Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

[Sebastian Reichel]

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[of course I forgot to actually add gpio people, let's try again]

On Wed, Dec 14, 2016 at 05:59:21PM +0100, Sebastian Reichel wrote:
> Hi,
> 
> On Wed, Dec 14, 2016 at 12:56:45AM +0100, Peter Rosin wrote:
> > If several parallel bq24735 chargers have their ac-detect gpios wired
> > together (or if only one of the parallel bq24735 chargers have its
> > ac-detect pin wired to a gpio, and the others are assumed to react the
> > same), then all driver instances need to check the same gpio. But the
> > gpio subsystem does not allow sharing gpios, so handle that locally.
> 
> Adding GPIO subsystem people to see if they can come up with
> something in the gpiod API for this usecase.
> 
> > However, only do this for the polling case, sharing is not supported if
> > the ac detection is handled with interrupts.
> 
> Why? I guess you only added the gpio polling stuff for the shared
> gpio feature, so we can skip the gpio polling if we add shared irq
> support instead?
> 
> > Signed-off-by: Peter Rosin <peda@axentia.se>
> > ---
> >  drivers/power/supply/bq24735-charger.c | 111 +++++++++++++++++++++++++++++----
> >  1 file changed, 100 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/power/supply/bq24735-charger.c b/drivers/power/supply/bq24735-charger.c
> > index f45876927676..c2403c4d5ece 100644
> > --- a/drivers/power/supply/bq24735-charger.c
> > +++ b/drivers/power/supply/bq24735-charger.c
> > @@ -25,6 +25,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> > +#include <linux/of_gpio.h>
> >  #include <linux/gpio/consumer.h>
> >  #include <linux/power_supply.h>
> >  #include <linux/slab.h>
> > @@ -43,12 +44,24 @@
> >  #define BQ24735_MANUFACTURER_ID		0xfe
> >  #define BQ24735_DEVICE_ID		0xff
> >  
> > +struct bq24735;
> > +
> > +struct bq24735_shared {
> > +	struct list_head		list;
> > +	struct bq24735			*owner;
> > +	struct gpio_desc		*status_gpio;
> > +};
> > +
> > +static DEFINE_MUTEX(shared_lock);
> > +static LIST_HEAD(shared_list);
> > +
> >  struct bq24735 {
> >  	struct power_supply		*charger;
> >  	struct power_supply_desc	charger_desc;
> >  	struct i2c_client		*client;
> >  	struct bq24735_platform		*pdata;
> >  	struct mutex			lock;
> > +	struct bq24735_shared		*shared;
> >  	struct gpio_desc		*status_gpio;
> >  	struct delayed_work		poll;
> >  	u32				poll_interval;
> > @@ -346,6 +359,75 @@ static struct bq24735_platform *bq24735_parse_dt_data(struct i2c_client *client)
> >  	return pdata;
> >  }
> >  
> > +static struct gpio_desc *bq24735_get_status_gpio(struct bq24735 *charger)
> > +{
> > +	struct device *dev = &charger->client->dev;
> > +	struct bq24735_shared *shared;
> > +	int gpio;
> > +	enum of_gpio_flags flags;
> > +	int active_low;
> > +	struct list_head *pos;
> > +
> > +	if (of_property_read_bool(dev->of_node, "ti,ac-detect-gpios"))
> > +		gpio = of_get_named_gpio_flags(dev->of_node,
> > +					       "ti,ac-detect-gpios", 0, &flags);
> > +	else if (of_property_read_bool(dev->of_node, "ti,ac-detect-gpio"))
> > +		gpio = of_get_named_gpio_flags(dev->of_node,
> > +					       "ti,ac-detect-gpio", 0, &flags);
> > +	else
> > +		return NULL;
> > +
> > +	if (!gpio_is_valid(gpio))
> > +		return ERR_PTR(gpio);
> > +	active_low = flags & OF_GPIO_ACTIVE_LOW;
> > +
> > +	mutex_lock(&shared_lock);
> > +	list_for_each(pos, &shared_list) {
> > +		shared = list_entry(pos, struct bq24735_shared, list);
> > +		if (gpio != desc_to_gpio(shared->status_gpio))
> > +			continue;
> > +		if (!active_low ^ !gpiod_is_active_low(shared->status_gpio))
> > +			continue;
> > +
> > +		get_device(&shared->owner->client->dev);
> > +		dev_dbg(dev, "sharing gpio with %s\n",
> > +			shared->owner->pdata->name);
> > +		charger->shared = shared;
> > +		mutex_unlock(&shared_lock);
> > +		return shared->status_gpio;
> > +	}
> > +
> > +	shared = devm_kzalloc(dev, sizeof(*shared), GFP_KERNEL);
> > +	if (!shared) {
> > +		mutex_unlock(&shared_lock);
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +	shared->owner = charger;
> > +	shared->status_gpio = gpiod_get(dev, "ti,ac-detect", GPIOD_IN);
> > +	if (!IS_ERR(shared->status_gpio)) {
> > +		charger->shared = shared;
> > +		list_add(&shared->list, &shared_list);
> > +	}
> > +	mutex_unlock(&shared_lock);
> > +
> > +	return shared->status_gpio;
> > +}
> > +
> > +static void bq24735_put_status_gpio(struct bq24735 *charger)
> > +{
> > +	if (!charger->shared)
> > +		return;
> > +
> > +	mutex_lock(&shared_lock);
> > +	if (charger->shared->owner != charger) {
> > +		put_device(&charger->shared->owner->client->dev);
> > +	} else {
> > +		list_del(&charger->shared->list);
> > +		gpiod_put(charger->shared->status_gpio);
> > +	}
> > +	mutex_unlock(&shared_lock);
> > +}
> > +
> >  static int bq24735_charger_probe(struct i2c_client *client,
> >  				 const struct i2c_device_id *id)
> >  {
> > @@ -402,9 +484,7 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  
> >  	i2c_set_clientdata(client, charger);
> >  
> > -	charger->status_gpio = devm_gpiod_get_optional(&client->dev,
> > -						       "ti,ac-detect",
> > -						       GPIOD_IN);
> > +	charger->status_gpio = bq24735_get_status_gpio(charger);
> >  	if (IS_ERR(charger->status_gpio)) {
> >  		ret = PTR_ERR(charger->status_gpio);
> >  		dev_err(&client->dev, "Getting gpio failed: %d\n", ret);
> > @@ -416,28 +496,30 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  		if (ret < 0) {
> >  			dev_err(&client->dev, "Failed to read manufacturer id : %d\n",
> >  				ret);
> > -			return ret;
> > +			goto out;
> >  		} else if (ret != 0x0040) {
> >  			dev_err(&client->dev,
> >  				"manufacturer id mismatch. 0x0040 != 0x%04x\n", ret);
> > -			return -ENODEV;
> > +			ret = -ENODEV;
> > +			goto out;
> >  		}
> >  
> >  		ret = bq24735_read_word(client, BQ24735_DEVICE_ID);
> >  		if (ret < 0) {
> >  			dev_err(&client->dev, "Failed to read device id : %d\n", ret);
> > -			return ret;
> > +			goto out;
> >  		} else if (ret != 0x000B) {
> >  			dev_err(&client->dev,
> >  				"device id mismatch. 0x000b != 0x%04x\n", ret);
> > -			return -ENODEV;
> > +			ret = -ENODEV;
> > +			goto out;
> >  		}
> >  	}
> >  
> >  	ret = bq24735_config_charger(charger);
> >  	if (ret < 0) {
> >  		dev_err(&client->dev, "failed in configuring charger");
> > -		return ret;
> > +		goto out;
> >  	}
> >  
> >  	/* check for AC adapter presence */
> > @@ -445,7 +527,7 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  		ret = bq24735_enable_charging(charger);
> >  		if (ret < 0) {
> >  			dev_err(&client->dev, "Failed to enable charging\n");
> > -			return ret;
> > +			goto out;
> >  		}
> >  	}
> >  
> > @@ -455,7 +537,7 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  		ret = PTR_ERR(charger->charger);
> >  		dev_err(&client->dev, "Failed to register power supply: %d\n",
> >  			ret);
> > -		return ret;
> > +		goto out;
> >  	}
> >  
> >  	if (client->irq) {
> > @@ -470,7 +552,7 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  			dev_err(&client->dev,
> >  				"Unable to register IRQ %d err %d\n",
> >  				client->irq, ret);
> > -			return ret;
> > +			goto out;
> >  		}
> >  	} else if (charger->status_gpio) {
> >  		ret = of_property_read_u32(client->dev.of_node,
> > @@ -487,6 +569,11 @@ static int bq24735_charger_probe(struct i2c_client *client,
> >  	}
> >  
> >  	return 0;
> > +
> > +out:
> > +	bq24735_put_status_gpio(charger);
> > +
> > +	return ret;
> >  }
> >  
> >  static int bq24735_charger_remove(struct i2c_client *client)
> > @@ -496,6 +583,8 @@ static int bq24735_charger_remove(struct i2c_client *client)
> >  	if (charger->poll_interval)
> >  		cancel_delayed_work_sync(&charger->poll);
> >  
> > +	bq24735_put_status_gpio(charger);
> > +
> >  	return 0;
> >  }
> >  
> > -- 
> > 2.1.4
> > 



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Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

[Peter Rosin]

On 2016-12-14 18:01, Sebastian Reichel wrote:
> [of course I forgot to actually add gpio people, let's try again]
> 
> On Wed, Dec 14, 2016 at 05:59:21PM +0100, Sebastian Reichel wrote:
>> Hi,
>>
>> On Wed, Dec 14, 2016 at 12:56:45AM +0100, Peter Rosin wrote:
>>> If several parallel bq24735 chargers have their ac-detect gpios wired
>>> together (or if only one of the parallel bq24735 chargers have its
>>> ac-detect pin wired to a gpio, and the others are assumed to react the
>>> same), then all driver instances need to check the same gpio. But the
>>> gpio subsystem does not allow sharing gpios, so handle that locally.
>>
>> Adding GPIO subsystem people to see if they can come up with
>> something in the gpiod API for this usecase.

Right, I don't like how my new code steps away from gpio descriptors.

>>> However, only do this for the polling case, sharing is not supported if
>>> the ac detection is handled with interrupts.
>>
>> Why? I guess you only added the gpio polling stuff for the shared
>> gpio feature, so we can skip the gpio polling if we add shared irq
>> support instead?

Nope, the hw really can't do interrupts on the gpio, it's just not wired
up for that. The gpio is on an expander, and the irq line from the expander
top the cpu is not there (due to a desire to minimize the number of
connections between two parts of the system). So I need both polling and
sharing.

Cheers,
peda

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Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

[Linus Walleij]

On Wed, Dec 14, 2016 at 6:41 PM, Peter Rosin <peda@axentia.se> wrote:
> On 2016-12-14 18:01, Sebastian Reichel wrote:
>> [of course I forgot to actually add gpio people, let's try again]
>>
>> On Wed, Dec 14, 2016 at 05:59:21PM +0100, Sebastian Reichel wrote:
>>> Hi,
>>>
>>> On Wed, Dec 14, 2016 at 12:56:45AM +0100, Peter Rosin wrote:
>>>> If several parallel bq24735 chargers have their ac-detect gpios wired
>>>> together (or if only one of the parallel bq24735 chargers have its
>>>> ac-detect pin wired to a gpio, and the others are assumed to react the
>>>> same), then all driver instances need to check the same gpio. But the
>>>> gpio subsystem does not allow sharing gpios, so handle that locally.
>>>
>>> Adding GPIO subsystem people to see if they can come up with
>>> something in the gpiod API for this usecase.
>
> Right, I don't like how my new code steps away from gpio descriptors.

The issue of shared gpiods have come up over and over again.
For example the messy regulator code needs this too.

It is better if we implement something like gpiod_get_shared()
in the gpiolib of these cases.

Just put a refcount in struct gpio_desc in drivers/gpio/gpiolib.h
for this case I guess?

Yours,
Linus Walleij

Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

[Peter Rosin]

On 2016-12-30 08:49, Linus Walleij wrote:
> On Wed, Dec 14, 2016 at 6:41 PM, Peter Rosin <peda@axentia.se> wrote:
>> On 2016-12-14 18:01, Sebastian Reichel wrote:
>>> [of course I forgot to actually add gpio people, let's try again]
>>>
>>> On Wed, Dec 14, 2016 at 05:59:21PM +0100, Sebastian Reichel wrote:
>>>> Hi,
>>>>
>>>> On Wed, Dec 14, 2016 at 12:56:45AM +0100, Peter Rosin wrote:
>>>>> If several parallel bq24735 chargers have their ac-detect gpios wired
>>>>> together (or if only one of the parallel bq24735 chargers have its
>>>>> ac-detect pin wired to a gpio, and the others are assumed to react the
>>>>> same), then all driver instances need to check the same gpio. But the
>>>>> gpio subsystem does not allow sharing gpios, so handle that locally.
>>>>
>>>> Adding GPIO subsystem people to see if they can come up with
>>>> something in the gpiod API for this usecase.
>>
>> Right, I don't like how my new code steps away from gpio descriptors.
> 
> The issue of shared gpiods have come up over and over again.
> For example the messy regulator code needs this too.
> 
> It is better if we implement something like gpiod_get_shared()
> in the gpiolib of these cases.
> 
> Just put a refcount in struct gpio_desc in drivers/gpio/gpiolib.h
> for this case I guess?

I actually tried that, but ran into atomicy issues with the
FLAG_REQUESTED bit and gave up. Didn't really try all that hard
though, but I simply didn't feel comfortable with going near such
fundamental designs...

Cheers,
peda

Re: [PATCH v2 3/3] power: supply: bq24735-charger: allow chargers to share the ac-detect gpio

[Linus Walleij]

On Mon, Jan 2, 2017 at 9:31 AM, Peter Rosin <peda@axentia.se> wrote:
> On 2016-12-30 08:49, Linus Walleij wrote:
>> On Wed, Dec 14, 2016 at 6:41 PM, Peter Rosin <peda@axentia.se> wrote:
>>> On 2016-12-14 18:01, Sebastian Reichel wrote:
>>>> [of course I forgot to actually add gpio people, let's try again]
>>>>
>>>> On Wed, Dec 14, 2016 at 05:59:21PM +0100, Sebastian Reichel wrote:
>>>>> Hi,
>>>>>
>>>>> On Wed, Dec 14, 2016 at 12:56:45AM +0100, Peter Rosin wrote:
>>>>>> If several parallel bq24735 chargers have their ac-detect gpios wired
>>>>>> together (or if only one of the parallel bq24735 chargers have its
>>>>>> ac-detect pin wired to a gpio, and the others are assumed to react the
>>>>>> same), then all driver instances need to check the same gpio. But the
>>>>>> gpio subsystem does not allow sharing gpios, so handle that locally.
>>>>>
>>>>> Adding GPIO subsystem people to see if they can come up with
>>>>> something in the gpiod API for this usecase.
>>>
>>> Right, I don't like how my new code steps away from gpio descriptors.
>>
>> The issue of shared gpiods have come up over and over again.
>> For example the messy regulator code needs this too.
>>
>> It is better if we implement something like gpiod_get_shared()
>> in the gpiolib of these cases.
>>
>> Just put a refcount in struct gpio_desc in drivers/gpio/gpiolib.h
>> for this case I guess?
>
> I actually tried that, but ran into atomicy issues with the
> FLAG_REQUESTED bit and gave up. Didn't really try all that hard
> though, but I simply didn't feel comfortable with going near such
> fundamental designs...

Oh I see. Well if it is of any help that would make me nervous too.

I would just remove the use of FLAG_REQUESTED altogether,
redefine the flags in gpiolib.h from 0 and add a struct kref into the struct
to deal with the refcounting.

That should do it. I think.

Yours,
Linus Walleij