linux-kernel - Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional

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Message-ID: <CADRPPNQZye7t2biS2Z8p3y7O6=xw4UcOLRC5ngs2Qvuh0UHXGg@mail.gmail.com>
Date:	Wed, 18 Nov 2015 16:59:11 -0600
From:	Li Yang <leoli@...escale.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Gao Pan <b54642@...escale.com>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional

On Wed, Nov 18, 2015 at 1:24 AM, Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
> Hello,
>
> On Tue, Nov 17, 2015 at 06:02:59PM -0600, Li Yang wrote:
>> Since commit 1c4b6c3bcf30 ("i2c: imx: implement bus recovery") the driver
>> starts to use gpio/pinctrl to do i2c bus recovery.  But pinctrl is not
>> always available for platforms using this driver such as ls1021a and
>> ls1043a, and the device tree binding also mentioned this gpio based
>> recovery mechanism as optional.  The patch make it really optional that
>> the probe function won't bailout when pinctrl is not available and it
>> won't try to register recovery functions if pinctrl is NULL when the
>> PINCTRL is not enabled at all.
>>
>> Signed-off-by: Li Yang <leoli@...escale.com>
>> Cc: Gao Pan <b54642@...escale.com>
>> ---
>>  drivers/i2c/busses/i2c-imx.c | 13 ++++++-------
>>  1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> index 1e4d99d..7813153 100644
>> --- a/drivers/i2c/busses/i2c-imx.c
>> +++ b/drivers/i2c/busses/i2c-imx.c
>> @@ -1086,12 +1086,6 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>               return ret;
>>       }
>>
>> -     i2c_imx->pinctrl = devm_pinctrl_get(&pdev->dev);
>> -     if (IS_ERR(i2c_imx->pinctrl)) {
>> -             ret = PTR_ERR(i2c_imx->pinctrl);
>> -             goto clk_disable;
>> -     }
>> -
>>       /* Request IRQ */
>>       ret = devm_request_irq(&pdev->dev, irq, i2c_imx_isr, 0,
>>                               pdev->name, i2c_imx);
>> @@ -1125,7 +1119,12 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>               goto clk_disable;
>>       }
>>
>> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
>> +     /* optional bus recovery feature through pinctrl */
>> +     i2c_imx->pinctrl = devm_pinctrl_get(&pdev->dev);
>> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
>> +             dev_info(&pdev->dev, "can't get pinctrl, bus recovery feature disabled\n");
>> +     else
>> +             i2c_imx_init_recovery_info(i2c_imx, pdev);
>
> I'm pretty sure this is wrong. If pinctrl isn't available
> devm_pinctrl_get returns NULL? But AFAIK you must not ignore an error,
> so the better thing to do is:

If CONFIG_PINCTRL is not enabled, the devm_pinctrl_get() will return
NULL directly as defined in the include/linux/pinctrl/consumer.h.

If CONFIG_PINCTRL is enabled because we are using a multi-platform
image but the actual hardware used doesn't have a pinctrl driver or
pinctrl device tree nodes.  It is expected that the devm_pinctrl_get()
will return error.  But as the pinctrl is only used for bus recovery
which is just an optional function of this driver.  We shouldn't
bailout the probe but keep the driver working without the bus recovery
function.  As for generic errors like (!dev) or out-of-memory, the
probe will fail elsewhere anyway.

Regards,
Leo
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