[PATCH v4 1/2] dt-bindings: rtc: max31335: add max31335 bindings

[PATCH v4 1/2] dt-bindings: rtc: max31335: add max31335 bindings

[Antoniu Miclaus]

Document the Analog Devices MAX31335 device tree bindings.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
changes in v4:
 - drop `aux-voltage-chargeable` since it comes with rtc.yaml
 .../devicetree/bindings/rtc/adi,max31335.yaml | 62 +++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rtc/adi,max31335.yaml

diff --git a/Documentation/devicetree/bindings/rtc/adi,max31335.yaml b/Documentation/devicetree/bindings/rtc/adi,max31335.yaml
new file mode 100644
index 000000000000..34cc87b92c02
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/adi,max31335.yaml
@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/adi,max31335.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX31335 RTC
+
+maintainers:
+  - Antoniu Miclaus <antoniu.miclaus@analog.com>
+
+description:
+  Analog Devices MAX31335 I2C RTC ±2ppm Automotive Real-Time Clock with
+  Integrated MEMS Resonator.
+
+allOf:
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    const: adi,max31335
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  "#clock-cells":
+    description:
+      RTC can be used as a clock source through its clock output pin.
+    const: 0
+
+  trickle-resistor-ohms:
+    description:
+      Selected resistor for trickle charger. Should be specified if trickle
+      charger should be enabled.
+    enum: [3000, 6000, 11000]
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        rtc@68 {
+            compatible = "adi,max31335";
+            reg = <0x68>;
+            pinctrl-0 = <&rtc_nint_pins>;
+            interrupts-extended = <&gpio1 16 IRQ_TYPE_LEVEL_HIGH>;
+            trickle-resistor-ohms = <6000>;
+            aux-voltage-chargeable =<1>;
+        };
+    };
+...
-- 
2.42.0

[PATCH v4 2/2] rtc: max31335: add driver support

[Antoniu Miclaus]

RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
Integrated MEMS Resonator.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
changes in v4:
 - add Kconfig entry for HWMON dependency.
 MAINTAINERS                |   8 +
 drivers/rtc/Kconfig        |  20 +
 drivers/rtc/Makefile       |   1 +
 drivers/rtc/rtc-max31335.c | 765 +++++++++++++++++++++++++++++++++++++
 4 files changed, 794 insertions(+)
 create mode 100644 drivers/rtc/rtc-max31335.c

diff --git a/MAINTAINERS b/MAINTAINERS
index dd5de540ec0b..bc484cb997ab 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12823,6 +12823,14 @@ F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
 F:	Documentation/hwmon/max31827.rst
 F:	drivers/hwmon/max31827.c
 
+MAX31335 RTC DRIVER
+M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
+L:	linux-rtc@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/rtc/adi,max31335.yaml
+F:	drivers/rtc/rtc-max31335.c
+
 MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
 L:	linux-hwmon@vger.kernel.org
 S:	Orphan
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index d7502433c78a..360da13fe61b 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -373,6 +373,26 @@ config RTC_DRV_MAX8997
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-max8997.
 
+config RTC_DRV_MAX31335
+	tristate "Analog Devices MAX31335"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for the Analog Devices
+	  MAX31335.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-max31335.
+
+config RTC_DRV_MAX31335_HWMON
+	bool "HWMON support for Analog Devices MAX31335"
+	depends on RTC_DRV_MAX31335 && HWMON
+	depends on !(RTC_DRV_MAX31335=y && HWMON=m)
+	default y
+	help
+	  Say Y here if you want to expose temperature sensor data on
+	  rtc-max31335.
+
 config RTC_DRV_MAX77686
 	tristate "Maxim MAX77686"
 	depends on MFD_MAX77686 || MFD_MAX77620 || MFD_MAX77714 || COMPILE_TEST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index fd209883ee2e..99e683a48240 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -88,6 +88,7 @@ obj-$(CONFIG_RTC_DRV_M41T94)	+= rtc-m41t94.o
 obj-$(CONFIG_RTC_DRV_M48T35)	+= rtc-m48t35.o
 obj-$(CONFIG_RTC_DRV_M48T59)	+= rtc-m48t59.o
 obj-$(CONFIG_RTC_DRV_M48T86)	+= rtc-m48t86.o
+obj-$(CONFIG_RTC_DRV_MAX31335)	+= rtc-max31335.o
 obj-$(CONFIG_RTC_DRV_MAX6900)	+= rtc-max6900.o
 obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o
 obj-$(CONFIG_RTC_DRV_MAX6916)	+= rtc-max6916.o
diff --git a/drivers/rtc/rtc-max31335.c b/drivers/rtc/rtc-max31335.c
new file mode 100644
index 000000000000..b58ff2fcc98a
--- /dev/null
+++ b/drivers/rtc/rtc-max31335.c
@@ -0,0 +1,765 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC driver for the MAX31335
+ *
+ * Copyright (C) 2023 Analog Devices
+ *
+ * Antoniu Miclaus <antoniu.miclaus@analog.com>
+ *
+ */
+
+#include <asm-generic/unaligned.h>
+#include <linux/bcd.h>
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/util_macros.h>
+
+/* MAX31335 Register Map */
+#define MAX31335_STATUS1			0x00
+#define MAX31335_INT_EN1			0x01
+#define MAX31335_STATUS2			0x02
+#define MAX31335_INT_EN2			0x03
+#define MAX31335_RTC_RESET			0x04
+#define MAX31335_RTC_CONFIG			0x05
+#define MAX31335_RTC_CONFIG2			0x06
+#define MAX31335_TIMESTAMP_CONFIG		0x07
+#define MAX31335_TIMER_CONFIG			0x08
+#define MAX31335_SECONDS_1_128			0x09
+#define MAX31335_SECONDS			0x0A
+#define MAX31335_MINUTES			0x0B
+#define MAX31335_HOURS				0x0C
+#define MAX31335_DAY				0x0D
+#define MAX31335_DATE				0x0E
+#define MAX31335_MONTH				0x0F
+#define MAX31335_YEAR				0x0F
+#define MAX31335_ALM1_SEC			0x11
+#define MAX31335_ALM1_MIN			0x12
+#define MAX31335_ALM1_HRS			0x13
+#define MAX31335_ALM1_DAY_DATE			0x14
+#define MAX31335_ALM1_MON			0x15
+#define MAX31335_ALM1_YEAR			0x16
+#define MAX31335_ALM2_MIN			0x17
+#define MAX31335_ALM2_HRS			0x18
+#define MAX31335_ALM2_DAY_DATE			0x19
+#define MAX31335_TIMER_COUNT			0x1A
+#define MAX31335_TIMER_INIT			0x1B
+#define MAX31335_PWR_MGMT			0x1C
+#define MAX31335_TRICKLE_REG			0x1D
+#define MAX31335_AGING_OFFSET			0x1E
+#define MAX31335_TS_CONFIG			0x30
+#define MAX31335_TEMP_ALARM_HIGH_MSB		0x31
+#define MAX31335_TEMP_ALARM_HIGH_LSB		0x32
+#define MAX31335_TEMP_ALARM_LOW_MSB		0x33
+#define MAX31335_TEMP_ALARM_LOW_LSB		0x34
+#define MAX31335_TEMP_DATA_MSB			0x35
+#define MAX31335_TEMP_DATA_LSB			0x36
+#define MAX31335_TS0_SEC_1_128			0x40
+#define MAX31335_TS0_SEC			0x41
+#define MAX31335_TS0_MIN			0x42
+#define MAX31335_TS0_HOUR			0x43
+#define MAX31335_TS0_DATE			0x44
+#define MAX31335_TS0_MONTH			0x45
+#define MAX31335_TS0_YEAR			0x46
+#define MAX31335_TS0_FLAGS			0x47
+#define MAX31335_TS1_SEC_1_128			0x48
+#define MAX31335_TS1_SEC			0x49
+#define MAX31335_TS1_MIN			0x4A
+#define MAX31335_TS1_HOUR			0x4B
+#define MAX31335_TS1_DATE			0x4C
+#define MAX31335_TS1_MONTH			0x4D
+#define MAX31335_TS1_YEAR			0x4E
+#define MAX31335_TS1_FLAGS			0x4F
+#define MAX31335_TS2_SEC_1_128			0x50
+#define MAX31335_TS2_SEC			0x51
+#define MAX31335_TS2_MIN			0x52
+#define MAX31335_TS2_HOUR			0x53
+#define MAX31335_TS2_DATE			0x54
+#define MAX31335_TS2_MONTH			0x55
+#define MAX31335_TS2_YEAR			0x56
+#define MAX31335_TS2_FLAGS			0x57
+#define MAX31335_TS3_SEC_1_128			0x58
+#define MAX31335_TS3_SEC			0x59
+#define MAX31335_TS3_MIN			0x5A
+#define MAX31335_TS3_HOUR			0x5B
+#define MAX31335_TS3_DATE			0x5C
+#define MAX31335_TS3_MONTH			0x5D
+#define MAX31335_TS3_YEAR			0x5E
+#define MAX31335_TS3_FLAGS			0x5F
+
+/* MAX31335_STATUS1 Bit Definitions */
+#define MAX31335_STATUS1_PSDECT			BIT(7)
+#define MAX31335_STATUS1_OSF			BIT(6)
+#define MAX31335_STATUS1_PFAIL			BIT(5)
+#define MAX31335_STATUS1_VBATLOW		BIT(4)
+#define MAX31335_STATUS1_DIF			BIT(3)
+#define MAX31335_STATUS1_TIF			BIT(2)
+#define MAX31335_STATUS1_A2F			BIT(1)
+#define MAX31335_STATUS1_A1F			BIT(0)
+
+/* MAX31335_INT_EN1 Bit Definitions */
+#define MAX31335_INT_EN1_DOSF			BIT(6)
+#define MAX31335_INT_EN1_PFAILE			BIT(5)
+#define MAX31335_INT_EN1_VBATLOWE		BIT(4)
+#define MAX31335_INT_EN1_DIE			BIT(3)
+#define MAX31335_INT_EN1_TIE			BIT(2)
+#define MAX31335_INT_EN1_A2IE			BIT(1)
+#define MAX31335_INT_EN1_A1IE			BIT(0)
+
+/* MAX31335_STATUS2 Bit Definitions */
+#define MAX31335_STATUS2_TEMP_RDY		BIT(2)
+#define MAX31335_STATUS2_OTF			BIT(1)
+#define MAX31335_STATUS2_UTF			BIT(0)
+
+/* MAX31335_INT_EN2 Bit Definitions */
+#define MAX31335_INT_EN2_TEMP_RDY_EN		BIT(2)
+#define MAX31335_INT_EN2_OTIE			BIT(1)
+#define MAX31335_INT_EN2_UTIE			BIT(0)
+
+/* MAX31335_RTC_RESET Bit Definitions */
+#define MAX31335_RTC_RESET_SWRST		BIT(0)
+
+/* MAX31335_RTC_CONFIG1 Bit Definitions */
+#define MAX31335_RTC_CONFIG1_EN_IO		BIT(6)
+#define MAX31335_RTC_CONFIG1_A1AC		GENMASK(5, 4)
+#define MAX31335_RTC_CONFIG1_DIP		BIT(3)
+#define MAX31335_RTC_CONFIG1_I2C_TIMEOUT	BIT(1)
+#define MAX31335_RTC_CONFIG1_EN_OSC		BIT(0)
+
+/* MAX31335_RTC_CONFIG2 Bit Definitions */
+#define MAX31335_RTC_CONFIG2_ENCLKO		BIT(2)
+#define MAX31335_RTC_CONFIG2_CLKO_HZ		GENMASK(1, 0)
+
+/* MAX31335_TIMESTAMP_CONFIG Bit Definitions */
+#define MAX31335_TIMESTAMP_CONFIG_TSVLOW	BIT(5)
+#define MAX31335_TIMESTAMP_CONFIG_TSPWM		BIT(4)
+#define MAX31335_TIMESTAMP_CONFIG_TSDIN		BIT(3)
+#define MAX31335_TIMESTAMP_CONFIG_TSOW		BIT(2)
+#define MAX31335_TIMESTAMP_CONFIG_TSR		BIT(1)
+#define MAX31335_TIMESTAMP_CONFIG_TSE		BIT(0)
+
+/* MAX31335_TIMER_CONFIG Bit Definitions */
+#define MAX31335_TIMER_CONFIG_TE		BIT(4)
+#define MAX31335_TIMER_CONFIG_TPAUSE		BIT(3)
+#define MAX31335_TIMER_CONFIG_TRPT		BIT(2)
+#define MAX31335_TIMER_CONFIG_TFS		GENMASK(1, 0)
+
+/* MAX31335_HOURS Bit Definitions */
+#define MAX31335_HOURS_F_24_12			BIT(6)
+#define MAX31335_HOURS_HR_20_AM_PM		BIT(5)
+
+/* MAX31335_MONTH Bit Definitions */
+#define MAX31335_MONTH_CENTURY			BIT(7)
+
+/* MAX31335_PWR_MGMT Bit Definitions */
+#define MAX31335_PWR_MGMT_PFVT			BIT(0)
+
+/* MAX31335_TRICKLE_REG Bit Definitions */
+#define MAX31335_TRICKLE_REG_TRICKLE		GENMASK(3, 1)
+#define MAX31335_TRICKLE_REG_EN_TRICKLE		BIT(0)
+
+/* MAX31335_TS_CONFIG Bit Definitions */
+#define MAX31335_TS_CONFIG_AUTO			BIT(4)
+#define MAX31335_TS_CONFIG_CONVERT_T		BIT(3)
+#define MAX31335_TS_CONFIG_TSINT		GENMASK(2, 0)
+
+/* MAX31335_TS_FLAGS Bit Definitions */
+#define MAX31335_TS_FLAGS_VLOWF			BIT(3)
+#define MAX31335_TS_FLAGS_VBATF			BIT(2)
+#define MAX31335_TS_FLAGS_VCCF			BIT(1)
+#define MAX31335_TS_FLAGS_DINF			BIT(0)
+
+/* MAX31335 Miscellaneous Definitions */
+#define MAX31335_RAM_SIZE			32
+#define MAX31335_TIME_SIZE			0x07
+
+#define clk_hw_to_max31335(_hw) container_of(_hw, struct max31335_data, clkout)
+
+struct max31335_data {
+	struct regmap *regmap;
+	struct rtc_device *rtc;
+	struct clk_hw clkout;
+};
+
+static const int max31335_clkout_freq[] = { 1, 64, 1024, 32768 };
+
+static const u16 max31335_trickle_resistors[] = {3000, 6000, 11000};
+
+static bool max31335_volatile_reg(struct device *dev, unsigned int reg)
+{
+	/* time keeping registers */
+	if (reg >= MAX31335_SECONDS &&
+	    reg < MAX31335_SECONDS + MAX31335_TIME_SIZE)
+		return true;
+
+	/* interrupt status register */
+	if (reg == MAX31335_INT_EN1_A1IE)
+		return true;
+
+	/* temperature registers */
+	if (reg == MAX31335_TEMP_DATA_MSB || MAX31335_TEMP_DATA_LSB)
+		return true;
+
+	return false;
+}
+
+static const struct regmap_config regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x5F,
+	.volatile_reg = max31335_volatile_reg,
+};
+
+static int max31335_get_hour(u8 hour_reg)
+{
+	int hour;
+
+	/* 24Hr mode */
+	if (!FIELD_GET(MAX31335_HOURS_F_24_12, hour_reg))
+		return bcd2bin(hour_reg & 0x3f);
+
+	/* 12Hr mode */
+	hour = bcd2bin(hour_reg & 0x1f);
+	if (hour == 12)
+		hour = 0;
+
+	if (FIELD_GET(MAX31335_HOURS_HR_20_AM_PM, hour_reg))
+		hour += 12;
+
+	return hour;
+}
+
+static int max31335_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	u8 date[7];
+	int ret;
+
+	ret = regmap_bulk_read(max31335->regmap, MAX31335_SECONDS, date,
+			       sizeof(date));
+	if (ret)
+		return ret;
+
+	tm->tm_sec  = bcd2bin(date[0] & 0x7f);
+	tm->tm_min  = bcd2bin(date[1] & 0x7f);
+	tm->tm_hour = max31335_get_hour(date[2]);
+	tm->tm_wday = bcd2bin(date[3] & 0x7) - 1;
+	tm->tm_mday = bcd2bin(date[4] & 0x3f);
+	tm->tm_mon  = bcd2bin(date[5] & 0x1f) - 1;
+	tm->tm_year = bcd2bin(date[6]) + 100;
+
+	if (FIELD_GET(MAX31335_MONTH_CENTURY, date[5]))
+		tm->tm_year += 100;
+
+	return 0;
+}
+
+static int max31335_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	u8 date[7];
+
+	date[0] = bin2bcd(tm->tm_sec);
+	date[1] = bin2bcd(tm->tm_min);
+	date[2] = bin2bcd(tm->tm_hour);
+	date[3] = bin2bcd(tm->tm_wday + 1);
+	date[4] = bin2bcd(tm->tm_mday);
+	date[5] = bin2bcd(tm->tm_mon + 1);
+	date[6] = bin2bcd(tm->tm_year % 100);
+
+	if (tm->tm_year >= 200)
+		date[5] |= FIELD_PREP(MAX31335_MONTH_CENTURY, 1);
+
+	return regmap_bulk_write(max31335->regmap, MAX31335_SECONDS, date,
+				 sizeof(date));
+}
+
+static int max31335_read_offset(struct device *dev, long *offset)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	u32 value;
+	int ret;
+
+	ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET, &value);
+	if (ret)
+		return ret;
+
+	*offset = value;
+
+	return 0;
+}
+
+static int max31335_set_offset(struct device *dev, long offset)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+
+	return regmap_write(max31335->regmap, MAX31335_AGING_OFFSET, offset);
+}
+
+static int max31335_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	struct mutex *lock = &max31335->rtc->ops_lock;
+	int ret, ctrl, status;
+	struct rtc_time time;
+	u8 regs[6];
+
+	mutex_lock(lock);
+
+	ret = regmap_bulk_read(max31335->regmap, MAX31335_ALM1_SEC, regs,
+			       sizeof(regs));
+	if (ret)
+		goto exit;
+
+	alrm->time.tm_sec  = bcd2bin(regs[0] & 0x7f);
+	alrm->time.tm_min  = bcd2bin(regs[1] & 0x7f);
+	alrm->time.tm_hour = bcd2bin(regs[2] & 0x3f);
+	alrm->time.tm_mday = bcd2bin(regs[3] & 0x3f);
+	alrm->time.tm_mon  = bcd2bin(regs[4] & 0x1f) - 1;
+	alrm->time.tm_year = bcd2bin(regs[5]) + 100;
+
+	ret = max31335_read_time(dev, &time);
+	if (ret)
+		goto exit;
+
+	if (time.tm_year >= 200)
+		alrm->time.tm_year += 100;
+
+	ret = regmap_read(max31335->regmap, MAX31335_INT_EN1, &ctrl);
+	if (ret)
+		goto exit;
+
+	ret = regmap_read(max31335->regmap, MAX31335_STATUS1, &status);
+	if (ret)
+		goto exit;
+
+	alrm->enabled = FIELD_GET(MAX31335_INT_EN1_A1IE, ctrl);
+	alrm->pending = FIELD_GET(MAX31335_STATUS1_A1F, status);
+
+exit:
+	mutex_unlock(lock);
+
+	return ret;
+}
+
+static int max31335_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	struct mutex *lock = &max31335->rtc->ops_lock;
+	unsigned int reg;
+	u8 regs[6];
+	int ret;
+
+	regs[0] = bin2bcd(alrm->time.tm_sec);
+	regs[1] = bin2bcd(alrm->time.tm_min);
+	regs[2] = bin2bcd(alrm->time.tm_hour);
+	regs[3] = bin2bcd(alrm->time.tm_mday);
+	regs[4] = bin2bcd(alrm->time.tm_mon + 1);
+	regs[5] = bin2bcd(alrm->time.tm_year % 100);
+
+	mutex_lock(lock);
+
+	ret = regmap_bulk_write(max31335->regmap, MAX31335_ALM1_SEC,
+				regs, sizeof(regs));
+	if (ret)
+		goto exit;
+
+	reg = FIELD_PREP(MAX31335_INT_EN1_A1IE, alrm->enabled);
+	ret = regmap_update_bits(max31335->regmap, MAX31335_INT_EN1,
+				 MAX31335_INT_EN1_A1IE, reg);
+	if (ret)
+		goto exit;
+
+	ret = regmap_update_bits(max31335->regmap, MAX31335_STATUS1,
+				 MAX31335_STATUS1_A1F, 0);
+
+exit:
+	mutex_unlock(lock);
+
+	return ret;
+}
+
+static int max31335_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+
+	return regmap_update_bits(max31335->regmap, MAX31335_INT_EN1,
+				  MAX31335_INT_EN1_A1IE, enabled);
+}
+
+static irqreturn_t max31335_handle_irq(int irq, void *dev_id)
+{
+	struct max31335_data *max31335 = dev_id;
+	struct mutex *lock = &max31335->rtc->ops_lock;
+	int ret, status;
+
+	mutex_lock(lock);
+
+	ret = regmap_read(max31335->regmap, MAX31335_STATUS1, &status);
+	if (ret)
+		goto exit;
+
+	if (FIELD_GET(MAX31335_STATUS1_A1F, status)) {
+		ret = regmap_update_bits(max31335->regmap, MAX31335_STATUS1,
+					 MAX31335_STATUS1_A1F, 0);
+		if (ret)
+			goto exit;
+
+		rtc_update_irq(max31335->rtc, 1, RTC_AF | RTC_IRQF);
+	}
+
+exit:
+	mutex_unlock(lock);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops max31335_rtc_ops = {
+	.read_time = max31335_read_time,
+	.set_time = max31335_set_time,
+	.read_offset = max31335_read_offset,
+	.set_offset = max31335_set_offset,
+	.read_alarm = max31335_read_alarm,
+	.set_alarm = max31335_set_alarm,
+	.alarm_irq_enable = max31335_alarm_irq_enable,
+};
+
+static int max31335_trickle_charger_setup(struct device *dev,
+					  struct max31335_data *max31335)
+{
+	u32 ohms, chargeable;
+	bool diode = false;
+	int i;
+
+	if (device_property_read_u32(dev, "trickle-resistor-ohms", &ohms))
+		return 0;
+
+	if (!device_property_read_u32(dev, "aux-voltage-chargeable",
+				      &chargeable)) {
+		switch (chargeable) {
+		case 0:
+			diode = false;
+			break;
+		case 1:
+			diode = true;
+			break;
+		default:
+			dev_warn(dev,
+				 "unsupported aux-voltage-chargeable value\n");
+			break;
+		}
+	}
+
+	for (i = 0; i < ARRAY_SIZE(max31335_trickle_resistors); i++)
+		if (ohms == max31335_trickle_resistors[i])
+			break;
+
+	if (i >= ARRAY_SIZE(max31335_trickle_resistors)) {
+		dev_warn(dev, "invalid trickle resistor value\n");
+
+		return 0;
+	}
+
+	if (diode)
+		i = i + 4;
+	else
+		i = i + 1;
+
+	return regmap_write(max31335->regmap, MAX31335_TRICKLE_REG,
+			    FIELD_PREP(MAX31335_TRICKLE_REG_TRICKLE, i) |
+				       MAX31335_TRICKLE_REG_EN_TRICKLE);
+}
+
+static unsigned long max31335_clkout_recalc_rate(struct clk_hw *hw,
+						 unsigned long parent_rate)
+{
+	struct max31335_data *max31335 = clk_hw_to_max31335(hw);
+	unsigned int freq_mask;
+	unsigned int reg;
+	int ret;
+
+	ret = regmap_read(max31335->regmap, MAX31335_RTC_CONFIG2, &reg);
+	if (ret)
+		return 0;
+
+	freq_mask = __roundup_pow_of_two(ARRAY_SIZE(max31335_clkout_freq)) - 1;
+
+	return max31335_clkout_freq[reg & freq_mask];
+}
+
+static long max31335_clkout_round_rate(struct clk_hw *hw, unsigned long rate,
+				       unsigned long *prate)
+{
+	int index;
+
+	index = find_closest(rate, max31335_clkout_freq,
+			     ARRAY_SIZE(max31335_clkout_freq));
+
+	return max31335_clkout_freq[index];
+}
+
+static int max31335_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
+				    unsigned long parent_rate)
+{
+	struct max31335_data *max31335 = clk_hw_to_max31335(hw);
+	unsigned int freq_mask;
+	int index;
+
+	index = find_closest(rate, max31335_clkout_freq,
+			     ARRAY_SIZE(max31335_clkout_freq));
+	freq_mask = __roundup_pow_of_two(ARRAY_SIZE(max31335_clkout_freq)) - 1;
+
+	return regmap_update_bits(max31335->regmap, MAX31335_RTC_CONFIG2,
+				  freq_mask, index);
+}
+
+static int max31335_clkout_enable(struct clk_hw *hw)
+{
+	struct max31335_data *max31335 = clk_hw_to_max31335(hw);
+
+	return regmap_set_bits(max31335->regmap, MAX31335_RTC_CONFIG2,
+			       MAX31335_RTC_CONFIG2_ENCLKO);
+}
+
+static void max31335_clkout_disable(struct clk_hw *hw)
+{
+	struct max31335_data *max31335 = clk_hw_to_max31335(hw);
+
+	regmap_clear_bits(max31335->regmap, MAX31335_RTC_CONFIG2,
+			  MAX31335_RTC_CONFIG2_ENCLKO);
+}
+
+static int max31335_clkout_is_enabled(struct clk_hw *hw)
+{
+	struct max31335_data *max31335 = clk_hw_to_max31335(hw);
+	unsigned int reg;
+	int ret;
+
+	ret = regmap_read(max31335->regmap, MAX31335_RTC_CONFIG2, &reg);
+	if (ret)
+		return ret;
+
+	return !!(reg & MAX31335_RTC_CONFIG2_ENCLKO);
+}
+
+static const struct clk_ops max31335_clkout_ops = {
+	.recalc_rate = max31335_clkout_recalc_rate,
+	.round_rate = max31335_clkout_round_rate,
+	.set_rate = max31335_clkout_set_rate,
+	.enable = max31335_clkout_enable,
+	.disable = max31335_clkout_disable,
+	.is_enabled = max31335_clkout_is_enabled,
+};
+
+struct clk_init_data max31335_clk_init = {
+	.name = "max31335-clkout",
+	.ops = &max31335_clkout_ops,
+};
+
+static int max31335_nvmem_reg_read(void *priv, unsigned int offset,
+				   void *val, size_t bytes)
+{
+	struct max31335_data *max31335 = priv;
+	unsigned int reg = MAX31335_TS0_SEC_1_128 + offset;
+
+	return regmap_bulk_read(max31335->regmap, reg, val, bytes);
+}
+
+static int max31335_nvmem_reg_write(void *priv, unsigned int offset,
+				    void *val, size_t bytes)
+{
+	struct max31335_data *max31335 = priv;
+	unsigned int reg = MAX31335_TS0_SEC_1_128 + offset;
+
+	return regmap_bulk_write(max31335->regmap, reg, val, bytes);
+}
+
+struct nvmem_config max31335_nvmem_cfg = {
+	.reg_read = max31335_nvmem_reg_read,
+	.reg_write = max31335_nvmem_reg_write,
+	.word_size = 8,
+	.size = MAX31335_RAM_SIZE,
+};
+
+static int max31335_read_temp(struct device *dev, enum hwmon_sensor_types type,
+			      u32 attr, int channel, long *val)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	u8 reg[2];
+	s16 temp;
+	int ret;
+
+	if (type != hwmon_temp || attr != hwmon_temp_input)
+		return -EOPNOTSUPP;
+
+	ret = regmap_bulk_read(max31335->regmap, MAX31335_TEMP_DATA_MSB,
+			       reg, 2);
+	if (ret)
+		return ret;
+
+	temp = get_unaligned_be16(reg);
+
+	*val = (temp / 64) * 250;
+
+	return 0;
+}
+
+static umode_t max31335_is_visible(const void *data,
+				   enum hwmon_sensor_types type,
+				   u32 attr, int channel)
+{
+	if (type == hwmon_temp && attr == hwmon_temp_input)
+		return 0444;
+
+	return 0;
+}
+
+static const struct hwmon_channel_info *max31335_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	NULL
+};
+
+static const struct hwmon_ops max31335_hwmon_ops = {
+	.is_visible = max31335_is_visible,
+	.read = max31335_read_temp,
+};
+
+static const struct hwmon_chip_info max31335_chip_info = {
+	.ops = &max31335_hwmon_ops,
+	.info = max31335_info,
+};
+
+static int max31335_clkout_register(struct device *dev)
+{
+	struct max31335_data *max31335 = dev_get_drvdata(dev);
+	int ret;
+
+	if (!device_property_present(dev, "#clock-cells"))
+		return 0;
+
+	max31335->clkout.init = &max31335_clk_init;
+
+	ret = devm_clk_hw_register(dev, &max31335->clkout);
+	if (ret)
+		return dev_err_probe(dev, ret, "cannot register clock\n");
+
+	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+					  &max31335->clkout);
+	if (ret)
+		return dev_err_probe(dev, ret, "cannot add hw provider\n");
+
+	max31335->clkout.clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(max31335->clkout.clk))
+		return dev_err_probe(dev, PTR_ERR(max31335->clkout.clk),
+				     "cannot enable clkout\n");
+
+	return 0;
+}
+
+static int max31335_probe(struct i2c_client *client)
+{
+	struct max31335_data *max31335;
+	struct device *hwmon;
+	int ret;
+
+	max31335 = devm_kzalloc(&client->dev, sizeof(*max31335), GFP_KERNEL);
+	if (!max31335)
+		return -ENOMEM;
+
+	max31335->regmap = devm_regmap_init_i2c(client, &regmap_config);
+	if (IS_ERR(max31335->regmap))
+		return PTR_ERR(max31335->regmap);
+
+	i2c_set_clientdata(client, max31335);
+
+	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 1);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 0);
+	if (ret)
+		return ret;
+
+	max31335->rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(max31335->rtc))
+		return PTR_ERR(max31335->rtc);
+
+	max31335->rtc->ops = &max31335_rtc_ops;
+	max31335->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	max31335->rtc->range_max = RTC_TIMESTAMP_END_2199;
+
+	ret = devm_rtc_register_device(max31335->rtc);
+	if (ret)
+		return ret;
+
+	ret = max31335_clkout_register(&client->dev);
+	if (ret)
+		return ret;
+
+	if (client->irq > 0) {
+		ret = devm_request_threaded_irq(&client->dev, client->irq,
+						NULL, max31335_handle_irq,
+						IRQF_ONESHOT,
+						"max31335", max31335);
+		if (ret) {
+			dev_warn(&client->dev,
+				 "unable to request IRQ, alarm max31335 disabled\n");
+			client->irq = 0;
+		}
+	}
+
+	if (!client->irq)
+		clear_bit(RTC_FEATURE_ALARM, max31335->rtc->features);
+
+	max31335_nvmem_cfg.priv = max31335;
+	ret = devm_rtc_nvmem_register(max31335->rtc, &max31335_nvmem_cfg);
+	if (ret)
+		dev_err_probe(&client->dev, ret, "cannot register rtc nvmem\n");
+
+	hwmon = devm_hwmon_device_register_with_info(&client->dev, client->name,
+						     max31335,
+						     &max31335_chip_info,
+						     NULL);
+	if (IS_ERR(hwmon))
+		dev_err_probe(&client->dev, PTR_ERR(hwmon),
+			      "cannot register hwmon device\n");
+
+	return max31335_trickle_charger_setup(&client->dev, max31335);
+}
+
+static const struct i2c_device_id max31335_id[] = {
+	{ "max31335", 0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, max31335_id);
+
+static const struct of_device_id max31335_of_match[] = {
+	{ .compatible = "adi,max31335" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, max31335_of_match);
+
+static struct i2c_driver max31335_driver = {
+	.driver = {
+		.name = "rtc-max31335",
+		.of_match_table = max31335_of_match,
+	},
+	.probe = max31335_probe,
+	.id_table = max31335_id,
+};
+module_i2c_driver(max31335_driver);
+
+MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com>");
+MODULE_DESCRIPTION("MAX31335 RTC driver");
+MODULE_LICENSE("GPL");
-- 
2.42.0

Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Guenter Roeck]

On Wed, Nov 01, 2023 at 11:48:14AM +0200, Antoniu Miclaus wrote:
> RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
> Integrated MEMS Resonator.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> changes in v4:
>  - add Kconfig entry for HWMON dependency.
>  MAINTAINERS                |   8 +
>  drivers/rtc/Kconfig        |  20 +
>  drivers/rtc/Makefile       |   1 +
>  drivers/rtc/rtc-max31335.c | 765 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 794 insertions(+)
>  create mode 100644 drivers/rtc/rtc-max31335.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index dd5de540ec0b..bc484cb997ab 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12823,6 +12823,14 @@ F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
>  F:	Documentation/hwmon/max31827.rst
>  F:	drivers/hwmon/max31827.c
>  
> +MAX31335 RTC DRIVER
> +M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> +L:	linux-rtc@vger.kernel.org
> +S:	Supported
> +W:	https://ez.analog.com/linux-software-drivers
> +F:	Documentation/devicetree/bindings/rtc/adi,max31335.yaml
> +F:	drivers/rtc/rtc-max31335.c
> +
>  MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
>  L:	linux-hwmon@vger.kernel.org
>  S:	Orphan
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index d7502433c78a..360da13fe61b 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -373,6 +373,26 @@ config RTC_DRV_MAX8997
>  	  This driver can also be built as a module. If so, the module
>  	  will be called rtc-max8997.
>  
> +config RTC_DRV_MAX31335
> +	tristate "Analog Devices MAX31335"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  If you say yes here you get support for the Analog Devices
> +	  MAX31335.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rtc-max31335.
> +
> +config RTC_DRV_MAX31335_HWMON
> +	bool "HWMON support for Analog Devices MAX31335"
> +	depends on RTC_DRV_MAX31335 && HWMON
> +	depends on !(RTC_DRV_MAX31335=y && HWMON=m)
> +	default y
> +	help
> +	  Say Y here if you want to expose temperature sensor data on
> +	  rtc-max31335.
> +

This isn't used in the driver. Did you test with HWMON=n ?

Guenter

RE: [PATCH v4 2/2] rtc: max31335: add driver support

[Miclaus, Antoniu]

> On Wed, Nov 01, 2023 at 11:48:14AM +0200, Antoniu Miclaus wrote:
> > RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
> > Integrated MEMS Resonator.
> >
> > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> > ---
> > changes in v4:
> >  - add Kconfig entry for HWMON dependency.
> >  MAINTAINERS                |   8 +
> >  drivers/rtc/Kconfig        |  20 +
> >  drivers/rtc/Makefile       |   1 +
> >  drivers/rtc/rtc-max31335.c | 765
> +++++++++++++++++++++++++++++++++++++
> >  4 files changed, 794 insertions(+)
> >  create mode 100644 drivers/rtc/rtc-max31335.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index dd5de540ec0b..bc484cb997ab 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -12823,6 +12823,14 @@ F:
> 	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> >  F:	Documentation/hwmon/max31827.rst
> >  F:	drivers/hwmon/max31827.c
> >
> > +MAX31335 RTC DRIVER
> > +M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> > +L:	linux-rtc@vger.kernel.org
> > +S:	Supported
> > +W:	https://ez.analog.com/linux-software-drivers
> > +F:	Documentation/devicetree/bindings/rtc/adi,max31335.yaml
> > +F:	drivers/rtc/rtc-max31335.c
> > +
> >  MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
> >  L:	linux-hwmon@vger.kernel.org
> >  S:	Orphan
> > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > index d7502433c78a..360da13fe61b 100644
> > --- a/drivers/rtc/Kconfig
> > +++ b/drivers/rtc/Kconfig
> > @@ -373,6 +373,26 @@ config RTC_DRV_MAX8997
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called rtc-max8997.
> >
> > +config RTC_DRV_MAX31335
> > +	tristate "Analog Devices MAX31335"
> > +	depends on I2C
> > +	select REGMAP_I2C
> > +	help
> > +	  If you say yes here you get support for the Analog Devices
> > +	  MAX31335.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called rtc-max31335.
> > +
> > +config RTC_DRV_MAX31335_HWMON
> > +	bool "HWMON support for Analog Devices MAX31335"
> > +	depends on RTC_DRV_MAX31335 && HWMON
> > +	depends on !(RTC_DRV_MAX31335=y && HWMON=m)
> > +	default y
> > +	help
> > +	  Say Y here if you want to expose temperature sensor data on
> > +	  rtc-max31335.
> > +
> 
> This isn't used in the driver. Did you test with HWMON=n ?
> 

I need to start thinking a bit more out of the box instead of 
taking other driver approaches as being the only way to go. 😊

Will fix in v5.

> Guenter

Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Guenter Roeck]

On 11/1/23 08:21, Miclaus, Antoniu wrote:
>> On Wed, Nov 01, 2023 at 11:48:14AM +0200, Antoniu Miclaus wrote:
>>> RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
>>> Integrated MEMS Resonator.
>>>
>>> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
>>> ---
>>> changes in v4:
>>>   - add Kconfig entry for HWMON dependency.
>>>   MAINTAINERS                |   8 +
>>>   drivers/rtc/Kconfig        |  20 +
>>>   drivers/rtc/Makefile       |   1 +
>>>   drivers/rtc/rtc-max31335.c | 765
>> +++++++++++++++++++++++++++++++++++++
>>>   4 files changed, 794 insertions(+)
>>>   create mode 100644 drivers/rtc/rtc-max31335.c
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index dd5de540ec0b..bc484cb997ab 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -12823,6 +12823,14 @@ F:
>> 	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
>>>   F:	Documentation/hwmon/max31827.rst
>>>   F:	drivers/hwmon/max31827.c
>>>
>>> +MAX31335 RTC DRIVER
>>> +M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
>>> +L:	linux-rtc@vger.kernel.org
>>> +S:	Supported
>>> +W:	https://ez.analog.com/linux-software-drivers
>>> +F:	Documentation/devicetree/bindings/rtc/adi,max31335.yaml
>>> +F:	drivers/rtc/rtc-max31335.c
>>> +
>>>   MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
>>>   L:	linux-hwmon@vger.kernel.org
>>>   S:	Orphan
>>> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
>>> index d7502433c78a..360da13fe61b 100644
>>> --- a/drivers/rtc/Kconfig
>>> +++ b/drivers/rtc/Kconfig
>>> @@ -373,6 +373,26 @@ config RTC_DRV_MAX8997
>>>   	  This driver can also be built as a module. If so, the module
>>>   	  will be called rtc-max8997.
>>>
>>> +config RTC_DRV_MAX31335
>>> +	tristate "Analog Devices MAX31335"
>>> +	depends on I2C
>>> +	select REGMAP_I2C
>>> +	help
>>> +	  If you say yes here you get support for the Analog Devices
>>> +	  MAX31335.
>>> +
>>> +	  This driver can also be built as a module. If so, the module
>>> +	  will be called rtc-max31335.
>>> +
>>> +config RTC_DRV_MAX31335_HWMON
>>> +	bool "HWMON support for Analog Devices MAX31335"
>>> +	depends on RTC_DRV_MAX31335 && HWMON
>>> +	depends on !(RTC_DRV_MAX31335=y && HWMON=m)
>>> +	default y
>>> +	help
>>> +	  Say Y here if you want to expose temperature sensor data on
>>> +	  rtc-max31335.
>>> +
>>
>> This isn't used in the driver. Did you test with HWMON=n ?
>>
> 
> I need to start thinking a bit more out of the box instead of
> taking other driver approaches as being the only way to go. 😊
> 

There are essentially two options: Either the above, or use
	depends on HWMON || HWMON=n
for RTC_DRV_MAX31335.

In both cases, the driver hwmon code has to be surrounded with #if[def].
Depending on your approach, that will be "#ifdef RTC_DRV_MAX31335_HWMON"
or "#if IS_REACHABLE(HWMON)".

You could also use "depends on HWMON" for RTC_DRV_MAX31335 to avoid the
#ifdef in the driver, but that is normally undesirable.

Guenter

Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Alexandre Belloni]

On 01/11/2023 11:48:14+0200, Antoniu Miclaus wrote:
> +static int max31335_get_hour(u8 hour_reg)
> +{
> +	int hour;
> +
> +	/* 24Hr mode */
> +	if (!FIELD_GET(MAX31335_HOURS_F_24_12, hour_reg))
> +		return bcd2bin(hour_reg & 0x3f);
> +
> +	/* 12Hr mode */
> +	hour = bcd2bin(hour_reg & 0x1f);
> +	if (hour == 12)
> +		hour = 0;
> +

Do you really need to support 12h mode?

> +	if (FIELD_GET(MAX31335_HOURS_HR_20_AM_PM, hour_reg))
> +		hour += 12;
> +
> +	return hour;
> +}
> +
> +static int max31335_read_offset(struct device *dev, long *offset)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +	u32 value;
> +	int ret;
> +
> +	ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET, &value);
> +	if (ret)
> +		return ret;
> +
> +	*offset = value;

This is super dubious, what is the unit of MAX31335_AGING_OFFSET ?

> +
> +	return 0;
> +}
> +
> +static int max31335_set_offset(struct device *dev, long offset)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +
> +	return regmap_write(max31335->regmap, MAX31335_AGING_OFFSET, offset);
> +}
> +
> +static int max31335_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +	struct mutex *lock = &max31335->rtc->ops_lock;
> +	int ret, ctrl, status;
> +	struct rtc_time time;
> +	u8 regs[6];
> +
> +	mutex_lock(lock);

Use rtc_lock(), I'm not quite sure why you would need locking here
though.

> +
> +	ret = regmap_bulk_read(max31335->regmap, MAX31335_ALM1_SEC, regs,
> +			       sizeof(regs));
> +	if (ret)
> +		goto exit;
> +
> +	alrm->time.tm_sec  = bcd2bin(regs[0] & 0x7f);
> +	alrm->time.tm_min  = bcd2bin(regs[1] & 0x7f);
> +	alrm->time.tm_hour = bcd2bin(regs[2] & 0x3f);
> +	alrm->time.tm_mday = bcd2bin(regs[3] & 0x3f);
> +	alrm->time.tm_mon  = bcd2bin(regs[4] & 0x1f) - 1;
> +	alrm->time.tm_year = bcd2bin(regs[5]) + 100;
> +
> +	ret = max31335_read_time(dev, &time);
> +	if (ret)
> +		goto exit;
> +
> +	if (time.tm_year >= 200)
> +		alrm->time.tm_year += 100;
> +
> +	ret = regmap_read(max31335->regmap, MAX31335_INT_EN1, &ctrl);
> +	if (ret)
> +		goto exit;
> +
> +	ret = regmap_read(max31335->regmap, MAX31335_STATUS1, &status);
> +	if (ret)
> +		goto exit;
> +
> +	alrm->enabled = FIELD_GET(MAX31335_INT_EN1_A1IE, ctrl);
> +	alrm->pending = FIELD_GET(MAX31335_STATUS1_A1F, status);
> +
> +exit:
> +	mutex_unlock(lock);
> +
> +	return ret;
> +}
> +
> +static int max31335_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +	struct mutex *lock = &max31335->rtc->ops_lock;
> +	unsigned int reg;
> +	u8 regs[6];
> +	int ret;
> +
> +	regs[0] = bin2bcd(alrm->time.tm_sec);
> +	regs[1] = bin2bcd(alrm->time.tm_min);
> +	regs[2] = bin2bcd(alrm->time.tm_hour);
> +	regs[3] = bin2bcd(alrm->time.tm_mday);
> +	regs[4] = bin2bcd(alrm->time.tm_mon + 1);
> +	regs[5] = bin2bcd(alrm->time.tm_year % 100);
> +
> +	mutex_lock(lock);

I'm not sure why you need locking here either, maybe you should simply
disable the alarm first?

> +
> +	ret = regmap_bulk_write(max31335->regmap, MAX31335_ALM1_SEC,
> +				regs, sizeof(regs));
> +	if (ret)
> +		goto exit;
> +
> +	reg = FIELD_PREP(MAX31335_INT_EN1_A1IE, alrm->enabled);
> +	ret = regmap_update_bits(max31335->regmap, MAX31335_INT_EN1,
> +				 MAX31335_INT_EN1_A1IE, reg);
> +	if (ret)
> +		goto exit;
> +
> +	ret = regmap_update_bits(max31335->regmap, MAX31335_STATUS1,
> +				 MAX31335_STATUS1_A1F, 0);
> +
> +exit:
> +	mutex_unlock(lock);
> +
> +	return ret;
> +}
> +
> +static int max31335_alarm_irq_enable(struct device *dev, unsigned int enabled)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +
> +	return regmap_update_bits(max31335->regmap, MAX31335_INT_EN1,
> +				  MAX31335_INT_EN1_A1IE, enabled);
> +}
> +


> +static int max31335_trickle_charger_setup(struct device *dev,
> +					  struct max31335_data *max31335)
> +{
> +	u32 ohms, chargeable;
> +	bool diode = false;
> +	int i;
> +
> +	if (device_property_read_u32(dev, "trickle-resistor-ohms", &ohms))
> +		return 0;
> +
> +	if (!device_property_read_u32(dev, "aux-voltage-chargeable",
> +				      &chargeable)) {
> +		switch (chargeable) {
> +		case 0:
> +			diode = false;
> +			break;
> +		case 1:
> +			diode = true;
> +			break;
> +		default:
> +			dev_warn(dev,
> +				 "unsupported aux-voltage-chargeable value\n");

I don't think the string is necessary, checking the DT should be done at
compile time.

> +			break;
> +		}
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(max31335_trickle_resistors); i++)
> +		if (ohms == max31335_trickle_resistors[i])
> +			break;
> +
> +	if (i >= ARRAY_SIZE(max31335_trickle_resistors)) {
> +		dev_warn(dev, "invalid trickle resistor value\n");

Ditto.

> +
> +		return 0;
> +	}
> +
> +	if (diode)
> +		i = i + 4;
> +	else
> +		i = i + 1;

Do you actually need to configure the trickle charger when there is
nothing to charge?

> +
> +	return regmap_write(max31335->regmap, MAX31335_TRICKLE_REG,
> +			    FIELD_PREP(MAX31335_TRICKLE_REG_TRICKLE, i) |
> +				       MAX31335_TRICKLE_REG_EN_TRICKLE);
> +}
> +
> +static int max31335_clkout_register(struct device *dev)
> +{
> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> +	int ret;
> +
> +	if (!device_property_present(dev, "#clock-cells"))
> +		return 0;

Is the clock output disabled by default?

> +
> +static int max31335_probe(struct i2c_client *client)
> +{
> +	struct max31335_data *max31335;
> +	struct device *hwmon;
> +	int ret;
> +
> +	max31335 = devm_kzalloc(&client->dev, sizeof(*max31335), GFP_KERNEL);
> +	if (!max31335)
> +		return -ENOMEM;
> +
> +	max31335->regmap = devm_regmap_init_i2c(client, &regmap_config);
> +	if (IS_ERR(max31335->regmap))
> +		return PTR_ERR(max31335->regmap);
> +
> +	i2c_set_clientdata(client, max31335);
> +
> +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 1);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 0);
> +	if (ret)
> +		return ret;

What does this register do?

> +
> +	max31335->rtc = devm_rtc_allocate_device(&client->dev);
> +	if (IS_ERR(max31335->rtc))
> +		return PTR_ERR(max31335->rtc);
> +
> +	max31335->rtc->ops = &max31335_rtc_ops;
> +	max31335->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
> +	max31335->rtc->range_max = RTC_TIMESTAMP_END_2199;

Please set alarm_offset_max too.

> +
> +	ret = devm_rtc_register_device(max31335->rtc);
> +	if (ret)
> +		return ret;
> +
> +	ret = max31335_clkout_register(&client->dev);
> +	if (ret)
> +		return ret;
> +
> +	if (client->irq > 0) {
> +		ret = devm_request_threaded_irq(&client->dev, client->irq,
> +						NULL, max31335_handle_irq,
> +						IRQF_ONESHOT,
> +						"max31335", max31335);
> +		if (ret) {
> +			dev_warn(&client->dev,
> +				 "unable to request IRQ, alarm max31335 disabled\n");
> +			client->irq = 0;
> +		}
> +	}
> +
> +	if (!client->irq)
> +		clear_bit(RTC_FEATURE_ALARM, max31335->rtc->features);
> +
> +	max31335_nvmem_cfg.priv = max31335;
> +	ret = devm_rtc_nvmem_register(max31335->rtc, &max31335_nvmem_cfg);
> +	if (ret)
> +		dev_err_probe(&client->dev, ret, "cannot register rtc nvmem\n");
> +
> +	hwmon = devm_hwmon_device_register_with_info(&client->dev, client->name,
> +						     max31335,
> +						     &max31335_chip_info,
> +						     NULL);
> +	if (IS_ERR(hwmon))
> +		dev_err_probe(&client->dev, PTR_ERR(hwmon),
> +			      "cannot register hwmon device\n");
> +
> +	return max31335_trickle_charger_setup(&client->dev, max31335);

You must never fail probe after calling devm_rtc_register_device, else
you are open to a race condition with userspace.

> +}
> +
> +static const struct i2c_device_id max31335_id[] = {
> +	{ "max31335", 0 },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, max31335_id);
> +
> +static const struct of_device_id max31335_of_match[] = {
> +	{ .compatible = "adi,max31335" },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, max31335_of_match);
> +
> +static struct i2c_driver max31335_driver = {
> +	.driver = {
> +		.name = "rtc-max31335",
> +		.of_match_table = max31335_of_match,
> +	},
> +	.probe = max31335_probe,
> +	.id_table = max31335_id,
> +};
> +module_i2c_driver(max31335_driver);
> +
> +MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com>");
> +MODULE_DESCRIPTION("MAX31335 RTC driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.42.0
> 

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

RE: [PATCH v4 2/2] rtc: max31335: add driver support

[Miclaus, Antoniu]

 
> On 01/11/2023 11:48:14+0200, Antoniu Miclaus wrote:
> > +static int max31335_get_hour(u8 hour_reg)
> > +{
> > +	int hour;
> > +
> > +	/* 24Hr mode */
> > +	if (!FIELD_GET(MAX31335_HOURS_F_24_12, hour_reg))
> > +		return bcd2bin(hour_reg & 0x3f);
> > +
> > +	/* 12Hr mode */
> > +	hour = bcd2bin(hour_reg & 0x1f);
> > +	if (hour == 12)
> > +		hour = 0;
> > +
> 
> Do you really need to support 12h mode?

Is is a feature supported by the part, so I think is nice to have.

> 
> > +	if (FIELD_GET(MAX31335_HOURS_HR_20_AM_PM, hour_reg))
> > +		hour += 12;
> > +
> > +	return hour;
> > +}
> > +
> > +static int max31335_read_offset(struct device *dev, long *offset)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +	u32 value;
> > +	int ret;
> > +
> > +	ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET,
> &value);
> > +	if (ret)
> > +		return ret;
> > +
> > +	*offset = value;
> 
> This is super dubious, what is the unit of MAX31335_AGING_OFFSET ?
> 

There is not additional information on the AGING_OFFSET register (no
other offset registers).
I treated it as a raw value that user can write/read. Should I drop the 
offset implementation?

> > +
> > +	return 0;
> > +}
> > +
> > +static int max31335_set_offset(struct device *dev, long offset)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +
> > +	return regmap_write(max31335->regmap,
> MAX31335_AGING_OFFSET, offset);
> > +}
> > +
> > +static int max31335_read_alarm(struct device *dev, struct rtc_wkalrm
> *alrm)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +	struct mutex *lock = &max31335->rtc->ops_lock;
> > +	int ret, ctrl, status;
> > +	struct rtc_time time;
> > +	u8 regs[6];
> > +
> > +	mutex_lock(lock);
> 
> Use rtc_lock(), I'm not quite sure why you would need locking here
> though.
> 
> > +
> > +	ret = regmap_bulk_read(max31335->regmap,
> MAX31335_ALM1_SEC, regs,
> > +			       sizeof(regs));
> > +	if (ret)
> > +		goto exit;
> > +
> > +	alrm->time.tm_sec  = bcd2bin(regs[0] & 0x7f);
> > +	alrm->time.tm_min  = bcd2bin(regs[1] & 0x7f);
> > +	alrm->time.tm_hour = bcd2bin(regs[2] & 0x3f);
> > +	alrm->time.tm_mday = bcd2bin(regs[3] & 0x3f);
> > +	alrm->time.tm_mon  = bcd2bin(regs[4] & 0x1f) - 1;
> > +	alrm->time.tm_year = bcd2bin(regs[5]) + 100;
> > +
> > +	ret = max31335_read_time(dev, &time);
> > +	if (ret)
> > +		goto exit;
> > +
> > +	if (time.tm_year >= 200)
> > +		alrm->time.tm_year += 100;
> > +
> > +	ret = regmap_read(max31335->regmap, MAX31335_INT_EN1, &ctrl);
> > +	if (ret)
> > +		goto exit;
> > +
> > +	ret = regmap_read(max31335->regmap, MAX31335_STATUS1,
> &status);
> > +	if (ret)
> > +		goto exit;
> > +
> > +	alrm->enabled = FIELD_GET(MAX31335_INT_EN1_A1IE, ctrl);
> > +	alrm->pending = FIELD_GET(MAX31335_STATUS1_A1F, status);
> > +
> > +exit:
> > +	mutex_unlock(lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static int max31335_set_alarm(struct device *dev, struct rtc_wkalrm
> *alrm)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +	struct mutex *lock = &max31335->rtc->ops_lock;
> > +	unsigned int reg;
> > +	u8 regs[6];
> > +	int ret;
> > +
> > +	regs[0] = bin2bcd(alrm->time.tm_sec);
> > +	regs[1] = bin2bcd(alrm->time.tm_min);
> > +	regs[2] = bin2bcd(alrm->time.tm_hour);
> > +	regs[3] = bin2bcd(alrm->time.tm_mday);
> > +	regs[4] = bin2bcd(alrm->time.tm_mon + 1);
> > +	regs[5] = bin2bcd(alrm->time.tm_year % 100);
> > +
> > +	mutex_lock(lock);
> 
> I'm not sure why you need locking here either, maybe you should simply
> disable the alarm first?
> 
> > +
> > +	ret = regmap_bulk_write(max31335->regmap,
> MAX31335_ALM1_SEC,
> > +				regs, sizeof(regs));
> > +	if (ret)
> > +		goto exit;
> > +
> > +	reg = FIELD_PREP(MAX31335_INT_EN1_A1IE, alrm->enabled);
> > +	ret = regmap_update_bits(max31335->regmap,
> MAX31335_INT_EN1,
> > +				 MAX31335_INT_EN1_A1IE, reg);
> > +	if (ret)
> > +		goto exit;
> > +
> > +	ret = regmap_update_bits(max31335->regmap,
> MAX31335_STATUS1,
> > +				 MAX31335_STATUS1_A1F, 0);
> > +
> > +exit:
> > +	mutex_unlock(lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static int max31335_alarm_irq_enable(struct device *dev, unsigned int
> enabled)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +
> > +	return regmap_update_bits(max31335->regmap,
> MAX31335_INT_EN1,
> > +				  MAX31335_INT_EN1_A1IE, enabled);
> > +}
> > +
> 
> 
> > +static int max31335_trickle_charger_setup(struct device *dev,
> > +					  struct max31335_data *max31335)
> > +{
> > +	u32 ohms, chargeable;
> > +	bool diode = false;
> > +	int i;
> > +
> > +	if (device_property_read_u32(dev, "trickle-resistor-ohms", &ohms))
> > +		return 0;
> > +
> > +	if (!device_property_read_u32(dev, "aux-voltage-chargeable",
> > +				      &chargeable)) {
> > +		switch (chargeable) {
> > +		case 0:
> > +			diode = false;
> > +			break;
> > +		case 1:
> > +			diode = true;
> > +			break;
> > +		default:
> > +			dev_warn(dev,
> > +				 "unsupported aux-voltage-chargeable
> value\n");
> 
> I don't think the string is necessary, checking the DT should be done at
> compile time.
> 
> > +			break;
> > +		}
> > +	}
> > +
> > +	for (i = 0; i < ARRAY_SIZE(max31335_trickle_resistors); i++)
> > +		if (ohms == max31335_trickle_resistors[i])
> > +			break;
> > +
> > +	if (i >= ARRAY_SIZE(max31335_trickle_resistors)) {
> > +		dev_warn(dev, "invalid trickle resistor value\n");
> 
> Ditto.
> 
> > +
> > +		return 0;
> > +	}
> > +
> > +	if (diode)
> > +		i = i + 4;
> > +	else
> > +		i = i + 1;
> 
> Do you actually need to configure the trickle charger when there is
> nothing to charge?

These are the options for the trickle chager:
MAX31335_TRICKLE_REG_TRICKLE bits

0x0: 3KΩ in series with a Schottky diode
0x1: 3KΩ in series with a Schottky diode
0x2: 6KΩ in series with a Schottky diode 
0x3: 11KΩ in series with a Schottky diode
0x4: 3KΩ in series with a diode+Schottky diode
0x5: 3KΩ in series with a diode+Schottky diode
0x6: 6KΩ in series with a diode+Schottky diode
0x7: 11KΩ in series with a diode+Schottky diode

> 
> > +
> > +	return regmap_write(max31335->regmap, MAX31335_TRICKLE_REG,
> > +			    FIELD_PREP(MAX31335_TRICKLE_REG_TRICKLE, i) |
> > +				       MAX31335_TRICKLE_REG_EN_TRICKLE);
> > +}
> > +
> > +static int max31335_clkout_register(struct device *dev)
> > +{
> > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > +	int ret;
> > +
> > +	if (!device_property_present(dev, "#clock-cells"))
> > +		return 0;
> 
> Is the clock output disabled by default?

No, I will disable it.

> 
> > +
> > +static int max31335_probe(struct i2c_client *client)
> > +{
> > +	struct max31335_data *max31335;
> > +	struct device *hwmon;
> > +	int ret;
> > +
> > +	max31335 = devm_kzalloc(&client->dev, sizeof(*max31335),
> GFP_KERNEL);
> > +	if (!max31335)
> > +		return -ENOMEM;
> > +
> > +	max31335->regmap = devm_regmap_init_i2c(client,
> &regmap_config);
> > +	if (IS_ERR(max31335->regmap))
> > +		return PTR_ERR(max31335->regmap);
> > +
> > +	i2c_set_clientdata(client, max31335);
> > +
> > +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 1);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 0);
> > +	if (ret)
> > +		return ret;
> 
> What does this register do?
> 

RTC Software Reset Register: 
0x0: Device is in normal mode.
0x1: Resets the digital block and the I2C programmable registers except for
Timestamp/RAM registers and the SWRST bit. Oscillator is disabled.

The bit doesn't clear itself.

> > +
> > +	max31335->rtc = devm_rtc_allocate_device(&client->dev);
> > +	if (IS_ERR(max31335->rtc))
> > +		return PTR_ERR(max31335->rtc);
> > +
> > +	max31335->rtc->ops = &max31335_rtc_ops;
> > +	max31335->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
> > +	max31335->rtc->range_max = RTC_TIMESTAMP_END_2199;
> 
> Please set alarm_offset_max too.
> 
> > +
> > +	ret = devm_rtc_register_device(max31335->rtc);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = max31335_clkout_register(&client->dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (client->irq > 0) {
> > +		ret = devm_request_threaded_irq(&client->dev, client->irq,
> > +						NULL, max31335_handle_irq,
> > +						IRQF_ONESHOT,
> > +						"max31335", max31335);
> > +		if (ret) {
> > +			dev_warn(&client->dev,
> > +				 "unable to request IRQ, alarm max31335
> disabled\n");
> > +			client->irq = 0;
> > +		}
> > +	}
> > +
> > +	if (!client->irq)
> > +		clear_bit(RTC_FEATURE_ALARM, max31335->rtc->features);
> > +
> > +	max31335_nvmem_cfg.priv = max31335;
> > +	ret = devm_rtc_nvmem_register(max31335->rtc,
> &max31335_nvmem_cfg);
> > +	if (ret)
> > +		dev_err_probe(&client->dev, ret, "cannot register rtc
> nvmem\n");
> > +
> > +	hwmon = devm_hwmon_device_register_with_info(&client->dev,
> client->name,
> > +						     max31335,
> > +						     &max31335_chip_info,
> > +						     NULL);
> > +	if (IS_ERR(hwmon))
> > +		dev_err_probe(&client->dev, PTR_ERR(hwmon),
> > +			      "cannot register hwmon device\n");
> > +
> > +	return max31335_trickle_charger_setup(&client->dev, max31335);
> 
> You must never fail probe after calling devm_rtc_register_device, else
> you are open to a race condition with userspace.
> 
> > +}
> > +
> > +static const struct i2c_device_id max31335_id[] = {
> > +	{ "max31335", 0 },
> > +	{ }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(i2c, max31335_id);
> > +
> > +static const struct of_device_id max31335_of_match[] = {
> > +	{ .compatible = "adi,max31335" },
> > +	{ }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(of, max31335_of_match);
> > +
> > +static struct i2c_driver max31335_driver = {
> > +	.driver = {
> > +		.name = "rtc-max31335",
> > +		.of_match_table = max31335_of_match,
> > +	},
> > +	.probe = max31335_probe,
> > +	.id_table = max31335_id,
> > +};
> > +module_i2c_driver(max31335_driver);
> > +
> > +MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com>");
> > +MODULE_DESCRIPTION("MAX31335 RTC driver");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.42.0
> >
> 
> --
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://urldefense.com/v3/__https://bootlin.com__;!!A3Ni8CS0y2Y!9L5oCv
> HC0oT_FwMzkX2RA8fSIOBFPOxEQ_aycnNEcZqpwVS5HKLHl_s1Cji_iNKNHLFI
> Y37QpXsMZUPCyBmurhBxVvwaPVOU$

Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Alexandre Belloni]

On 02/11/2023 13:44:16+0000, Miclaus, Antoniu wrote:
>  
> > On 01/11/2023 11:48:14+0200, Antoniu Miclaus wrote:
> > > +static int max31335_get_hour(u8 hour_reg)
> > > +{
> > > +	int hour;
> > > +
> > > +	/* 24Hr mode */
> > > +	if (!FIELD_GET(MAX31335_HOURS_F_24_12, hour_reg))
> > > +		return bcd2bin(hour_reg & 0x3f);
> > > +
> > > +	/* 12Hr mode */
> > > +	hour = bcd2bin(hour_reg & 0x1f);
> > > +	if (hour == 12)
> > > +		hour = 0;
> > > +
> > 
> > Do you really need to support 12h mode?
> 
> Is is a feature supported by the part, so I think is nice to have.
> 

Is anything on the system going to use it? This driver is not setting
12h time so if there is no other component in the system accessing the
time, there is no chance this is going to be used. Dead code is not nice
to maintain.

> > 
> > > +	if (FIELD_GET(MAX31335_HOURS_HR_20_AM_PM, hour_reg))
> > > +		hour += 12;
> > > +
> > > +	return hour;
> > > +}
> > > +
> > > +static int max31335_read_offset(struct device *dev, long *offset)
> > > +{
> > > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > > +	u32 value;
> > > +	int ret;
> > > +
> > > +	ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET,
> > &value);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	*offset = value;
> > 
> > This is super dubious, what is the unit of MAX31335_AGING_OFFSET ?
> > 
> 
> There is not additional information on the AGING_OFFSET register (no
> other offset registers).
> I treated it as a raw value that user can write/read. Should I drop the 
> offset implementation?
> 

The value exposed to userspace is in parts per billion. If you can't do
the conversion, then you have to drop it.

> > > +
> > > +		return 0;
> > > +	}
> > > +
> > > +	if (diode)
> > > +		i = i + 4;
> > > +	else
> > > +		i = i + 1;
> > 
> > Do you actually need to configure the trickle charger when there is
> > nothing to charge?
> 
> These are the options for the trickle chager:
> MAX31335_TRICKLE_REG_TRICKLE bits
> 
> 0x0: 3KΩ in series with a Schottky diode
> 0x1: 3KΩ in series with a Schottky diode
> 0x2: 6KΩ in series with a Schottky diode 
> 0x3: 11KΩ in series with a Schottky diode
> 0x4: 3KΩ in series with a diode+Schottky diode
> 0x5: 3KΩ in series with a diode+Schottky diode
> 0x6: 6KΩ in series with a diode+Schottky diode
> 0x7: 11KΩ in series with a diode+Schottky diode
> 

Then you need a property to select with diodes you are going to use. The
ABX80X supports something similar.

> > 
> > > +
> > > +	return regmap_write(max31335->regmap, MAX31335_TRICKLE_REG,
> > > +			    FIELD_PREP(MAX31335_TRICKLE_REG_TRICKLE, i) |
> > > +				       MAX31335_TRICKLE_REG_EN_TRICKLE);
> > > +}
> > > +
> > > +static int max31335_clkout_register(struct device *dev)
> > > +{
> > > +	struct max31335_data *max31335 = dev_get_drvdata(dev);
> > > +	int ret;
> > > +
> > > +	if (!device_property_present(dev, "#clock-cells"))
> > > +		return 0;
> > 
> > Is the clock output disabled by default?
> 
> No, I will disable it.

The CCF is responsible to disable the clock, else you will have a glitch
in the clock at boot time which will break use cases. But for this to
work, you will have to always register the clock.

> 
> > 
> > > +
> > > +static int max31335_probe(struct i2c_client *client)
> > > +{
> > > +	struct max31335_data *max31335;
> > > +	struct device *hwmon;
> > > +	int ret;
> > > +
> > > +	max31335 = devm_kzalloc(&client->dev, sizeof(*max31335),
> > GFP_KERNEL);
> > > +	if (!max31335)
> > > +		return -ENOMEM;
> > > +
> > > +	max31335->regmap = devm_regmap_init_i2c(client,
> > &regmap_config);
> > > +	if (IS_ERR(max31335->regmap))
> > > +		return PTR_ERR(max31335->regmap);
> > > +
> > > +	i2c_set_clientdata(client, max31335);
> > > +
> > > +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 1);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	ret = regmap_write(max31335->regmap, MAX31335_RTC_RESET, 0);
> > > +	if (ret)
> > > +		return ret;
> > 
> > What does this register do?
> > 
> 
> RTC Software Reset Register: 
> 0x0: Device is in normal mode.
> 0x1: Resets the digital block and the I2C programmable registers except for
> Timestamp/RAM registers and the SWRST bit. Oscillator is disabled.
> 
> The bit doesn't clear itself.
> 

Then you definitively don't want to do this, this will invalidate time
and date as the oscillator is disabled and this renders the RTC useless.
The whole point of the RTC is that it survives the reboot or shutdown of
the system.


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

Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Guenter Roeck]

On 11/2/23 09:57, Alexandre Belloni wrote:
[ ... ]
>>>> +static int max31335_read_offset(struct device *dev, long *offset)
>>>> +{
>>>> +	struct max31335_data *max31335 = dev_get_drvdata(dev);
>>>> +	u32 value;
>>>> +	int ret;
>>>> +
>>>> +	ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET,
>>> &value);
>>>> +	if (ret)
>>>> +		return ret;
>>>> +
>>>> +	*offset = value;
>>>
>>> This is super dubious, what is the unit of MAX31335_AGING_OFFSET ?
>>>
>>
>> There is not additional information on the AGING_OFFSET register (no
>> other offset registers).
>> I treated it as a raw value that user can write/read. Should I drop the
>> offset implementation?
>>
> 
> The value exposed to userspace is in parts per billion. If you can't do
> the conversion, then you have to drop it.
> 

The max31334 datasheet says "Resolution = 0.477ppm". Again, the datasheet for
max31335 is not public, so it is impossible to say what the resolution is
for that chip, but I would assume that it is documented.

Guenter

Re: [PATCH v4 1/2] dt-bindings: rtc: max31335: add max31335 bindings

[Krzysztof Kozlowski]

On 01/11/2023 10:48, Antoniu Miclaus wrote:
> Document the Analog Devices MAX31335 device tree bindings.
> 

...

>;
> +        #size-cells = <0>;
> +
> +        rtc@68 {
> +            compatible = "adi,max31335";
> +            reg = <0x68>;
> +            pinctrl-0 = <&rtc_nint_pins>;
> +            interrupts-extended = <&gpio1 16 IRQ_TYPE_LEVEL_HIGH>;
> +            trickle-resistor-ohms = <6000>;
> +            aux-voltage-chargeable =<1>;

Missing space after '='.

Keep Reviewed-by tag.

Best regards,
Krzysztof