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 18:49:17 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Roger Quadros <rogerq@...com>,
	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 07/07/2015 05:37 PM, Roger Quadros wrote:
> On 07/07/15 17:35, Roger Quadros wrote:
>> 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.
>
> On second thoughts
>
> device->pins are not defined if CONFIG_PINCTRL is not set.
> so we can't remove the #ifdef.

May be you can use [devm_]pinctrl_get?

>>>
>>>> +    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;
>>>>   }
>>>>

-- 
regards,
-grygorii
--
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