332 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;
 }

Marc

-- 
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