Message-ID: <CAHfPSqDWRU6Jjnhjx-8=Ps_2G3KRok8_+aNSMcvtA+rFTDE2Yw@mail.gmail.com>
Date:	Tue, 22 Jan 2013 19:33:00 +0530
From:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, dianders@...omium.org,
	gregkh@...uxfoundation.org
Subject: Re: [PATCH] iio: adc: add exynos5 adc driver under iio framwork

Hello All,

On 22 January 2013 15:14, Lars-Peter Clausen <lars@...afoo.de> wrote:
>
> Hi,
>
> On 01/21/2013 02:37 PM, Naveen Krishna Chatradhi wrote:
> > This patch add an ADC IP found on EXYNOS5 series socs from Samsung.
> > Also adds the Documentation for device tree bindings.
> >[...]
> > diff --git a/drivers/iio/adc/exynos5_adc.c
> > b/drivers/iio/adc/exynos5_adc.c
> > new file mode 100644
> > index 0000000..cd33ea2
> > --- /dev/null
> > +++ b/drivers/iio/adc/exynos5_adc.c
> > @@ -0,0 +1,412 @@
> > +/*
> > + *  exynos5_adc.c - Support for ADC in EXYNOS5 SoCs
> > + *
> > + *  8-channel, 10/12-bit ADC
> > + *
> > + *  Copyright (C) 2013 Naveen Krishna Chatradhi <ch.naveen@...sung.com>
> > + *
> > + *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/delay.h>
> > +#include <linux/kernel.h>
> > +#include <linux/slab.h>
> > +#include <linux/io.h>
> > +#include <linux/clk.h>
> > +#include <linux/completion.h>
> > +#include <linux/of.h>
> > +#include <linux/of_irq.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/of_platform.h>
> > +
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/machine.h>
> > +#include <linux/iio/driver.h>
> > +
> > +/* Samsung ADC registers definitions */
> > +#define EXYNOS_ADC_CON(x)    ((x) + 0x00)
> > +#define EXYNOS_ADC_DLY(x)    ((x) + 0x08)
> > +#define EXYNOS_ADC_DATX(x)   ((x) + 0x0C)
> > +#define EXYNOS_ADC_INTCLR(x) ((x) + 0x18)
> > +#define EXYNOS_ADC_MUX(x)    ((x) + 0x1c)
> > +
> > +/* Bit definitions for EXYNOS_ADC_MUX: */
> > +#define ADC_RES              (1u << 16)
> > +#define ADC_ECFLG    (1u << 15)
> > +#define ADC_PRSCEN   (1u << 14)
> > +#define ADC_PRSCLV(x)        (((x) & 0xFF) << 6)
> > +#define ADC_PRSCVLMASK       (0xFF << 6)
> > +#define ADC_STANDBY  (1u << 2)
> > +#define ADC_READ_START       (1u << 1)
> > +#define ADC_EN_START (1u << 0)
>
> You are a bit inconsistent with your prefixes, sometimes you use
> EXYNOS_ADC,
> sometimes just ADC, it would be better to use the same prefix all the
> time.
Will correct that.
>
> > +
> > +#define ADC_DATX_MASK        0xFFF
> > +
> > +struct exynos5_adc {
> > +     void __iomem            *regs;
> > +     struct clk              *clk;
> > +     unsigned int            irq;
> > +     struct regulator        *vdd;
> > +
> > +     struct completion       completion;
> > +
> > +     struct iio_map          *map;
> > +     u32                     value;
> > +     u32                     prescale;
> > +};
> > +
> > +static const struct of_device_id exynos5_adc_match[] = {
> > +     { .compatible = "samsung,exynos5250-adc" },
> > +     {},
> > +};
> > +MODULE_DEVICE_TABLE(of, exynos5_adc_match);
> > +
> > +/* default maps used by iio consumer (ex: ntc-thermistor driver) */
> > +static struct iio_map exynos5_adc_iio_maps[] = {
> > +     {
> > +             .consumer_dev_name = "0.ncp15wb473",
> > +             .consumer_channel = "adc_user3",
> > +             .adc_channel_label = "adc3",
> > +     },
> > +     {},
> > +};
>
> Hm... this should not be in the driver itself.
I've taken the example of "drivers/iio/adc/lp8788_adc.c"
I think this one is a tightly coupled driver.

Kindly, suggest me a better example.

>
> > +
> > +static int exynos5_read_raw(struct iio_dev *indio_dev,
> > +                             struct iio_chan_spec const *chan,
> > +                             int *val,
> > +                             int *val2,
> > +                             long mask)
> > +{
> > +     struct exynos5_adc *info = iio_priv(indio_dev);
> > +     u32 con;
> > +
> > +     if (mask == IIO_CHAN_INFO_RAW) {
> > +             mutex_lock(&indio_dev->mlock);
> > +
> > +             /* Select the channel to be used */
> > +             writel(chan->address, EXYNOS_ADC_MUX(info->regs));
> > +             /* Trigger conversion */
> > +             con = readl(EXYNOS_ADC_CON(info->regs));
> > +             writel(con | ADC_EN_START, EXYNOS_ADC_CON(info->regs));
> > +
> > +             wait_for_completion(&info->completion);
> > +             *val = info->value;
> > +
> > +             mutex_unlock(&indio_dev->mlock);
> > +
> > +             return IIO_VAL_INT;
> > +     }
> > +
> > +     return -EINVAL;
> > +}
> > +
> > +static irqreturn_t exynos5_adc_isr(int irq, void *dev_id)
> > +{
> > +     struct exynos5_adc *info = (struct exynos5_adc *)dev_id;
> > +
> > +     /* Read value and clear irq */
> > +     info->value = readl(EXYNOS_ADC_DATX(info->regs)) &
> > +                             ADC_DATX_MASK;
> > +     writel(0, EXYNOS_ADC_INTCLR(info->regs));
> > +
> > +     complete(&info->completion);
> > +
> > +     return IRQ_HANDLED;
> > +}
> > +
> > +static int exynos5_adc_reg_access(struct iio_dev *indio_dev,
> > +                           unsigned reg, unsigned writeval,
> > +                           unsigned *readval)
> > +{
> > +     struct exynos5_adc *info = iio_priv(indio_dev);
> > +     u32 ret;
> > +
> > +     mutex_lock(&indio_dev->mlock);
>
> Do we really need to take the lock here?
Took from the reference
>
> > +
> > +     if (readval != NULL) {
> > +             if (reg == 0x08)
> > +                     ret = readl(EXYNOS_ADC_DLY(info->regs));
> > +             else if (reg == 0x0C)
> > +                     ret = readl(EXYNOS_ADC_DATX(info->regs));
> > +             else if (reg == 0x1C)
> > +                     ret = readl(EXYNOS_ADC_MUX(info->regs));
> > +             else
> > +                     ret = readl(EXYNOS_ADC_CON(info->regs));
>
> How about
>                 ret = readl(info->regs + reg)
>
> instead of the whole if ... else if ... else if ...
Sure
>
> > +
> > +             readval = &ret;
>
> Uhm, I'm pretty sure that the line above does not work. At least it won't
> do
> what you want it to do.
Right, sorry
>
> > +     } else
> > +             ret = -EINVAL;
> > +
> > +     mutex_unlock(&indio_dev->mlock);
> > +
> > +     return ret;
> > +}
> > +
> > +static const struct iio_info exynos5_adc_iio_info = {
> > +     .read_raw = &exynos5_read_raw,
> > +     .debugfs_reg_access = &exynos5_adc_reg_access,
> > +     .driver_module = THIS_MODULE,
> > +};
> > +
> > +#define EXYNOS_ADC_CHANNEL(_index, _id) {            \
> > +     .type = IIO_VOLTAGE,                            \
> > +     .indexed = 1,                                   \
> > +     .channel = _index,                              \
> > +     .address = _index,                              \
> > +     .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT,    \
> > +     .datasheet_name = _id,                          \
> > +}
> > +
> > +static const struct iio_chan_spec exynos5_adc_iio_channels[] = {
> > +     EXYNOS_ADC_CHANNEL(0, "adc0"),
> > +     EXYNOS_ADC_CHANNEL(1, "adc1"),
> > +     EXYNOS_ADC_CHANNEL(2, "adc2"),
> > +     EXYNOS_ADC_CHANNEL(3, "adc3"),
> > +     EXYNOS_ADC_CHANNEL(4, "adc4"),
> > +     EXYNOS_ADC_CHANNEL(5, "adc5"),
> > +     EXYNOS_ADC_CHANNEL(6, "adc6"),
> > +     EXYNOS_ADC_CHANNEL(7, "adc7"),
The next version has 10 channels and future version are gonna support
more that that. May be my earlier doubt will fix this as well.
> > +};
> > +
> > +static int exynos5_adc_iio_map_register(struct iio_dev *indio_dev,
> > +                             struct exynos5_adc *adc)
> > +{
> > +     int ret;
> > +
> > +     adc->map = exynos5_adc_iio_maps;
> > +
> > +     ret = iio_map_array_register(indio_dev, adc->map);
> > +     if (ret) {
> > +             dev_err(&indio_dev->dev, "iio map err: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     return 0;
> > +}
>
> Just use iio_map_array_register instead of exynos5_adc_iio_map_register
>
> > +
> > +static inline void exynos5_adc_iio_map_unregister(struct iio_dev
> > *indio_dev,
> > +                             struct exynos5_adc *adc)
> > +{
> > +     iio_map_array_unregister(indio_dev, adc->map);
> > +}
>
> Just use iio_map_array_unregister directly instead of
> exynos5_adc_iio_map_unregister
>
> > +
> > +static int exynos5_adc_remove_devices(struct device *dev, void *c)
> > +{
> > +     struct platform_device *pdev = to_platform_device(dev);
> > +
> > +     platform_device_unregister(pdev);
> > +
> > +     return 0;
> > +}
>
> Again, a single line wrapper function...
This is a call back. So..
>
> > +
> > +static int exynos5_adc_probe(struct platform_device *pdev)
> > +{
> > +     struct exynos5_adc *info = NULL;
> > +     struct device_node *np = pdev->dev.of_node;
> > +     struct iio_dev *iodev = NULL;
>
> this is usually called indio_dev, would be good to be consistent across
> dirvers.
Sure.
>
> > +     struct resource *mem;
> > +     int ret = -ENODEV;
> > +     int irq;
> > +     u32 con;
> > +
> > +     iodev = iio_device_alloc(sizeof(struct exynos5_adc));
> > +     if (!iodev) {
> > +             dev_err(&pdev->dev, "failed allocating iio device\n");
> > +             return -ENOMEM;
> > +     }
> > +
> > +     info = iio_priv(iodev);
> > +
> > +     mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +     if (!mem) {
>
> devm_request_and_ioremap will check if mem is NULL, so you don't need to
> do
> this manually.
>
> > +             dev_err(&pdev->dev, "no mem resource?\n");
> > +             goto err_iio;
> > +     }
> > +
> > +     info->regs = devm_request_and_ioremap(&pdev->dev, mem);
> > +     if (!info->regs) {
> > +             dev_err(&pdev->dev, "cannot map EXYNOS5 ADC registers\n");
>
> devm_request_and_ioremap already prints an error message.
>
> > +             ret = -ENOMEM;
> > +             goto err_iio;
> > +     }
> > +
> > +     irq = platform_get_irq(pdev, 0);
> > +     if (irq < 0) {
> > +             dev_err(&pdev->dev, "no irq resource?\n");
> > +             ret = irq;
> > +             goto err_iio;
> > +     }
> > +
> > +     info->irq = irq;
> > +
> > +     ret = devm_request_irq(&pdev->dev, info->irq, exynos5_adc_isr,
> > +                                     0, dev_name(&pdev->dev), info);
>
> Using devm_request_irq is racy in this case, since the IRQ will be freed
> after the device has been freed, while it needs to be freed before the
> devie
> has been freed.
>
> > +     if (ret < 0) {
> > +             dev_err(&pdev->dev, "cannot request Samsung ADC IRQ %d\n",
> > +                                                     info->irq);
> > +             goto err_iio;
> > +     }
> > +
> > +     info->clk = devm_clk_get(&pdev->dev, "adc");
> > +     if (IS_ERR(info->clk)) {
> > +             dev_err(&pdev->dev, "failed getting clock\n");
>
> I think it is a good idea to include the error code in the error message.
>
> > +             ret = PTR_ERR(info->clk);
> > +             goto err_iio;
> > +     }
> > +
> > +     clk_enable(info->clk);
> > +
> > +     info->vdd = devm_regulator_get(&pdev->dev, "vdd");
> > +     if (IS_ERR(info->vdd)) {
> > +             dev_err(&pdev->dev, "operating without regulator \"vdd\"
> > .\n");
>
> Same here.
Sure
>
> > +             ret = PTR_ERR(info->vdd);
> > +             goto err_iio;
> > +     }
> > +
> > +     platform_set_drvdata(pdev, iodev);
> > +
> > +     init_completion(&info->completion);
> > +
> > +     iodev->name = dev_name(&pdev->dev);
> > +     iodev->dev.parent = &pdev->dev;
> > +     iodev->dev.of_node = pdev->dev.of_node;
> > +     iodev->info = &exynos5_adc_iio_info;
> > +     iodev->modes = INDIO_DIRECT_MODE;
> > +     iodev->channels = exynos5_adc_iio_channels;
> > +     iodev->num_channels = ARRAY_SIZE(exynos5_adc_iio_channels);
> > +
> > +     /* Enable prescaler and set platform default */
> > +     info->prescale = ADC_PRSCLV(49);
> > +     con = info->prescale | ADC_PRSCEN;
> > +
> > +     /* Enable 12-bit ADC resolution */
> > +     con |= ADC_RES;
> > +
> > +     writel(con, EXYNOS_ADC_CON(info->regs));
> > +
> > +     ret = exynos5_adc_iio_map_register(iodev, info);
> > +     if (ret)
> > +             goto err_iio;
> > +
> > +     ret = iio_device_register(iodev);
> > +     if (ret)
> > +             goto err_map;
> > +
> > +     ret = regulator_enable(info->vdd);
> > +     if (ret)
> > +             goto err_iio_dev;
> > +
> > +     ret = of_platform_populate(np, exynos5_adc_match, NULL,
> > &pdev->dev);
>
> Which kind of child nodes to you expect it to have? There is nothing about
> this in your dt bindings documentation.
I've tested with ntc thermistors (hwmon device) on a chromebook.
>
> > +     if (ret < 0) {
> > +             dev_err(&pdev->dev, "failed to add child nodes\n");
> > +             goto err_of_populate;
> > +     }
> > +
> > +     dev_info(&pdev->dev, "EXYNOS5 ADC driver loaded.\n");
>
> That's just noise, please remove it.
>
> > +
> > +     return 0;
> > +
> > +err_of_populate:
> > +     device_for_each_child(&pdev->dev, NULL,
> > exynos5_adc_remove_devices);
> > +err_iio_dev:
> > +     iio_device_unregister(iodev);
> > +err_map:
> > +     exynos5_adc_iio_map_unregister(iodev, info);
> > +err_iio:
> > +     iio_device_free(iodev);
> > +     return ret;
> > +}
> > +
> > +static int exynos5_adc_remove(struct platform_device *pdev)
> > +{
> > +     struct iio_dev *iodev = platform_get_drvdata(pdev);
> > +     struct exynos5_adc *info = iio_priv(iodev);
> > +
> > +     platform_set_drvdata(pdev, NULL);
>
> The line above should not be needed
>
> > +     iio_device_unregister(iodev);
> > +     exynos5_adc_iio_map_unregister(iodev, info);
> > +     iio_device_free(iodev);
> > +
> > +     return 0;
> > +}
> > +
> > +#ifdef CONFIG_PM
>
> CONFIG_PM_SLEEP
>
> > +static int exynos5_adc_suspend(struct device *dev)
> > +{
> > +     struct platform_device *pdev = container_of(dev,
> > +                     struct platform_device, dev);
>
> to_platform_device
>
> > +     struct exynos5_adc *info = platform_get_drvdata(pdev);
>
> Although using dev_get_data(dev) here would also be ok I guess.
>
> > +     u32 con;
> > +
> > +     con = readl(EXYNOS_ADC_CON(info->regs));
> > +     con |= ADC_STANDBY;
> > +     writel(con, EXYNOS_ADC_CON(info->regs));
> > +
> > +     clk_disable(info->clk);
>
> clk_unprepare_disable
Right, sure
>
> > +     regulator_disable(info->vdd);
> > +
> > +     return 0;
> > +}
> > +
> > +static int exynos5_adc_resume(struct device *dev)
> > +{
> > +     struct platform_device *pdev = container_of(dev,
> > +                     struct platform_device, dev);
>
> Same as above.
>
> > +     struct exynos5_adc *info = platform_get_drvdata(pdev);
> > +     unsigned int con;
> > +     int ret;
> > +
> > +     ret = regulator_enable(info->vdd);
> > +     if (ret)
> > +             return ret;
> > +
> > +     clk_enable(info->clk);
>
> clk_prepare_enable
>
> > +
> > +     /* TODO: Enable prescalar */
> > +     con = info->prescale | ADC_PRSCEN;
>
> I guess you need to enable the prescaler here ;) (or removed the TODO
> comment)
Sorry, missed to remove the comment
>
> > +     writel(con | ADC_RES, EXYNOS_ADC_CON(info->regs));
> > +
> > +     return 0;
> > +}
> > +
> > +#else
> > +#define s3c_adc_suspend NULL
> > +#define s3c_adc_resume NULL
> > +#endif
> > +
> > +static const struct dev_pm_ops adc_pm_ops = {
> > +     .suspend        = exynos5_adc_suspend,
> > +     .resume         = exynos5_adc_resume,
> > +};
>
> static SIMPLE_DEV_PM_OPS(exynos5_adc_pm_ops, exynos5_adc_suspend,
>         exynos5_adc_resume);
>
> > +
> > +static struct platform_driver exynos5_adc_driver = {
> > +     .probe          = exynos5_adc_probe,
> > +     .remove         = exynos5_adc_remove,
> > +     .driver         = {
> > +             .name   = "exynos5-adc",
> > +             .owner  = THIS_MODULE,
> > +             .of_match_table = of_match_ptr(exynos5_adc_match),
> > +             .pm     = &adc_pm_ops,
> > +     },
> > +};
> > +
> > +module_platform_driver(exynos5_adc_driver);
> > +
> > +MODULE_AUTHOR("Naveen Krishna Chatradhi <ch.naveen@...sung.com>");
> > +MODULE_DESCRIPTION("Samsung EXYNOS5 ADC driver");
> > +MODULE_LICENSE("GPL");
>

Lars, Thanks for your comments.
Will submit a V2 soon..

--
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(: Nav :)
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