Message-ID: <20160525212659.GK26360@valkosipuli.retiisi.org.uk>
Date:	Thu, 26 May 2016 00:26:59 +0300
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Pavel Machek <pavel@....cz>
Cc:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	pali.rohar@...il.com, sre@...nel.org,
	kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, patrikbachan@...il.com, serge@...lyn.com,
	linux-media@...r.kernel.org, mchehab@....samsung.com
Subject: Re: [PATCHv4] support for AD5820 camera auto-focus coil

Hi Pavel,

Thanks for your continued work on this! :-)

Some quite minor comments below. I think we're good then.

On Tue, May 24, 2016 at 11:17:46AM +0200, Pavel Machek wrote:
> This adds support for AD5820 autofocus coil, found for example in
> Nokia N900 smartphone.
> 
> Signed-off-by: Pavel Machek <pavel@....cz>
> 
> ---
> v2: simple cleanups, fix error paths, simplify probe
> v3: more cleanups, remove printk, add include
> v4: remove header file.
> 
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 993dc50..77313a1 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -279,6 +279,13 @@ config VIDEO_ML86V7667
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ml86v7667.
>  
> +config VIDEO_AD5820
> +	tristate "AD5820 lens voice coil support"
> +	depends on I2C && VIDEO_V4L2 && MEDIA_CONTROLLER
> +	---help---
> +	  This is a driver for the AD5820 camera lens voice coil.
> +	  It is used for example in Nokia N900 (RX-51).
> +
>  config VIDEO_SAA7110
>  	tristate "Philips SAA7110 video decoder"
>  	depends on VIDEO_V4L2 && I2C
> diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
> index 94f2c99..34434ae 100644
> --- a/drivers/media/i2c/Makefile
> +++ b/drivers/media/i2c/Makefile
> @@ -19,6 +20,7 @@ obj-$(CONFIG_VIDEO_SAA717X) += saa717x.o
>  obj-$(CONFIG_VIDEO_SAA7127) += saa7127.o
>  obj-$(CONFIG_VIDEO_SAA7185) += saa7185.o
>  obj-$(CONFIG_VIDEO_SAA6752HS) += saa6752hs.o
> +obj-$(CONFIG_VIDEO_AD5820)  += ad5820.o
>  obj-$(CONFIG_VIDEO_ADV7170) += adv7170.o
>  obj-$(CONFIG_VIDEO_ADV7175) += adv7175.o
>  obj-$(CONFIG_VIDEO_ADV7180) += adv7180.o
> diff --git a/drivers/media/i2c/ad5820.c b/drivers/media/i2c/ad5820.c
> new file mode 100644
> index 0000000..f956bd3
> --- /dev/null
> +++ b/drivers/media/i2c/ad5820.c
> @@ -0,0 +1,438 @@
> +/*
> + * drivers/media/i2c/ad5820.c
> + *
> + * AD5820 DAC driver for camera voice coil focus.
> + *
> + * Copyright (C) 2008 Nokia Corporation
> + * Copyright (C) 2007 Texas Instruments
> + * Copyright (C) 2016 Pavel Machek <pavel@....cz>
> + *
> + * Contact: Tuukka Toivonen
> + *          Sakari Ailus

Could you put the e-mail addresses back, please?

Tuukka's e-mail is tuukkat76 at gmail.com .

> + *
> + * Based on af_d88.c by Texas Instruments.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + *
> + * 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.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/regulator/consumer.h>

Alphabetical order would be nice. The same below.

> +
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-subdev.h>
> +
> +#define AD5820_NAME		"ad5820"
> +
> +/* Register definitions */
> +#define AD5820_POWER_DOWN		(1 << 15)
> +#define AD5820_DAC_SHIFT		4
> +#define AD5820_RAMP_MODE_LINEAR		(0 << 3)
> +#define AD5820_RAMP_MODE_64_16		(1 << 3)
> +
> +#define CODE_TO_RAMP_US(s)	((s) == 0 ? 0 : (1 << ((s) - 1)) * 50)
> +#define RAMP_US_TO_CODE(c)	fls(((c) + ((c)>>1)) / 50)
> +
> +#define to_ad5820_device(sd)	container_of(sd, struct ad5820_device, subdev)
> +
> +struct ad5820_device {
> +	struct v4l2_subdev subdev;
> +	struct ad5820_platform_data *platform_data;
> +	struct regulator *vana;
> +
> +	struct v4l2_ctrl_handler ctrls;
> +	u32 focus_absolute;
> +	u32 focus_ramp_time;
> +	u32 focus_ramp_mode;
> +
> +	struct mutex power_lock;
> +	int power_count;
> +
> +	int standby : 1;
> +};
> +
> +/**
> + * @brief I2C write using i2c_transfer().
> + * @param coil - the driver data structure
> + * @param data - register value to be written

This does not look entirely right. But you could just remove the entire
comment. It's useless.

> + * @returns nonnegative on success, negative if failed
> + */
> +static int ad5820_write(struct ad5820_device *coil, u16 data)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(&coil->subdev);
> +	struct i2c_msg msg;
> +	int r;
> +
> +	if (!client->adapter)
> +		return -ENODEV;
> +
> +	data = cpu_to_be16(data);
> +	msg.addr  = client->addr;
> +	msg.flags = 0;
> +	msg.len   = 2;
> +	msg.buf   = (u8 *)&data;
> +
> +	r = i2c_transfer(client->adapter, &msg, 1);
> +	if (r < 0) {
> +		dev_err(&client->dev, "write failed, error %d\n", r);
> +		return r;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Calculate status word and write it to the device based on current
> + * values of V4L2 controls. It is assumed that the stored V4L2 control
> + * values are properly limited and rounded.
> + */
> +static int ad5820_update_hw(struct ad5820_device *coil)
> +{
> +	u16 status;
> +
> +	status = RAMP_US_TO_CODE(coil->focus_ramp_time);
> +	status |= coil->focus_ramp_mode
> +		? AD5820_RAMP_MODE_64_16 : AD5820_RAMP_MODE_LINEAR;
> +	status |= coil->focus_absolute << AD5820_DAC_SHIFT;
> +
> +	if (coil->standby)
> +		status |= AD5820_POWER_DOWN;
> +
> +	return ad5820_write(coil, status);
> +}
> +
> +/*
> + * Power handling
> + */
> +static int ad5820_power_off(struct ad5820_device *coil, int standby)
> +{
> +	int ret = 0;
> +
> +	/*
> +	 * Go to standby first as real power off my be denied by the hardware
> +	 * (single power line control for both coil and sensor).
> +	 */
> +	if (standby) {
> +		coil->standby = 1;
> +		ret = ad5820_update_hw(coil);
> +	}
> +
> +	ret |= regulator_disable(coil->vana);

This is actually an error code and you shouldn't use or to combine two error
codes. The result will make no sense.

It might be the driver did this in the past but it should not be done. The
right thing, as elsewhere, is to assign the value to ret and check it. The
assigment in declaration may be dropped as well.

I think this happens in a few places in the driver.

> +
> +	return ret;
> +}
> +
> +static int ad5820_power_on(struct ad5820_device *coil, int restore)
> +{
> +	int ret;
> +
> +	ret = regulator_enable(coil->vana);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (restore) {
> +		/* Restore the hardware settings. */
> +		coil->standby = 0;
> +		ret = ad5820_update_hw(coil);
> +		if (ret)
> +			goto fail;
> +	}
> +	return 0;
> +
> +fail:
> +	coil->standby = 1;
> +	regulator_disable(coil->vana);
> +
> +	return ret;
> +}
> +
> +/*
> + * V4L2 controls
> + */
> +static int ad5820_set_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +	struct ad5820_device *coil =
> +		container_of(ctrl->handler, struct ad5820_device, ctrls);
> +	u32 code;
> +
> +	switch (ctrl->id) {
> +	case V4L2_CID_FOCUS_ABSOLUTE:
> +		coil->focus_absolute = ctrl->val;
> +		return ad5820_update_hw(coil);
> +
> +	case V4L2_CID_FOCUS_AD5820_RAMP_TIME:
> +		code = RAMP_US_TO_CODE(ctrl->val);
> +		ctrl->val = CODE_TO_RAMP_US(code);
> +		coil->focus_ramp_time = ctrl->val;
> +		break;
> +
> +	case V4L2_CID_FOCUS_AD5820_RAMP_MODE:
> +		coil->focus_ramp_mode = ctrl->val;
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct v4l2_ctrl_ops ad5820_ctrl_ops = {
> +	.s_ctrl = ad5820_set_ctrl,
> +};
> +
> +static const char * const ad5820_focus_menu[] = {
> +	"Linear ramp",
> +	"64/16 ramp",
> +};
> +
> +static const struct v4l2_ctrl_config ad5820_ctrls[] = {
> +	{
> +		.ops		= &ad5820_ctrl_ops,
> +		.id		= V4L2_CID_FOCUS_AD5820_RAMP_TIME,
> +		.type		= V4L2_CTRL_TYPE_INTEGER,
> +		.name		= "Focus ramping time [us]",
> +		.min		= 0,
> +		.max		= 3200,
> +		.step		= 50,
> +		.def		= 0,
> +		.flags		= 0,
> +	},
> +	{
> +		.ops		= &ad5820_ctrl_ops,
> +		.id		= V4L2_CID_FOCUS_AD5820_RAMP_MODE,
> +		.type		= V4L2_CTRL_TYPE_MENU,
> +		.name		= "Focus ramping mode",
> +		.min		= 0,
> +		.max		= ARRAY_SIZE(ad5820_focus_menu),
> +		.step		= 0,
> +		.def		= 0,
> +		.flags		= 0,
> +		.qmenu		= ad5820_focus_menu,
> +	},
> +};
> +
> +
> +static int ad5820_init_controls(struct ad5820_device *coil)
> +{
> +	unsigned int i;
> +
> +	v4l2_ctrl_handler_init(&coil->ctrls, ARRAY_SIZE(ad5820_ctrls) + 1);
> +
> +	/*
> +	 * V4L2_CID_FOCUS_ABSOLUTE
> +	 *
> +	 * Minimum current is 0 mA, maximum is 100 mA. Thus, 1 code is
> +	 * equivalent to 100/1023 = 0.0978 mA. Nevertheless, we do not use [mA]
> +	 * for focus position, because it is meaningless for user. Meaningful
> +	 * would be to use focus distance or even its inverse, but since the
> +	 * driver doesn't have sufficiently knowledge to do the conversion, we
> +	 * will just use abstract codes here. In any case, smaller value = focus
> +	 * position farther from camera. The default zero value means focus at
> +	 * infinity, and also least current consumption.
> +	 */
> +	v4l2_ctrl_new_std(&coil->ctrls, &ad5820_ctrl_ops,
> +			  V4L2_CID_FOCUS_ABSOLUTE, 0, 1023, 1, 0);
> +
> +	/* V4L2_CID_TEST_PATTERN and V4L2_CID_MODE_* */
> +	for (i = 0; i < ARRAY_SIZE(ad5820_ctrls); ++i)
> +		v4l2_ctrl_new_custom(&coil->ctrls, &ad5820_ctrls[i], NULL);
> +
> +	if (coil->ctrls.error)
> +		return coil->ctrls.error;
> +
> +	coil->focus_absolute = 0;
> +	coil->focus_ramp_time = 0;
> +	coil->focus_ramp_mode = 0;
> +
> +	coil->subdev.ctrl_handler = &coil->ctrls;
> +
> +	return 0;
> +}
> +
> +/*
> + * V4L2 subdev operations
> + */
> +static int ad5820_registered(struct v4l2_subdev *subdev)
> +{
> +	struct ad5820_device *coil = to_ad5820_device(subdev);
> +	struct i2c_client *client = v4l2_get_subdevdata(subdev);
> +
> +	coil->vana = regulator_get(&client->dev, "VANA");

Is there a reason not to acquire this in probe instead?

> +	if (IS_ERR(coil->vana)) {
> +		dev_err(&client->dev, "could not get regulator for vana\n");
> +		return -ENODEV;

I wonder if -EPROBE_DEFER might be the right error code here.

> +	}
> +
> +	return ad5820_init_controls(coil);
> +}
> +
> +static int
> +ad5820_set_power(struct v4l2_subdev *subdev, int on)
> +{
> +	struct ad5820_device *coil = to_ad5820_device(subdev);
> +	int ret = 0;
> +
> +	mutex_lock(&coil->power_lock);
> +
> +	/*
> +	 * If the power count is modified from 0 to != 0 or from != 0 to 0,
> +	 * update the power state.
> +	 */
> +	if (coil->power_count == !on) {
> +		ret = on ? ad5820_power_on(coil, 1) : ad5820_power_off(coil, 1);
> +		if (ret < 0)
> +			goto done;
> +	}
> +
> +	/* Update the power count. */
> +	coil->power_count += on ? 1 : -1;
> +	WARN_ON(coil->power_count < 0);
> +
> +done:
> +	mutex_unlock(&coil->power_lock);
> +	return ret;
> +}
> +
> +static int ad5820_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> +{
> +	return ad5820_set_power(sd, 1);
> +}
> +
> +static int ad5820_close(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
> +{
> +	return ad5820_set_power(sd, 0);
> +}
> +
> +static const struct v4l2_subdev_core_ops ad5820_core_ops = {
> +	.s_power = ad5820_set_power,
> +};
> +
> +static const struct v4l2_subdev_ops ad5820_ops = {
> +	.core = &ad5820_core_ops,
> +};
> +
> +static const struct v4l2_subdev_internal_ops ad5820_internal_ops = {
> +	.registered = ad5820_registered,
> +	.open = ad5820_open,
> +	.close = ad5820_close,
> +};
> +
> +/*
> + * I2C driver
> + */
> +#ifdef CONFIG_PM
> +
> +static int ad5820_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
> +	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
> +	struct ad5820_device *coil = to_ad5820_device(subdev);
> +
> +	if (!coil->power_count)
> +		return 0;
> +
> +	return ad5820_power_off(coil, 0);
> +}
> +
> +static int ad5820_resume(struct device *dev)
> +{
> +	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
> +	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
> +	struct ad5820_device *coil = to_ad5820_device(subdev);
> +
> +	if (!coil->power_count)
> +		return 0;
> +
> +	return ad5820_power_on(coil, 1);
> +}
> +
> +#else
> +
> +#define ad5820_suspend	NULL
> +#define ad5820_resume	NULL
> +
> +#endif /* CONFIG_PM */
> +
> +static int ad5820_probe(struct i2c_client *client,
> +			const struct i2c_device_id *devid)
> +{
> +	struct ad5820_device *coil;
> +	int ret = 0;

No need to assign ret here.

> +
> +	coil = kzalloc(sizeof(*coil), GFP_KERNEL);

You could use devm_kzalloc() here and drop kfree() below and in _remove().

The driver might be actually older than the devm_*() functions. Not sure. At
least they were not widely used back then. :-)

> +	if (!coil)
> +		return -ENOMEM;
> +
> +	mutex_init(&coil->power_lock);
> +
> +	v4l2_i2c_subdev_init(&coil->subdev, client, &ad5820_ops);
> +	coil->subdev.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> +	coil->subdev.internal_ops = &ad5820_internal_ops;
> +	strcpy(coil->subdev.name, "ad5820 focus");
> +
> +	ret = media_entity_pads_init(&coil->subdev.entity, 0, NULL);
> +	if (ret < 0)
> +		goto free;
> +
> +	ret = v4l2_async_register_subdev(&coil->subdev);
> +	if (ret < 0)
> +		goto cleanup;
> +
> +	return ret;
> +
> +cleanup:
> +	media_entity_cleanup(&coil->subdev.entity);
> +
> +free:
> +	kfree(coil);
> +
> +	return ret;
> +}
> +
> +static int __exit ad5820_remove(struct i2c_client *client)
> +{
> +	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
> +	struct ad5820_device *coil = to_ad5820_device(subdev);
> +
> +	v4l2_device_unregister_subdev(&coil->subdev);
> +	v4l2_ctrl_handler_free(&coil->ctrls);
> +	media_entity_cleanup(&coil->subdev.entity);
> +	if (coil->vana)
> +		regulator_put(coil->vana);

mutex_destroy(&coil->power_lock);

Here. And in probe() error paths as well.

> +
> +	kfree(coil);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ad5820_id_table[] = {
> +	{ AD5820_NAME, 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ad5820_id_table);
> +
> +static SIMPLE_DEV_PM_OPS(ad5820_pm, ad5820_suspend, ad5820_resume);
> +
> +static struct i2c_driver ad5820_i2c_driver = {
> +	.driver		= {
> +		.name	= AD5820_NAME,
> +		.pm	= &ad5820_pm,
> +	},
> +	.probe		= ad5820_probe,
> +	.remove		= __exit_p(ad5820_remove),
> +	.id_table	= ad5820_id_table,
> +};
> +
> +module_i2c_driver(ad5820_i2c_driver);
> +
> +MODULE_AUTHOR("Tuukka Toivonen");
> +MODULE_DESCRIPTION("AD5820 camera lens driver");
> +MODULE_LICENSE("GPL");

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk

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