rtc: abx80x: handle autocalibration

The autocalibration is separated in two bits to set in Oscillator
Control register (0x1c) :
 - OSEL bit to select the oscillator type (XT or RC).
 - ACAL bit to select the autocalibration type.

These functionnalities are exported in sysfs entries : "oscillator"
and "autocalibration". Respectively, the values are "xtal" for XT
oscillator and "rc" for RC oscillator and 0 to disable the
autocalibration cycle, 512 for a 512 seconds autocalibration cycle
and 1024 for a cycle of 1024 seconds.

Examples :
Set to XT Oscillator
echo xtal > /sys/class/rtc/rtc0/device/oscillator
Activate an autocalibration every 512 seconds
echo 512 > /sys/class/rtc/rtc0/device/autocalibration

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

1 files changed, 219 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
index d41bbcd653f6..0e4c9a0989d1 100644
--- a/drivers/rtc/rtc-abx80x.c
+++ b/drivers/rtc/rtc-abx80x.c
@@ -49,7 +49,19 @@
 
 #define ABX8XX_REG_CD_TIMER_CTL 0x18
 
+#define ABX8XX_REG_OSC          0x1c
+#define ABX8XX_OSC_FOS          BIT(3)
+#define ABX8XX_OSC_BOS          BIT(4)
+#define ABX8XX_OSC_ACAL_512     BIT(5)
+#define ABX8XX_OSC_ACAL_1024    BIT(6)
+
+#define ABX8XX_OSC_OSEL         BIT(7)
+
+#define ABX8XX_REG_OSS          0x1d
+#define ABX8XX_OSS_OMODE        BIT(4)
+
 #define ABX8XX_REG_CFG_KEY      0x1f
+#define ABX8XX_CFG_KEY_OSC      0xa1
 #define ABX8XX_CFG_KEY_MISC     0x9d
 
 #define ABX8XX_REG_ID0          0x28
@@ -81,6 +93,20 @@ static struct abx80x_cap abx80x_caps[] = {
         [ABX80X] = {.pn = 0}
 };
 
+static int abx80x_is_rc_mode(struct i2c_client *client)
+{
+        int flags = 0;
+
+        flags =  i2c_smbus_read_byte_data(client, ABX8XX_REG_OSS);
+        if (flags < 0) {
+                dev_err(&client->dev,
+                        "Failed to read autocalibration attribute\n");
+                return flags;
+        }
+
+        return (flags & ABX8XX_OSS_OMODE) ? 1 : 0;
+}
+
 static int abx80x_enable_trickle_charger(struct i2c_client *client,
                                          u8 trickle_cfg)
 {
@@ -248,6 +274,174 @@ static int abx80x_set_alarm(struct device *dev, struct rtc_wkalrm *t)
         return 0;
 }
 
+static int abx80x_rtc_set_autocalibration(struct device *dev,
+                                          int autocalibration)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        int retval, flags = 0;
+
+        if ((autocalibration != 0) && (autocalibration != 1024) &&
+            (autocalibration != 512)) {
+                dev_err(dev, "autocalibration value outside permitted range\n");
+                return -EINVAL;
+        }
+
+        flags = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
+        if (flags < 0)
+                return flags;
+
+        if (autocalibration == 0) {
+                flags &= ~(ABX8XX_OSC_ACAL_512 | ABX8XX_OSC_ACAL_1024);
+        } else if (autocalibration == 1024) {
+                /* 1024 autocalibration is 0x10 */
+                flags |= ABX8XX_OSC_ACAL_1024;
+                flags &= ~(ABX8XX_OSC_ACAL_512);
+        } else {
+                /* 512 autocalibration is 0x11 */
+                flags |= (ABX8XX_OSC_ACAL_1024 | ABX8XX_OSC_ACAL_512);
+        }
+
+        /* Unlock write access to Oscillator Control Register */
+        retval = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+                                           ABX8XX_CFG_KEY_OSC);
+        if (retval < 0) {
+                dev_err(dev, "Failed to write CONFIG_KEY register\n");
+                return retval;
+        }
+
+        retval = i2c_smbus_write_byte_data(client, ABX8XX_REG_OSC, flags);
+
+        return retval;
+}
+
+static int abx80x_rtc_get_autocalibration(struct device *dev)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        int flags = 0, autocalibration;
+
+        flags =  i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
+        if (flags < 0)
+                return flags;
+
+        if (flags & ABX8XX_OSC_ACAL_512)
+                autocalibration = 512;
+        else if (flags & ABX8XX_OSC_ACAL_1024)
+                autocalibration = 1024;
+        else
+                autocalibration = 0;
+
+        return autocalibration;
+}
+
+static ssize_t autocalibration_store(struct device *dev,
+                                     struct device_attribute *attr,
+                                     const char *buf, size_t count)
+{
+        int retval;
+        unsigned long autocalibration = 0;
+
+        retval = kstrtoul(buf, 10, &autocalibration);
+        if (retval < 0) {
+                dev_err(dev, "Failed to store RTC autocalibration attribute\n");
+                return -EINVAL;
+        }
+
+        retval = abx80x_rtc_set_autocalibration(dev, autocalibration);
+
+        return retval ? retval : count;
+}
+
+static ssize_t autocalibration_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+        int autocalibration = 0;
+
+        autocalibration = abx80x_rtc_get_autocalibration(dev);
+        if (autocalibration < 0) {
+                dev_err(dev, "Failed to read RTC autocalibration\n");
+                sprintf(buf, "0\n");
+                return autocalibration;
+        }
+
+        return sprintf(buf, "%d\n", autocalibration);
+}
+
+static DEVICE_ATTR_RW(autocalibration);
+
+static ssize_t oscillator_store(struct device *dev,
+                                struct device_attribute *attr,
+                                const char *buf, size_t count)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        int retval, flags, rc_mode = 0;
+
+        if (strncmp(buf, "rc", 2) == 0) {
+                rc_mode = 1;
+        } else if (strncmp(buf, "xtal", 4) == 0) {
+                rc_mode = 0;
+        } else {
+                dev_err(dev, "Oscillator selection value outside permitted ones\n");
+                return -EINVAL;
+        }
+
+        flags =  i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
+        if (flags < 0)
+                return flags;
+
+        if (rc_mode == 0)
+                flags &= ~(ABX8XX_OSC_OSEL);
+        else
+                flags |= (ABX8XX_OSC_OSEL);
+
+        /* Unlock write access on Oscillator Control register */
+        retval = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+                                           ABX8XX_CFG_KEY_OSC);
+        if (retval < 0) {
+                dev_err(dev, "Failed to write CONFIG_KEY register\n");
+                return retval;
+        }
+
+        retval = i2c_smbus_write_byte_data(client, ABX8XX_REG_OSC, flags);
+        if (retval < 0) {
+                dev_err(dev, "Failed to write Oscillator Control register\n");
+                return retval;
+        }
+
+        return retval ? retval : count;
+}
+
+static ssize_t oscillator_show(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+        int rc_mode = 0;
+        struct i2c_client *client = to_i2c_client(dev);
+
+        rc_mode = abx80x_is_rc_mode(client);
+
+        if (rc_mode < 0) {
+                dev_err(dev, "Failed to read RTC oscillator selection\n");
+                sprintf(buf, "\n");
+                return rc_mode;
+        }
+
+        if (rc_mode)
+                return sprintf(buf, "rc\n");
+        else
+                return sprintf(buf, "xtal\n");
+}
+
+static DEVICE_ATTR_RW(oscillator);
+
+static struct attribute *rtc_calib_attrs[] = {
+        &dev_attr_autocalibration.attr,
+        &dev_attr_oscillator.attr,
+        NULL,
+};
+
+static const struct attribute_group rtc_calib_attr_group = {
+        .attrs          = rtc_calib_attrs,
+};
+
 static int abx80x_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
         struct i2c_client *client = to_i2c_client(dev);
@@ -303,6 +497,13 @@ static int abx80x_dt_trickle_cfg(struct device_node *np)
         return (trickle_cfg | i);
 }
 
+static void rtc_calib_remove_sysfs_group(void *_dev)
+{
+        struct device *dev = _dev;
+
+        sysfs_remove_group(&dev->kobj, &rtc_calib_attr_group);
+}
+
 static int abx80x_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
 {
@@ -405,6 +606,24 @@ static int abx80x_probe(struct i2c_client *client,
                 }
         }
 
+        /* Export sysfs entries */
+        err = sysfs_create_group(&(&client->dev)->kobj, &rtc_calib_attr_group);
+        if (err) {
+                dev_err(&client->dev, "Failed to create sysfs group: %d\n",
+                        err);
+                return err;
+        }
+
+        err = devm_add_action(&client->dev, rtc_calib_remove_sysfs_group,
+                              &client->dev);
+        if (err) {
+                rtc_calib_remove_sysfs_group(&client->dev);
+                dev_err(&client->dev,
+                        "Failed to add sysfs cleanup action: %d\n",
+                        err);
+                return err;
+        }
+
         return 0;
 }