linux-kernel - Re: [PATCH v3 4/4] rtc: ds1307: add freq_test sysfs attribute to check tick on m41txx

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Date:   Thu, 10 May 2018 23:46:49 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     a.zummo@...ertech.it, robh+dt@...nel.org, mark.rutland@....com,
        linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] rtc: ds1307: add freq_test sysfs attribute to
 check tick on m41txx

On 09/05/2018 21:33:55+0200, Giulio Benetti wrote:
> On m41txx you can enable open-drain OUT pin to check if offset is ok.
> Enabling OUT pin with freq_test attribute, OUT pin will tick 512 times
> faster than 1s tick base.
> 
> Enable or Disable FT bit on CONTROL register if freq_test is 1 or 0.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> ---
> V2 => V3: export freq_test on sysfs only if supported(m41txx series)
> 
>  drivers/rtc/rtc-ds1307.c | 107 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 107 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 33895668b363..79206bf21018 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -1042,6 +1042,109 @@ static int m41txx_rtc_set_offset(struct device *dev, long offset)
>  	return regmap_write(ds1307->regmap, M41TXX_REG_CONTROL,	ctrl_reg);
>  }
>  
> +static ssize_t freq_test_store(struct device *dev,
> +			       struct device_attribute *attr,
> +			       const char *buf, size_t count)
> +{
> +	struct ds1307 *ds1307 = dev_get_drvdata(dev);
> +	unsigned long freq_test = 0;
> +	unsigned int ctrl_reg;
> +	int retval;
> +
> +	retval = kstrtoul(buf, 10, &freq_test);
> +	if ((retval < 0) || (retval > 1)) {
> +		dev_err(dev, "Failed to store RTC Frequency Test attribute\n");
> +		return -EINVAL;
> +	}
> +
> +	regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
> +
> +	if (freq_test)
> +		ctrl_reg |= M41TXX_BIT_FT;
> +	else
> +		ctrl_reg &= ~M41TXX_BIT_FT;
> +
> +	retval = regmap_write(ds1307->regmap, M41TXX_REG_CONTROL, ctrl_reg);
> +

Pleas use regmap_update_bits

> +	return retval ? retval : count;
> +}
> +
> +static ssize_t freq_test_show(struct device *dev,
> +				    struct device_attribute *attr, char *buf)
> +{
> +	struct ds1307 *ds1307 = dev_get_drvdata(dev);
> +	int freq_test = 0;
> +	unsigned int ctrl_reg;
> +
> +	regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
> +
> +	if (ctrl_reg & M41TXX_BIT_FT)
> +		freq_test = true;
> +	else
> +		freq_test = false;
> +
> +	if ((freq_test < 0) || (freq_test > 1)) {

This will never happen

> +		dev_err(dev, "Failed to read RTC Frequency Test\n");
> +		sprintf(buf, "0\n");
> +		return freq_test;
> +	}
> +
> +	return sprintf(buf, "%d\n", freq_test);
> +}
> +
> +static DEVICE_ATTR_RW(freq_test);

I'd prefer the file to be named frequency_test_enable

> +
> +static struct attribute *rtc_freq_test_attrs[] = {
> +	&dev_attr_freq_test.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group rtc_freq_test_attr_group = {
> +	.attrs		= rtc_freq_test_attrs,
> +};
> +
> +static void rtc_calib_remove_sysfs_group(void *_dev)
> +{
> +	struct device *dev = _dev;
> +
> +	sysfs_remove_group(&dev->kobj, &rtc_freq_test_attr_group);
> +}
> +
> +static int ds1307_add_frequency_test(struct ds1307 *ds1307)
> +{
> +	int err = 0;
> +
> +	switch (ds1307->type) {
> +	case m41t0:
> +	case m41t00:
> +	case m41t11:
> +		/* Export sysfs entries */
> +		err = sysfs_create_group(&(ds1307->dev)->kobj,
> +					 &rtc_freq_test_attr_group);
> +		if (err) {
> +			dev_err(ds1307->dev,
> +				"Failed to create sysfs group: %d\n",
> +				err);
> +			return err;
> +		}
> +
> +		err = devm_add_action_or_reset(ds1307->dev,
> +					       rtc_calib_remove_sysfs_group,
> +					       ds1307->dev);
> +		if (err) {
> +			dev_err(ds1307->dev,
> +				"Failed to add sysfs cleanup action: %d\n",
> +				err);

You need to sysfs_remove_group here

> +			return err;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return err;
> +}
> +
>  /*----------------------------------------------------------------------*/
>  
>  static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
> @@ -1783,6 +1886,10 @@ static int ds1307_probe(struct i2c_client *client,
>  	if (err)
>  		return err;
>  
> +	err = ds1307_add_frequency_test(ds1307);
> +	if (err)
> +		return err;
> +
>  	if (chip->nvram_size) {
>  		struct nvmem_config nvmem_cfg = {
>  			.name = "ds1307_nvram",
> -- 
> 2.17.0
> 

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com