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

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  Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional Uwe Kleine-König   <u.kleine-koenig@pengutronix.de> - 2015-11-18 08:30 +0100
    Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional Li Yang <leoli@freescale.com> - 2015-11-19 00:00 +0100
      Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional Uwe Kleine-König   <u.kleine-koenig@pengutronix.de> - 2015-11-19 09:10 +0100
        Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional Li Yang <leoli@freescale.com> - 2015-11-20 19:10 +0100

#1271893 — Re: [PATCH] i2c: imx: make bus recovery through pinctrl optional

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@freescale.com>
> Cc: Gao Pan <b54642@freescale.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:

	i2c_imx->pinctrl = devm_pinctrl_get(&pdev->dev);
	if (IS_ERR(i2c_imx->pinctrl)) {
		ret = PTR_ERR(i2c_imx->pinctrl);
		goto errorhandling;
	}

	if (i2c_imx->pinctrl)
		i2c_imx_init_recovery_info(i2c_imx, pdev);
	else
		dev_info(&pdev->dev, "can't get pinctrl, bus recovery feature disabled\n");


right?

Uwe Kleine-König

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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#1272653

On Wed, Nov 18, 2015 at 1:24 AM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.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@freescale.com>
>> Cc: Gao Pan <b54642@freescale.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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#1272912

Hello,

Cc += Linus Walleij, linux-gpio

On Wed, Nov 18, 2015 at 04:59:11PM -0600, Li Yang wrote:
> On Wed, Nov 18, 2015 at 1:24 AM, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > On Tue, Nov 17, 2015 at 06:02:59PM -0600, Li Yang wrote:
> >> @@ -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.

IMHO you shouldn't ignore -ENOMEM from devm_pinctrl_get but just the
case for "there was no pinctrl specified in dt". Also consider the i2c
driver is loaded before the pinctrl driver and devm_pinctrl_get returns
-EPROBE_DEFER (I assume it does, didn't check), this should be handled.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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#1274327

On Thu, Nov 19, 2015 at 2:08 AM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> Hello,
>
> Cc += Linus Walleij, linux-gpio
>
> On Wed, Nov 18, 2015 at 04:59:11PM -0600, Li Yang wrote:
>> On Wed, Nov 18, 2015 at 1:24 AM, Uwe Kleine-König
>> <u.kleine-koenig@pengutronix.de> wrote:
>> > On Tue, Nov 17, 2015 at 06:02:59PM -0600, Li Yang wrote:
>> >> @@ -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.
>
> IMHO you shouldn't ignore -ENOMEM from devm_pinctrl_get but just the
> case for "there was no pinctrl specified in dt". Also consider the i2c
> driver is loaded before the pinctrl driver and devm_pinctrl_get returns
> -EPROBE_DEFER (I assume it does, didn't check), this should be handled.

Make sense.   -EPROBE_DEFER should be honored.  Maybe it's good to
check the -ENOMEM too.  I will send a new version.

Thanks,
Leo
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