linux-kernel - Re: [PATCH 1/2] net: can: c_can: Fix default pinmux glitch at init

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Date:	Tue, 7 Jul 2015 17:35:42 +0300
From:	Roger Quadros <rogerq@...com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>, <wg@...ndegger.com>,
	<tony@...mide.com>
CC:	<jay.schroeder@...min.com>, <linux-can@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] net: can: c_can: Fix default pinmux glitch at init

On 07/07/15 17:33, Marc Kleine-Budde wrote:
> On 07/07/2015 04:27 PM, Roger Quadros wrote:
>> From: "J.D. Schroeder" <jay.schroeder@...min.com>
>>
>> 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
>>
>> Signed-off-by: J.D. Schroeder <jay.schroeder@...min.com>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>   drivers/net/can/c_can/c_can.c | 13 ++++++++++++-
>>   1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
>> index 041525d..66e98e7 100644
>> --- a/drivers/net/can/c_can/c_can.c
>> +++ b/drivers/net/can/c_can/c_can.c
>> @@ -605,7 +605,18 @@ 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);
>> +#ifdef CONFIG_PINCTRL
>
> Please remove the ifdef, AFAICS there are static inline noop functions
> if CONFIG_PINCTRL switched off.

yes, you are right.

cheers,
-roger

>
>> +	if (priv->device->pins) {
>> +		struct pinctrl_state *s;
>> +
>> +		/* Attempt to use "active" if available else use "default" */
>> +		s = pinctrl_lookup_state(priv->device->pins->p, "active");
>> +		if (!IS_ERR(s))
>> +			pinctrl_select_state(priv->device->pins->p, s);
>> +		else
>> +			pinctrl_pm_select_default_state(dev->dev.parent);
>> +	}
>> +#endif
>>   	return 0;
>>   }
>>
>>
>
> Marc
>
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