[PATCH] rtc: isl12026: Implement callbacks for alarm feature

[PATCH] rtc: isl12026: Implement callbacks for alarm feature

[Akhilesh Patil]

Add alarm support for isl12026 RTC. Implement alarm function rtc
class callbacks - set_alarm, read_alarm and alarm_irq_enable.
isl12026 rtc has 2 alarms, this patch adds support to configure alarm0.
Note: isl12026 rtc chip share same pin(4) for alarm interrupt and square
wave frequency generator, hence forcefully disable SQW functionality
while writing to device registers in alarm functions.

Tested on TI am62x sk board on i2c-2 port using selftests/rtc/rtctest

Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
---
Datasheet of RTC chip.
https://www.renesas.com/en/document/dst/isl12026-isl12026a-datasheet?srsltid=AfmBOopgN4vtn8XoN-8sOCfTW6yiLH-T7eeH_IWakqZ2VmENmWFqqh7w

 drivers/rtc/rtc-isl12026.c | 127 +++++++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)

diff --git a/drivers/rtc/rtc-isl12026.c b/drivers/rtc/rtc-isl12026.c
index 2aabb9151d4c..7fa9ec7e4929 100644
--- a/drivers/rtc/rtc-isl12026.c
+++ b/drivers/rtc/rtc-isl12026.c
@@ -34,6 +34,11 @@
 #define ISL12026_PAGESIZE 16
 #define ISL12026_NVMEM_WRITE_TIME 20
 
+#define ISL12026_AL0_REG_SC	0x0
+#define ISL12026_REG_INT	0x11
+#define ISL12026_AL0E		BIT(5)
+#define ISL12026_SR_AL0         BIT(5)
+
 struct isl12026 {
 	struct rtc_device *rtc;
 	struct i2c_client *nvm_client;
@@ -269,9 +274,131 @@ static int isl12026_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	return ret;
 }
 
+static int isl12026_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int ret;
+	u8 buf_alrm_vals[7];
+	struct i2c_msg msg;
+	int ir;
+
+	msg.addr = client->addr;
+	msg.flags = 0x0; /* Write operation */
+	msg.buf = buf_alrm_vals;
+	msg.len = sizeof(buf_alrm_vals);
+
+	if (!alrm->enabled) {
+		/* Disable alarm and return */
+		ir = isl12026_read_reg(client, ISL12026_REG_INT);
+		if (ir < 0)
+			return ir;
+		ir &= ~ISL12026_AL0E;
+		ret = isl12026_write_reg(client, ISL12026_REG_INT, ir);
+
+		return ret;
+	}
+
+	/* Prepare 5 bytes alarm data SC, MN, HR, DT, MO */
+	buf_alrm_vals[0] = 0x0;
+	buf_alrm_vals[1] = ISL12026_AL0_REG_SC;
+	buf_alrm_vals[2] = (bin2bcd(alrm->time.tm_sec) & 0x7f) | 0x80;
+	buf_alrm_vals[3] = (bin2bcd(alrm->time.tm_min) & 0x7f) | 0x80;
+	buf_alrm_vals[4] = (bin2bcd(alrm->time.tm_hour) & 0x3f) | 0x80;
+	buf_alrm_vals[5] = (bin2bcd(alrm->time.tm_mday) & 0x3f) | 0x80;
+	buf_alrm_vals[6] = (bin2bcd(alrm->time.tm_mon + 1) & 0x1f) | 0x80;
+
+	/* Non-volatile Page write to AL0 registers and enable INT */
+	ret = isl12026_arm_write(client);
+	if (ret < 0)
+		return ret;
+	ret = i2c_transfer(client->adapter, &msg, 1);
+	msleep(ISL12026_NVMEM_WRITE_TIME);
+	if (ret != 1) {
+		dev_err(&client->dev, "Error writing to alarm registers\n");
+		return ret < 0 ? ret : -EIO;
+	}
+
+	/* Enable AL0 interrupt */
+	ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
+
+	return ret;
+}
+
+static int isl12026_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int ret;
+	int sr, ir;
+	u8 buf_alrm_vals[5];
+	u8 addr[2] = {0x0, ISL12026_AL0_REG_SC};
+	struct i2c_msg msgs[2] = { };
+
+	msgs[0].addr = client->addr;
+	msgs[0].flags = 0x0; /* Write register address */
+	msgs[0].buf = addr;
+	msgs[0].len = sizeof(addr);
+
+	msgs[1].addr = client->addr;
+	msgs[1].flags = I2C_M_RD; /* Alarm read operation */
+	msgs[1].buf = buf_alrm_vals;
+	msgs[1].len = sizeof(buf_alrm_vals);
+
+	/* Read alarm enable status */
+	ir = isl12026_read_reg(client, ISL12026_REG_INT);
+	if (ir < 0)
+		return ir;
+	alrm->enabled =  !!(ir & ISL12026_AL0E);
+
+	/* Read alarm pending status */
+	sr = isl12026_read_reg(client, ISL12026_REG_SR);
+	if (sr < 0)
+		return sr;
+	alrm->pending =  !!(sr & ISL12026_SR_AL0) && alrm->enabled;
+
+	/* Page read for alarm registers */
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "Error reading alarm registers\n");
+		return ret < 0 ? ret : -EIO;
+	}
+
+	/* Populate values read */
+	alrm->time.tm_sec =  bcd2bin(buf_alrm_vals[0] & 0x7f);
+	alrm->time.tm_min =  bcd2bin(buf_alrm_vals[1] & 0x7f);
+	alrm->time.tm_hour = bcd2bin(buf_alrm_vals[2] & 0x3f);
+	alrm->time.tm_mday = bcd2bin(buf_alrm_vals[3] & 0x3f);
+	alrm->time.tm_mon =  bcd2bin(buf_alrm_vals[4] & 0x1f) - 1;
+
+	return 0;
+}
+
+static int isl12026_rtc_alarm_irq_en(struct device *dev, unsigned int enabled)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int ret;
+	int ir;
+
+	if (enabled) {
+		ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
+		return ret;
+	}
+
+	/* Disable alarm */
+	ir = isl12026_read_reg(client, ISL12026_REG_INT);
+	if (ir < 0)
+		return ir;
+	ir &= ~ISL12026_AL0E;
+	ret = isl12026_write_reg(client, ISL12026_REG_INT, ir);
+
+	return ret;
+}
+
 static const struct rtc_class_ops isl12026_rtc_ops = {
 	.read_time	= isl12026_rtc_read_time,
 	.set_time	= isl12026_rtc_set_time,
+	.set_alarm	= isl12026_rtc_set_alarm,
+	.read_alarm	= isl12026_rtc_read_alarm,
+	.alarm_irq_enable = isl12026_rtc_alarm_irq_en,
 };
 
 static int isl12026_nvm_read(void *p, unsigned int offset,
-- 
2.34.1

Re: [PATCH] rtc: isl12026: Implement callbacks for alarm feature

[Alexandre Belloni]

On 15/11/2025 16:35:06+0530, Akhilesh Patil wrote:
> Add alarm support for isl12026 RTC. Implement alarm function rtc
> class callbacks - set_alarm, read_alarm and alarm_irq_enable.
> isl12026 rtc has 2 alarms, this patch adds support to configure alarm0.
> Note: isl12026 rtc chip share same pin(4) for alarm interrupt and square
> wave frequency generator, hence forcefully disable SQW functionality
> while writing to device registers in alarm functions.
> 
> Tested on TI am62x sk board on i2c-2 port using selftests/rtc/rtctest
> 
> Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
> ---
> Datasheet of RTC chip.
> https://www.renesas.com/en/document/dst/isl12026-isl12026a-datasheet?srsltid=AfmBOopgN4vtn8XoN-8sOCfTW6yiLH-T7eeH_IWakqZ2VmENmWFqqh7w
> 
>  drivers/rtc/rtc-isl12026.c | 127 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 127 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-isl12026.c b/drivers/rtc/rtc-isl12026.c
> index 2aabb9151d4c..7fa9ec7e4929 100644
> --- a/drivers/rtc/rtc-isl12026.c
> +++ b/drivers/rtc/rtc-isl12026.c
> @@ -34,6 +34,11 @@
>  #define ISL12026_PAGESIZE 16
>  #define ISL12026_NVMEM_WRITE_TIME 20
>  
> +#define ISL12026_AL0_REG_SC	0x0
> +#define ISL12026_REG_INT	0x11
> +#define ISL12026_AL0E		BIT(5)
> +#define ISL12026_SR_AL0         BIT(5)
> +
>  struct isl12026 {
>  	struct rtc_device *rtc;
>  	struct i2c_client *nvm_client;
> @@ -269,9 +274,131 @@ static int isl12026_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  	return ret;
>  }
>  
> +static int isl12026_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	int ret;
> +	u8 buf_alrm_vals[7];
> +	struct i2c_msg msg;
> +	int ir;
> +
> +	msg.addr = client->addr;
> +	msg.flags = 0x0; /* Write operation */
> +	msg.buf = buf_alrm_vals;
> +	msg.len = sizeof(buf_alrm_vals);
> +
> +	if (!alrm->enabled) {
> +		/* Disable alarm and return */

You still need to set the alarm time and date properly, the application
is allowed to first set the alarm and then enable it.

> +		ir = isl12026_read_reg(client, ISL12026_REG_INT);
> +		if (ir < 0)
> +			return ir;
> +		ir &= ~ISL12026_AL0E;
> +		ret = isl12026_write_reg(client, ISL12026_REG_INT, ir);
> +
> +		return ret;
> +	}
> +
> +	/* Prepare 5 bytes alarm data SC, MN, HR, DT, MO */
> +	buf_alrm_vals[0] = 0x0;
> +	buf_alrm_vals[1] = ISL12026_AL0_REG_SC;
> +	buf_alrm_vals[2] = (bin2bcd(alrm->time.tm_sec) & 0x7f) | 0x80;
> +	buf_alrm_vals[3] = (bin2bcd(alrm->time.tm_min) & 0x7f) | 0x80;
> +	buf_alrm_vals[4] = (bin2bcd(alrm->time.tm_hour) & 0x3f) | 0x80;
> +	buf_alrm_vals[5] = (bin2bcd(alrm->time.tm_mday) & 0x3f) | 0x80;
> +	buf_alrm_vals[6] = (bin2bcd(alrm->time.tm_mon + 1) & 0x1f) | 0x80;
> +
> +	/* Non-volatile Page write to AL0 registers and enable INT */
> +	ret = isl12026_arm_write(client);
> +	if (ret < 0)
> +		return ret;
> +	ret = i2c_transfer(client->adapter, &msg, 1);
> +	msleep(ISL12026_NVMEM_WRITE_TIME);
> +	if (ret != 1) {
> +		dev_err(&client->dev, "Error writing to alarm registers\n");

No need for an error message.

> +		return ret < 0 ? ret : -EIO;
> +	}
> +
> +	/* Enable AL0 interrupt */
> +	ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
> +
> +	return ret;
> +}
> +
> +static int isl12026_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	int ret;
> +	int sr, ir;
> +	u8 buf_alrm_vals[5];
> +	u8 addr[2] = {0x0, ISL12026_AL0_REG_SC};
> +	struct i2c_msg msgs[2] = { };
> +
> +	msgs[0].addr = client->addr;
> +	msgs[0].flags = 0x0; /* Write register address */
> +	msgs[0].buf = addr;
> +	msgs[0].len = sizeof(addr);
> +
> +	msgs[1].addr = client->addr;
> +	msgs[1].flags = I2C_M_RD; /* Alarm read operation */
> +	msgs[1].buf = buf_alrm_vals;
> +	msgs[1].len = sizeof(buf_alrm_vals);
> +
> +	/* Read alarm enable status */
> +	ir = isl12026_read_reg(client, ISL12026_REG_INT);
> +	if (ir < 0)
> +		return ir;
> +	alrm->enabled =  !!(ir & ISL12026_AL0E);
> +
> +	/* Read alarm pending status */
> +	sr = isl12026_read_reg(client, ISL12026_REG_SR);
> +	if (sr < 0)
> +		return sr;
> +	alrm->pending =  !!(sr & ISL12026_SR_AL0) && alrm->enabled;
> +
> +	/* Page read for alarm registers */
> +	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> +	if (ret != ARRAY_SIZE(msgs)) {
> +		dev_err(&client->dev, "Error reading alarm registers\n");

Ditto

> +		return ret < 0 ? ret : -EIO;
> +	}
> +
> +	/* Populate values read */
> +	alrm->time.tm_sec =  bcd2bin(buf_alrm_vals[0] & 0x7f);
> +	alrm->time.tm_min =  bcd2bin(buf_alrm_vals[1] & 0x7f);
> +	alrm->time.tm_hour = bcd2bin(buf_alrm_vals[2] & 0x3f);
> +	alrm->time.tm_mday = bcd2bin(buf_alrm_vals[3] & 0x3f);
> +	alrm->time.tm_mon =  bcd2bin(buf_alrm_vals[4] & 0x1f) - 1;
> +
> +	return 0;
> +}
> +
> +static int isl12026_rtc_alarm_irq_en(struct device *dev, unsigned int enabled)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	int ret;
> +	int ir;
> +
> +	if (enabled) {
> +		ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
> +		return ret;
> +	}
> +
> +	/* Disable alarm */
> +	ir = isl12026_read_reg(client, ISL12026_REG_INT);
> +	if (ir < 0)
> +		return ir;
> +	ir &= ~ISL12026_AL0E;
> +	ret = isl12026_write_reg(client, ISL12026_REG_INT, ir);
> +
> +	return ret;
> +}
> +
>  static const struct rtc_class_ops isl12026_rtc_ops = {
>  	.read_time	= isl12026_rtc_read_time,
>  	.set_time	= isl12026_rtc_set_time,
> +	.set_alarm	= isl12026_rtc_set_alarm,
> +	.read_alarm	= isl12026_rtc_read_alarm,
> +	.alarm_irq_enable = isl12026_rtc_alarm_irq_en,
>  };
>  

This is missing an interrupt handler and proper handling in probe for
the wakeup-source property as this seems to be how you use it.


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] rtc: isl12026: Implement callbacks for alarm feature

[Akhilesh Patil]

On Sat, Nov 15, 2025 at 12:24:21PM +0100, Alexandre Belloni wrote:
> On 15/11/2025 16:35:06+0530, Akhilesh Patil wrote:
> > Add alarm support for isl12026 RTC. Implement alarm function rtc
> > class callbacks - set_alarm, read_alarm and alarm_irq_enable.
> > isl12026 rtc has 2 alarms, this patch adds support to configure alarm0.
> > Note: isl12026 rtc chip share same pin(4) for alarm interrupt and square
> > wave frequency generator, hence forcefully disable SQW functionality
> > while writing to device registers in alarm functions.
> > 
> > Tested on TI am62x sk board on i2c-2 port using selftests/rtc/rtctest
> > 
> > Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
> > ---
> > Datasheet of RTC chip.
> > https://www.renesas.com/en/document/dst/isl12026-isl12026a-datasheet?srsltid=AfmBOopgN4vtn8XoN-8sOCfTW6yiLH-T7eeH_IWakqZ2VmENmWFqqh7w
> > 
> >  drivers/rtc/rtc-isl12026.c | 127 +++++++++++++++++++++++++++++++++++++
> >  1 file changed, 127 insertions(+)
> > 
> > diff --git a/drivers/rtc/rtc-isl12026.c b/drivers/rtc/rtc-isl12026.c
> > index 2aabb9151d4c..7fa9ec7e4929 100644
> > --- a/drivers/rtc/rtc-isl12026.c
> > +++ b/drivers/rtc/rtc-isl12026.c
> > @@ -34,6 +34,11 @@
> >  #define ISL12026_PAGESIZE 16
> >  #define ISL12026_NVMEM_WRITE_TIME 20

Hi Alexandre, Thanks for the review.
Please find my comments below.

[...]

> >  
> > +static int isl12026_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	int ret;
> > +	u8 buf_alrm_vals[7];
> > +	struct i2c_msg msg;
> > +	int ir;
> > +
> > +	msg.addr = client->addr;
> > +	msg.flags = 0x0; /* Write operation */
> > +	msg.buf = buf_alrm_vals;
> > +	msg.len = sizeof(buf_alrm_vals);
> > +
> > +	if (!alrm->enabled) {
> > +		/* Disable alarm and return */
> 
> You still need to set the alarm time and date properly, the application
> is allowed to first set the alarm and then enable it.

Sure. Understood.
Will fix this in v2.

> 
> > +		ir = isl12026_read_reg(client, ISL12026_REG_INT);
> > +		if (ir < 0)
> > +			return ir;
> > +		ir &= ~ISL12026_AL0E;

[...]

> > +
> > +	/* Non-volatile Page write to AL0 registers and enable INT */
> > +	ret = isl12026_arm_write(client);
> > +	if (ret < 0)
> > +		return ret;
> > +	ret = i2c_transfer(client->adapter, &msg, 1);
> > +	msleep(ISL12026_NVMEM_WRITE_TIME);
> > +	if (ret != 1) {
> > +		dev_err(&client->dev, "Error writing to alarm registers\n");
> 
> No need for an error message.

ACK.
Will remove error message and just return error.

> 
> > +		return ret < 0 ? ret : -EIO;
> > +	}
> > +
> > +	/* Enable AL0 interrupt */
> > +	ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
> > +
> > +	return ret;
> > +}
> > +
> > +static int isl12026_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	int ret;
> > +	int sr, ir;
> > +	u8 buf_alrm_vals[5];
> > +	u8 addr[2] = {0x0, ISL12026_AL0_REG_SC};
> > +	struct i2c_msg msgs[2] = { };
> > +

[...]

> > +	alrm->pending =  !!(sr & ISL12026_SR_AL0) && alrm->enabled;
> > +
> > +	/* Page read for alarm registers */
> > +	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> > +	if (ret != ARRAY_SIZE(msgs)) {
> > +		dev_err(&client->dev, "Error reading alarm registers\n");
> 
> Ditto

ACK. Will remove err message.

> 
> > +		return ret < 0 ? ret : -EIO;
> > +	}
> > +
> > +	/* Populate values read */
> > +	alrm->time.tm_sec =  bcd2bin(buf_alrm_vals[0] & 0x7f);
> > +	alrm->time.tm_min =  bcd2bin(buf_alrm_vals[1] & 0x7f);
> > +	alrm->time.tm_hour = bcd2bin(buf_alrm_vals[2] & 0x3f);
> > +	alrm->time.tm_mday = bcd2bin(buf_alrm_vals[3] & 0x3f);
> > +	alrm->time.tm_mon =  bcd2bin(buf_alrm_vals[4] & 0x1f) - 1;
> > +
> > +	return 0;
> > +}
> > +
> > +static int isl12026_rtc_alarm_irq_en(struct device *dev, unsigned int enabled)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	int ret;
> > +	int ir;
> > +
> > +	if (enabled) {
> > +		ret = isl12026_write_reg(client, ISL12026_REG_INT, ISL12026_AL0E);
> > +		return ret;
> > +	}
> > +
> > +	/* Disable alarm */
> > +	ir = isl12026_read_reg(client, ISL12026_REG_INT);
> > +	if (ir < 0)
> > +		return ir;
> > +	ir &= ~ISL12026_AL0E;
> > +	ret = isl12026_write_reg(client, ISL12026_REG_INT, ir);
> > +
> > +	return ret;
> > +}
> > +
> >  static const struct rtc_class_ops isl12026_rtc_ops = {
> >  	.read_time	= isl12026_rtc_read_time,
> >  	.set_time	= isl12026_rtc_set_time,
> > +	.set_alarm	= isl12026_rtc_set_alarm,
> > +	.read_alarm	= isl12026_rtc_read_alarm,
> > +	.alarm_irq_enable = isl12026_rtc_alarm_irq_en,
> >  };
> >  
> 
> This is missing an interrupt handler and proper handling in probe for
> the wakeup-source property as this seems to be how you use it.

Agree. However, I thought of first implementing alarm callbacks only and
test them independedntly using ioctls for alarm settings in this patch.
I will add interrupt handler and wakeup-source in v2 to complete this
functionality.

Regards,
Akhilesh

> 
> 
> -- 
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

Re: [PATCH] rtc: isl12026: Implement callbacks for alarm feature

[Alexandre Belloni]

On 16/11/2025 10:47:15+0530, Akhilesh Patil wrote:
> > >  static const struct rtc_class_ops isl12026_rtc_ops = {
> > >  	.read_time	= isl12026_rtc_read_time,
> > >  	.set_time	= isl12026_rtc_set_time,
> > > +	.set_alarm	= isl12026_rtc_set_alarm,
> > > +	.read_alarm	= isl12026_rtc_read_alarm,
> > > +	.alarm_irq_enable = isl12026_rtc_alarm_irq_en,
> > >  };
> > >  
> > 
> > This is missing an interrupt handler and proper handling in probe for
> > the wakeup-source property as this seems to be how you use it.
> 
> Agree. However, I thought of first implementing alarm callbacks only and
> test them independedntly using ioctls for alarm settings in this patch.
> I will add interrupt handler and wakeup-source in v2 to complete this
> functionality.

Sure, the issue is that without interrupt handling and wakeup-source,
the driver will behave in a way that will break DT backward
compatibility later on.

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com