rtc: ds1307: add frequency_test_enable attribute on m41txx

On m41txx you can enable open-drain OUT pin to check if offset is ok.
Enabling OUT pin with frequency_test_enable 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@micronovasrl.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 8268813..edccd0c 100644 (file)
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -1050,6 +1050,94 @@ static int m41txx_rtc_set_offset(struct device *dev, long offset)
                                  ctrl_reg);
 }
 
+static ssize_t frequency_test_enable_store(struct device *dev,
+                                          struct device_attribute *attr,
+                                          const char *buf, size_t count)
+{
+       struct ds1307 *ds1307 = dev_get_drvdata(dev);
+       bool freq_test_en;
+       int ret;
+
+       ret = kstrtobool(buf, &freq_test_en);
+       if (ret) {
+               dev_err(dev, "Failed to store RTC Frequency Test attribute\n");
+               return ret;
+       }
+
+       regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL, M41TXX_BIT_FT,
+                          freq_test_en ? M41TXX_BIT_FT : 0);
+
+       return count;
+}
+
+static ssize_t frequency_test_enable_show(struct device *dev,
+                                         struct device_attribute *attr,
+                                         char *buf)
+{
+       struct ds1307 *ds1307 = dev_get_drvdata(dev);
+       unsigned int ctrl_reg;
+
+       regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
+
+       return scnprintf(buf, PAGE_SIZE, (ctrl_reg & M41TXX_BIT_FT) ? "on\n" :
+                       "off\n");
+}
+
+static DEVICE_ATTR_RW(frequency_test_enable);
+
+static struct attribute *rtc_freq_test_attrs[] = {
+       &dev_attr_frequency_test_enable.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;
+
+       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);
+                       sysfs_remove_group(&(ds1307->dev)->kobj,
+                                          &rtc_freq_test_attr_group);
+                       return err;
+               }
+               break;
+       default:
+               break;
+       }
+
+       return 0;
+}
+
 /*----------------------------------------------------------------------*/
 
 static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
@@ -1792,6 +1880,10 @@ read_rtc:
        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",