rtc: ds1307: Add support for Epson RX8901CE

[PATCH 4/4] rtc: ds1307: Add support for reading RX8901CE battery VL status

Posted by Fredrik M Olsson 1 month, 3 weeks ago

Adds support for:
- Reading the battery voltage low status using the RTC_VL_READ ioctl,
  which also reports invalid time information if the VLF flag is set.

Signed-off-by: Fredrik M Olsson <fredrik.m.olsson@axis.com>
---
 drivers/rtc/rtc-ds1307.c | 46 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 43 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 99d95e520108..ca062ed0c867 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -133,8 +133,11 @@ enum ds_type {
 #define RX8901_REG_INTF			0x0e
 #define RX8901_REG_INTF_VLF		BIT(1)
 #define RX8901_REG_PWSW_CFG		0x37
+#define RX8901_REG_PWSW_CFG_VBATLDETEN	BIT(4)
 #define RX8901_REG_PWSW_CFG_INIEN	BIT(6)
 #define RX8901_REG_PWSW_CFG_CHGEN	BIT(7)
+#define RX8901_REG_BUF_INTF		0x46
+#define RX8901_REG_BUF_INTF_VBATLF	BIT(3)
 
 #define MCP794XX_REG_CONTROL		0x07
 #	define MCP794XX_BIT_ALM0_EN	0x10
@@ -458,6 +461,39 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
 	return 0;
 }
 
+#ifdef CONFIG_RTC_INTF_DEV
+static int rx8901_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct ds1307 *ds1307 = dev_get_drvdata(dev);
+	unsigned int regflag, tmp = 0;
+	int ret = 0;
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		ret = regmap_read(ds1307->regmap, RX8901_REG_INTF, &regflag);
+		if (ret)
+			return ret;
+
+		if (regflag & RX8901_REG_INTF_VLF)
+			tmp |= RTC_VL_DATA_INVALID;
+
+		ret = regmap_read(ds1307->regmap, RX8901_REG_BUF_INTF, &regflag);
+		if (ret)
+			return ret;
+
+		if (regflag & RX8901_REG_BUF_INTF_VBATLF)
+			tmp |= RTC_VL_BACKUP_LOW;
+
+		return put_user(tmp, (unsigned int __user *)arg);
+	default:
+		return -ENOIOCTLCMD;
+	}
+	return ret;
+}
+#else
+#define rx8901_ioctl NULL
+#endif
+
 static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 {
 	struct ds1307		*ds1307 = dev_get_drvdata(dev);
@@ -599,10 +635,13 @@ static u8 do_trickle_setup_rx8130(struct ds1307 *ds1307, u32 ohms, bool diode)
 	return setup;
 }
 
-static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms, bool diode)
+static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms __always_unused, bool diode)
 {
-	/* make sure that the backup battery is enabled */
-	u8 setup = RX8901_REG_PWSW_CFG_INIEN;
+	/*
+	 * make sure that the backup battery is enabled and that battery
+	 * voltage detection is performed
+	 */
+	u8 setup = RX8901_REG_PWSW_CFG_INIEN | RX8901_REG_PWSW_CFG_VBATLDETEN;
 
 	if (diode)
 		setup |= RX8901_REG_PWSW_CFG_CHGEN;
@@ -1005,6 +1044,7 @@ static const struct rtc_class_ops rx8130_rtc_ops = {
 static const struct rtc_class_ops rx8901_rtc_ops = {
 	.read_time      = ds1307_get_time,
 	.set_time       = ds1307_set_time,
+	.ioctl          = rx8901_ioctl,
 };
 
 static const struct rtc_class_ops mcp794xx_rtc_ops = {

-- 
2.43.0

Re: [PATCH 4/4] rtc: ds1307: Add support for reading RX8901CE battery VL status

Posted by Alexandre Belloni 1 week, 2 days ago

On 19/12/2025 13:10:38+0100, Fredrik M Olsson wrote:
> Adds support for:
> - Reading the battery voltage low status using the RTC_VL_READ ioctl,
>   which also reports invalid time information if the VLF flag is set.
> 
> Signed-off-by: Fredrik M Olsson <fredrik.m.olsson@axis.com>
> ---
>  drivers/rtc/rtc-ds1307.c | 46 +++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 43 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 99d95e520108..ca062ed0c867 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -133,8 +133,11 @@ enum ds_type {
>  #define RX8901_REG_INTF			0x0e
>  #define RX8901_REG_INTF_VLF		BIT(1)
>  #define RX8901_REG_PWSW_CFG		0x37
> +#define RX8901_REG_PWSW_CFG_VBATLDETEN	BIT(4)
>  #define RX8901_REG_PWSW_CFG_INIEN	BIT(6)
>  #define RX8901_REG_PWSW_CFG_CHGEN	BIT(7)
> +#define RX8901_REG_BUF_INTF		0x46
> +#define RX8901_REG_BUF_INTF_VBATLF	BIT(3)
>  
>  #define MCP794XX_REG_CONTROL		0x07
>  #	define MCP794XX_BIT_ALM0_EN	0x10
> @@ -458,6 +461,39 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_RTC_INTF_DEV
> +static int rx8901_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
> +{
> +	struct ds1307 *ds1307 = dev_get_drvdata(dev);
> +	unsigned int regflag, tmp = 0;
> +	int ret = 0;
> +
> +	switch (cmd) {
> +	case RTC_VL_READ:
> +		ret = regmap_read(ds1307->regmap, RX8901_REG_INTF, &regflag);
> +		if (ret)
> +			return ret;
> +
> +		if (regflag & RX8901_REG_INTF_VLF)
> +			tmp |= RTC_VL_DATA_INVALID;
> +
> +		ret = regmap_read(ds1307->regmap, RX8901_REG_BUF_INTF, &regflag);
> +		if (ret)
> +			return ret;
> +
> +		if (regflag & RX8901_REG_BUF_INTF_VBATLF)
> +			tmp |= RTC_VL_BACKUP_LOW;
> +
> +		return put_user(tmp, (unsigned int __user *)arg);
> +	default:
> +		return -ENOIOCTLCMD;
> +	}
> +	return ret;
> +}
> +#else
> +#define rx8901_ioctl NULL
> +#endif
> +
>  static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
>  {
>  	struct ds1307		*ds1307 = dev_get_drvdata(dev);
> @@ -599,10 +635,13 @@ static u8 do_trickle_setup_rx8130(struct ds1307 *ds1307, u32 ohms, bool diode)
>  	return setup;
>  }
>  
> -static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms, bool diode)
> +static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms __always_unused, bool diode)
>  {
> -	/* make sure that the backup battery is enabled */
> -	u8 setup = RX8901_REG_PWSW_CFG_INIEN;
> +	/*
> +	 * make sure that the backup battery is enabled and that battery
> +	 * voltage detection is performed
> +	 */
> +	u8 setup = RX8901_REG_PWSW_CFG_INIEN | RX8901_REG_PWSW_CFG_VBATLDETEN;
>  
>  	if (diode)
>  		setup |= RX8901_REG_PWSW_CFG_CHGEN;
> @@ -1005,6 +1044,7 @@ static const struct rtc_class_ops rx8130_rtc_ops = {
>  static const struct rtc_class_ops rx8901_rtc_ops = {
>  	.read_time      = ds1307_get_time,
>  	.set_time       = ds1307_set_time,
> +	.ioctl          = rx8901_ioctl,
>  };
>  

This seems to be an unrelated changed that hasn't been squashed in the
proper patch.


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

Re: [PATCH 4/4] rtc: ds1307: Add support for reading RX8901CE battery VL status

Posted by Fredrik M Olsson 5 days, 23 hours ago

On 1/31/26 01:05, Alexandre Belloni wrote:
> [Some people who received this message don't often get email from alexandre.belloni@bootlin.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On 19/12/2025 13:10:38+0100, Fredrik M Olsson wrote:
>> Adds support for:
>> - Reading the battery voltage low status using the RTC_VL_READ ioctl,
>>    which also reports invalid time information if the VLF flag is set.
>>
>> Signed-off-by: Fredrik M Olsson <fredrik.m.olsson@axis.com>
>> ---
>>   drivers/rtc/rtc-ds1307.c | 46 +++++++++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 43 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
>> index 99d95e520108..ca062ed0c867 100644
>> --- a/drivers/rtc/rtc-ds1307.c
>> +++ b/drivers/rtc/rtc-ds1307.c
>> @@ -133,8 +133,11 @@ enum ds_type {
>>   #define RX8901_REG_INTF                      0x0e
>>   #define RX8901_REG_INTF_VLF          BIT(1)
>>   #define RX8901_REG_PWSW_CFG          0x37
>> +#define RX8901_REG_PWSW_CFG_VBATLDETEN       BIT(4)
>>   #define RX8901_REG_PWSW_CFG_INIEN    BIT(6)
>>   #define RX8901_REG_PWSW_CFG_CHGEN    BIT(7)
>> +#define RX8901_REG_BUF_INTF          0x46
>> +#define RX8901_REG_BUF_INTF_VBATLF   BIT(3)
>>
>>   #define MCP794XX_REG_CONTROL         0x07
>>   #    define MCP794XX_BIT_ALM0_EN     0x10
>> @@ -458,6 +461,39 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
>>        return 0;
>>   }
>>
>> +#ifdef CONFIG_RTC_INTF_DEV
>> +static int rx8901_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
>> +{
>> +     struct ds1307 *ds1307 = dev_get_drvdata(dev);
>> +     unsigned int regflag, tmp = 0;
>> +     int ret = 0;
>> +
>> +     switch (cmd) {
>> +     case RTC_VL_READ:
>> +             ret = regmap_read(ds1307->regmap, RX8901_REG_INTF, &regflag);
>> +             if (ret)
>> +                     return ret;
>> +
>> +             if (regflag & RX8901_REG_INTF_VLF)
>> +                     tmp |= RTC_VL_DATA_INVALID;
>> +
>> +             ret = regmap_read(ds1307->regmap, RX8901_REG_BUF_INTF, &regflag);
>> +             if (ret)
>> +                     return ret;
>> +
>> +             if (regflag & RX8901_REG_BUF_INTF_VBATLF)
>> +                     tmp |= RTC_VL_BACKUP_LOW;
>> +
>> +             return put_user(tmp, (unsigned int __user *)arg);
>> +     default:
>> +             return -ENOIOCTLCMD;
>> +     }
>> +     return ret;
>> +}
>> +#else
>> +#define rx8901_ioctl NULL
>> +#endif
>> +
>>   static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
>>   {
>>        struct ds1307           *ds1307 = dev_get_drvdata(dev);
>> @@ -599,10 +635,13 @@ static u8 do_trickle_setup_rx8130(struct ds1307 *ds1307, u32 ohms, bool diode)
>>        return setup;
>>   }
>>
>> -static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms, bool diode)
>> +static u8 do_trickle_setup_rx8901(struct ds1307 *ds1307, u32 ohms __always_unused, bool diode)
>>   {
>> -     /* make sure that the backup battery is enabled */
>> -     u8 setup = RX8901_REG_PWSW_CFG_INIEN;
>> +     /*
>> +      * make sure that the backup battery is enabled and that battery
>> +      * voltage detection is performed
>> +      */
>> +     u8 setup = RX8901_REG_PWSW_CFG_INIEN | RX8901_REG_PWSW_CFG_VBATLDETEN;
>>
>>        if (diode)
>>                setup |= RX8901_REG_PWSW_CFG_CHGEN;
>> @@ -1005,6 +1044,7 @@ static const struct rtc_class_ops rx8130_rtc_ops = {
>>   static const struct rtc_class_ops rx8901_rtc_ops = {
>>        .read_time      = ds1307_get_time,
>>        .set_time       = ds1307_set_time,
>> +     .ioctl          = rx8901_ioctl,
>>   };
>>
> 
> This seems to be an unrelated changed that hasn't been squashed in the
> proper patch.
> 

Okay I will squash this change into patch 3 for v2.

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


-- 
/Fredrik

[PATCH 1/4] dt-bindings: rtc: ds1307: Add epson,rx8901
[PATCH 2/4] rtc: ds1307: Fix off-by-one issue with wday for rx8130
[PATCH 3/4] rtc: ds1307: Add Driver for Epson RX8901CE
[PATCH 4/4] rtc: ds1307: Add support for reading RX8901CE battery VL status