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

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Date:	Wed, 8 Jul 2015 11:13:23 +0300
From:	Roger Quadros <rogerq@...com>
To:	Grygorii Strashko <grygorii.strashko@...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 07/07/15 18:49, Grygorii Strashko wrote:
> 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?

Why should we do that? The device core has already done the 
pinctrl_get() and it is available in device->pins->p.

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;
>>>>>   }
>>>>>
>
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