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rtc: abx80x: handle autocalibration
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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 <[email protected]>
Signed-off-by: Alexandre Belloni <[email protected]>
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@alexandrebelloni
Mylène Josserand authored and alexandrebelloni committed Mar 25, 2016
1 parent 85062c9 commit 59a8383
Showing 1 changed file with 219 additions and 0 deletions.
219 changes: 219 additions & 0 deletions drivers/rtc/rtc-abx80x.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -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;
}

Expand Down

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