Date:	Thu, 21 Oct 2010 14:20:09 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	rklein@...dia.com
CC:	broonie@...nsource.wolfsonmicro.com, cbouatmailru@...il.com,
	achew@...dia.com, olof@...om.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] power: bq24617: Adding initial charger support

Hi

rklein@...dia.com wrote:
> From: Rhyland Klein <rklein@...dia.com>
> 
> Initial checkin adding basic support for the TI BQ24617 battery charger where
> the PG output is directed to the driver via a gpio. This gpio address needs to
> be passed in the platform data to the driver.

There is not really anything specific to the BQ24617 in this driver except for the
naming. It is a driver for charger which reports its online property through a gpio
pin. I wrote a similar which I wanted to submit for 2.6.38. I'll send it as a reply
to this mail. You'll might be able to reuse it.

> 
> Signed-off-by: Rhyland Klein <rklein@...dia.com>
> ---
> Addressed comments by Mark Brown
>   * Removed dependency on TEGRA, changed to GPIO
>   * now using power_supply_changed()
>   * now using request_threaded_irq()
> 
>  drivers/power/Kconfig   |    7 ++
>  drivers/power/Makefile  |    1 +
>  drivers/power/bq24617.c |  262 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/bq24617.h |   10 ++
>  4 files changed, 280 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/power/bq24617.c
>  create mode 100644 include/linux/bq24617.h
> 
> diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
> index 60d83d9..1901ccf 100644
> --- a/drivers/power/Kconfig
> +++ b/drivers/power/Kconfig
> @@ -185,4 +185,11 @@ config CHARGER_TWL4030
>  	help
>  	  Say Y here to enable support for TWL4030 Battery Charge Interface.
>  
> +config CHARGER_BQ24617
> +	tristate "BQ24617 battery charger"
> +	depends on I2C && GENERIC_GPIO

The driver does not use any I2C functions, so it shouldn't depend on I2C

> +	help
> +	 Say Y to include support for the TI BQ24617 battery charger where PG
> +	 is attached to a gpio.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/Makefile b/drivers/power/Makefile
> index c75772e..45cd557 100644
> --- a/drivers/power/Makefile
> +++ b/drivers/power/Makefile
> @@ -32,3 +32,4 @@ obj-$(CONFIG_BATTERY_JZ4740)	+= jz4740-battery.o
>  obj-$(CONFIG_BATTERY_INTEL_MID)	+= intel_mid_battery.o
>  obj-$(CONFIG_CHARGER_ISP1704)	+= isp1704_charger.o
>  obj-$(CONFIG_CHARGER_TWL4030)	+= twl4030_charger.o
> +obj-$(CONFIG_CHARGER_BQ24617)	+= bq24617.o
> diff --git a/drivers/power/bq24617.c b/drivers/power/bq24617.c
> new file mode 100644
> index 0000000..64500e6
> --- /dev/null
> +++ b/drivers/power/bq24617.c
> @@ -0,0 +1,262 @@
> +/*
> + * Charger driver for TI's BQ24617
> + *
> + * Copyright (c) 2010, NVIDIA Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/err.h>
> +#include <linux/power_supply.h>
> +#include <linux/slab.h>
> +#include <linux/gpio.h>
> +#include <linux/bq24617.h>
> +#include <linux/interrupt.h>
> +#include <linux/platform_device.h>
> +#include <linux/irq.h>
> +
> +struct bq24617_info {
> +	struct power_supply		power_supply;
> +	struct bq24617_platform_data	*pdata;
> +	struct platform_device		*pdev;
> +	struct mutex			work_lock;
> +	struct work_struct		ac_work;
> +	int				status;
> +};
> +
> +static enum power_supply_property bq24617_properties[] = {
> +	POWER_SUPPLY_PROP_ONLINE,
> +};
> +
> +static void bq24617_batt_update(struct bq24617_info *chip)
> +{
> +	int old_status = chip->status;
> +	int new_status = old_status;
> +	struct bq24617_platform_data *pdata;
> +	int gpio_value = 0;
> +
> +	pdata = chip->pdata;
> +
> +	mutex_lock(&chip->work_lock);
> +
> +	gpio_value = gpio_get_value(pdata->gpio_addr);
> +
> +	new_status = !gpio_value;
> +	chip->status = new_status;
> +
> +	mutex_unlock(&chip->work_lock);

The mutex in its current form is quite useless since it does not protect against
anything. In my opinion it can be dropped completly. There is then a chance that
power_supply_changed is called twice although there was only one change, but that
should not cause any problems.
If you want to keep the lock you should move "old_status = chip->status" inside the
the lock (And gpio_get_value out of it).

> +
> +	if (old_status != -1 &&

If old_status is -1 it wont be equal to new_status so there is no need for an extra
check.

> +		old_status != new_status) {
> +		dev_dbg(&chip->pdev->dev,
> +			"%s: %i -> %i\n", __func__, old_status,
> +			new_status);
> +		power_supply_changed(&chip->power_supply);
> +	}
> +
> +}
> +
> +static irqreturn_t bq24617_irq_switch(int irq, void *devid)
> +{
> +	struct bq24617_info *chip = devid;
> +
> +	schedule_work(&chip->ac_work);

What Mark meant is that you should use a threaded irq so you can get rid of the
workqueue and call bq24617_batt_update directly from inside the irq handler.

> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int bq24617_get_property(struct power_supply *psy,
> +	enum power_supply_property psp,
> +	union power_supply_propval *val)
> +{
> +	struct bq24617_info *chip = container_of(psy, struct bq24617_info,
> +						power_supply);
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_ONLINE:
> +		bq24617_batt_update(chip);
> +		val->intval = chip->status;
> +		break;
> +	default:
> +		dev_err(&chip->pdev->dev,
> +			"%s: Unknown property requested.\n", __func__);
> +		return -EINVAL;
> +		break;
> +	}
> +	return 0;
> +}
> +
> +static void bq24617_ac_work(struct work_struct *work)
> +{
> +	struct bq24617_info *chip;
> +	chip = container_of(work, struct bq24617_info, ac_work);
> +	bq24617_batt_update(chip);
> +}
> +
> +static int bq24617_probe(struct platform_device *pdev)

__devinit

> +{
> +	struct bq24617_info *chip;
> +	struct bq24617_platform_data *pdata = pdev->dev.platform_data;
> +	int rc;
> +
> +	if (!pdata) {
> +		dev_err(&pdev->dev, "No platform data\n");
> +		return -ENXIO;
> +	}
> +
> +	if (!(gpio_is_valid(pdata->gpio_addr))) {
> +		dev_err(&pdev->dev, "Gpio is not valid\n");
> +		return -EINVAL;
> +	}
> +
> +	chip = kzalloc(sizeof(struct bq24617_info), GFP_KERNEL);
> +	if (!chip)
> +		return -ENOMEM;
> +
> +	chip->pdata = pdata;
> +	chip->pdev = pdev;
> +	chip->power_supply.name = "ac";
> +	chip->status = -1; /* set status to reflect unset */
> +	chip->power_supply.type = POWER_SUPPLY_TYPE_MAINS;
> +	chip->power_supply.properties = bq24617_properties;
> +	chip->power_supply.num_properties = ARRAY_SIZE(bq24617_properties);
> +	chip->power_supply.get_property = bq24617_get_property;
> +	chip->power_supply.supplied_to = pdata->batteries;
> +	chip->power_supply.num_supplicants = pdata->num_batteries;
> +
> +	mutex_init(&chip->work_lock);
> +
> +	platform_set_drvdata(pdev, chip);
> +
> +	rc = gpio_request(pdata->gpio_addr, "ac online");
> +	if (rc) {
> +		dev_err(&pdev->dev,
> +			"%s: Failed to get gpio\n", __func__);
> +		goto free_chip;
> +	}
> +
> +	gpio_direction_input(pdata->gpio_addr);
> +	if (rc) {
> +		dev_err(&pdev->dev,
> +			"%s: Failed to set gpio direction\n",
> +			__func__);
> +		goto release_gpio;
> +	}
> +
> +	rc = request_threaded_irq (gpio_to_irq(pdata->gpio_addr),
> +				NULL,
> +				bq24617_irq_switch,
> +				IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
> +				"ac detect",
> +				chip);
> +
> +	if (rc) {
> +		dev_err(&pdev->dev,
> +			"%s: Failed to request threaded IRQ\n", __func__);
> +		goto release_gpio;
> +	}
> +
> +	INIT_WORK(&chip->ac_work, bq24617_ac_work);

In theory the irq can fire before the work_struct has been initalised.

> +
> +	rc = power_supply_register(&pdev->dev, &chip->power_supply);
> +	if (rc) {
> +		dev_err(&pdev->dev,
> +			"%s: Failed to register power supply\n", __func__);
> +		goto free_irq;
> +	}
> +
> +	dev_info(&pdev->dev,
> +		"%s: battery charger ac device registered\n", pdev->name);
> +
> +	schedule_work(&chip->ac_work);
> +
> +	return 0;
> +
> +free_irq:
> +	free_irq(gpio_to_irq(pdata->gpio_addr), chip);
> +release_gpio:
> +	gpio_free(pdata->gpio_addr);
> +free_chip:
> +	kfree(chip);
> +	return rc;
> +}
> +
> +static int bq24617_remove(struct platform_device *pdev)

__devexit

> +{
> +	struct bq24617_info *chip = platform_get_drvdata(pdev);
> +	struct bq24617_platform_data *pdata = chip->pdata;
> +
> +	flush_scheduled_work();
> +
> +	power_supply_unregister(&chip->power_supply);
> +
> +	free_irq(gpio_to_irq(pdata->gpio_addr), chip);
> +	gpio_free(pdata->gpio_addr);
> +	kfree(chip);
> +
> +	return 0;
> +}
> +
> +#if CONFIG_PM
> +static int bq24617_suspend(struct platform_device *pdev, pm_message_t state)
> +{
> +	flush_scheduled_work();
> +
> +	return 0;
> +}
> +
> +static int bq24617_resume(struct platform_device *pdev)
> +{
> +	struct bq24617_info *chip = platform_get_drvdata(pdev);
> +
> +	schedule_work(&chip->ac_work);
> +
> +	return 0;
> +}
> +
> +#else
> +#define bq24617_suspend         NULL
> +#define bq24617_resume          NULL
> +#endif
> +
> +static struct platform_driver bq24617_driver = {
> +	.driver = {
> +		.name	= "bq24617",
> +		.owner	= THIS_MODULE,
> +	},
> +	.probe		= bq24617_probe,
> +	.remove		= __devexit_p(bq24617_remove),
> +	.suspend	= bq24617_suspend,
> +	.resume		= bq24617_resume,
> +};
> +
> +static int __devinit bq24617_init(void)

__init

> +{
> +	return platform_driver_register(&bq24617_driver);
> +}
> +module_init(bq24617_init);
> +
> +static void __devexit bq24617_exit(void)

__exit

> +{
> +	platform_driver_unregister(&bq24617_driver);
> +}
> +module_exit(bq24617_exit);
> +
> +MODULE_AUTHOR("Rhyland Klein <rklein@...dia.com");
> +MODULE_DESCRIPTION("BQ24617 battery charger driver");
> +MODULE_LICENSE("GPL");


- Lars

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