pinctrl: freescale: avoid overwriting pin config when freeing GPIO
diff mbox

Message ID 1a113c0f-4ee3-e61a-8927-b5e8b558822c@mentor.com
State New
Headers show

Commit Message

Vladimir Zapolskiy Sept. 28, 2016, 12:07 p.m. UTC
On 09/28/2016 06:38 AM, Stefan Agner wrote:
> On 2016-09-27 19:00, Viresh Kumar wrote:
>> On 27-09-16, 12:34, Stefan Agner wrote:
>>> Added Viresh Kumar to the discussion, he implemented the I2C recovery
>>> functions.
>>>
>>> Yes, reordering the pinctrl/gpio_free calls would fix the problem too.
>>>
>>> However, I guess there is no explicit rule to that ("request/free GPIOs
>>> only when they are muxed as GPIO"), so I think of it that the issue is
>>> actually in the pinctrl driver.
>>>
>>> On top of that it is not entirely trivial to reorder the calls the way
>>> i2c_generic_gpio_recovery and i2c_generic_recovery are set up right now.
>>
>> AFAICT, these routines don't touch the muxing part at all. Perhaps it is done
>> internally by the GPIO calls. Can you please elaborate the exact change you are
>> hinting towards here ?
>
> The i.MX I2C driver touches the pinctrl in its prepare/unprepare
> callbacks.
>
> So, on a i.MX or Vybrid, the call chain looks like this:
>
> i2c_generic_gpio_recovery
>     -> i2c_get_gpios_for_recovery
>        -> gpio_request_one
>     -> i2c_generic_recovery
>        -> prepare_recovery (i2c_imx_prepare_recovery)
>           -> pinctrl_select_state [gpio]
>        -> unprepare_recovery (i2c_imx_unprepare_recovery)
>           -> pinctrl_select_state [default]
>     -> i2c_put_gpios_for_recovery
>        -> gpio_free

I would expect that the change below improves the situation, but I didn't
perform any tests and here the core change is governed by the accepted
i.MX i2c bus driver specific changes, thus conceptually it may be incorrect:



Alternatively you may consider to add contents of i2c_get_gpios_for_recovery()
into i2c_imx_prepare_recovery(), contents of i2c_put_gpios_for_recovery() into
i2c_imx_unprepare_recovery() in the i.MX I2C bus driver and change the recovery
callback .recover_bus to i2c_generic_scl_recovery().

>
> And for the pinctrl/GPIO driver of Vybrid this is actually a problem
> because gpio_free disables the output driver of the pad, and when that
> happens after the (I2C) default pinctrl state gets selected the pad is
> no longer active.
>

--
With best wishes,
Vladimir
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Comments

Viresh Kumar Sept. 29, 2016, 6:46 a.m. UTC | #1
On 28-09-16, 15:07, Vladimir Zapolskiy wrote:
> I would expect that the change below improves the situation, but I didn't
> perform any tests and here the core change is governed by the accepted
> i.MX i2c bus driver specific changes, thus conceptually it may be incorrect:
> 
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index da3a02ef4a31..3a4f59c3c3e6 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -697,9 +697,6 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
>  	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
>  	int i = 0, val = 1, ret = 0;
> -	if (bri->prepare_recovery)
> -		bri->prepare_recovery(adap);
> -
>  	bri->set_scl(adap, val);
>  	ndelay(RECOVERY_NDELAY);
> @@ -725,22 +722,34 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
>  		ndelay(RECOVERY_NDELAY);
>  	}
> -	if (bri->unprepare_recovery)
> -		bri->unprepare_recovery(adap);
> -
>  	return ret;
>  }
>  int i2c_generic_scl_recovery(struct i2c_adapter *adap)
>  {
> -	return i2c_generic_recovery(adap);
> +	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
> +	int ret;
> +
> +	if (bri->prepare_recovery)
> +		bri->prepare_recovery(adap);
> +
> +	ret = i2c_generic_recovery(adap);
> +
> +	if (bri->unprepare_recovery)
> +		bri->unprepare_recovery(adap);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);
>  int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
>  {
> +	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
>  	int ret;
> +	if (bri->prepare_recovery)
> +		bri->prepare_recovery(adap);
> +
>  	ret = i2c_get_gpios_for_recovery(adap);
>  	if (ret)
>  		return ret;
> @@ -748,6 +757,9 @@ int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
>  	ret = i2c_generic_recovery(adap);
>  	i2c_put_gpios_for_recovery(adap);
> +	if (bri->unprepare_recovery)
> +		bri->unprepare_recovery(adap);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_generic_gpio_recovery);

That looks to like a hack made just to make things work on one platform.

I would rather wait for an answer to my query first, which I asked in a separate
email.
Vladimir Zapolskiy Sept. 29, 2016, 12:16 p.m. UTC | #2
On 09/29/2016 09:46 AM, Viresh Kumar wrote:
> On 28-09-16, 15:07, Vladimir Zapolskiy wrote:
>> I would expect that the change below improves the situation, but I didn't
>> perform any tests and here the core change is governed by the accepted
>> i.MX i2c bus driver specific changes, thus conceptually it may be incorrect:
>>
>> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
>> index da3a02ef4a31..3a4f59c3c3e6 100644
>> --- a/drivers/i2c/i2c-core.c
>> +++ b/drivers/i2c/i2c-core.c
>> @@ -697,9 +697,6 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
>>  	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
>>  	int i = 0, val = 1, ret = 0;
>> -	if (bri->prepare_recovery)
>> -		bri->prepare_recovery(adap);
>> -
>>  	bri->set_scl(adap, val);
>>  	ndelay(RECOVERY_NDELAY);
>> @@ -725,22 +722,34 @@ static int i2c_generic_recovery(struct i2c_adapter *adap)
>>  		ndelay(RECOVERY_NDELAY);
>>  	}
>> -	if (bri->unprepare_recovery)
>> -		bri->unprepare_recovery(adap);
>> -
>>  	return ret;
>>  }
>>  int i2c_generic_scl_recovery(struct i2c_adapter *adap)
>>  {
>> -	return i2c_generic_recovery(adap);
>> +	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
>> +	int ret;
>> +
>> +	if (bri->prepare_recovery)
>> +		bri->prepare_recovery(adap);
>> +
>> +	ret = i2c_generic_recovery(adap);
>> +
>> +	if (bri->unprepare_recovery)
>> +		bri->unprepare_recovery(adap);
>> +
>> +	return ret;
>>  }
>>  EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);
>>  int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
>>  {
>> +	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
>>  	int ret;
>> +	if (bri->prepare_recovery)
>> +		bri->prepare_recovery(adap);
>> +
>>  	ret = i2c_get_gpios_for_recovery(adap);
>>  	if (ret)
>>  		return ret;
>> @@ -748,6 +757,9 @@ int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
>>  	ret = i2c_generic_recovery(adap);
>>  	i2c_put_gpios_for_recovery(adap);
>> +	if (bri->unprepare_recovery)
>> +		bri->unprepare_recovery(adap);
>> +
>>  	return ret;
>>  }
>>  EXPORT_SYMBOL_GPL(i2c_generic_gpio_recovery);
>
> That looks to like a hack made just to make things work on one platform.

If you look at the top I agree that this solution may be only one platform
specific, but it fixes the broken driver of i.MX I2C bus controller.

Why do you get an impression that it looks like a hack?

> I would rather wait for an answer to my query first, which I asked in a separate
> email.
>

Why pinctrl_select_state() is not done in gpio_request_one()? Because
the first function gets pin mux/config setting and the second does not.
How do you intend to get pin mux/config setting in gpio_request_one()?

Anyway I don't see any problems in pinctrl or gpio subsystems, the bugs
must be addressed and fixed in i2c.

--
With best wishes,
Vladimir
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Viresh Kumar Sept. 30, 2016, 2:22 a.m. UTC | #3
On 29-09-16, 15:16, Vladimir Zapolskiy wrote:
> If you look at the top I agree that this solution may be only one platform
> specific, but it fixes the broken driver of i.MX I2C bus controller.

Yeah, I saw that..

> Why do you get an impression that it looks like a hack?

Because we have to reorder things to make it work on a platform. This may break
things on other platforms and we don't know about it yet.

> Why pinctrl_select_state() is not done in gpio_request_one()? Because
> the first function gets pin mux/config setting and the second does not.
> How do you intend to get pin mux/config setting in gpio_request_one()?

Lets see what Linus has to say on this..

> Anyway I don't see any problems in pinctrl or gpio subsystems, the bugs
> must be addressed and fixed in i2c.

I think it can be a gpio driver specific thing as well and not really subsystem
level one.

Patch
diff mbox

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index da3a02ef4a31..3a4f59c3c3e6 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -697,9 +697,6 @@  static int i2c_generic_recovery(struct i2c_adapter *adap)
  	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
  	int i = 0, val = 1, ret = 0;
  
-	if (bri->prepare_recovery)
-		bri->prepare_recovery(adap);
-
  	bri->set_scl(adap, val);
  	ndelay(RECOVERY_NDELAY);
  
@@ -725,22 +722,34 @@  static int i2c_generic_recovery(struct i2c_adapter *adap)
  		ndelay(RECOVERY_NDELAY);
  	}
  
-	if (bri->unprepare_recovery)
-		bri->unprepare_recovery(adap);
-
  	return ret;
  }
  
  int i2c_generic_scl_recovery(struct i2c_adapter *adap)
  {
-	return i2c_generic_recovery(adap);
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+	int ret;
+
+	if (bri->prepare_recovery)
+		bri->prepare_recovery(adap);
+
+	ret = i2c_generic_recovery(adap);
+
+	if (bri->unprepare_recovery)
+		bri->unprepare_recovery(adap);
+
+	return ret;
  }
  EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);
  
  int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
  {
+	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
  	int ret;
  
+	if (bri->prepare_recovery)
+		bri->prepare_recovery(adap);
+
  	ret = i2c_get_gpios_for_recovery(adap);
  	if (ret)
  		return ret;
@@ -748,6 +757,9 @@  int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
  	ret = i2c_generic_recovery(adap);
  	i2c_put_gpios_for_recovery(adap);
  
+	if (bri->unprepare_recovery)
+		bri->unprepare_recovery(adap);
+
  	return ret;
  }
  EXPORT_SYMBOL_GPL(i2c_generic_gpio_recovery);