[PATCH 0/2] Add support for LT3074 low voltage linear regulator

[PATCH 0/2] Add support for LT3074 low voltage linear regulator

[Cedric Encarnacion]

Introduce hardware monitoring and regulator support for LT3074. The
component is an ultrafast, ultralow noise 3A, 5.5V dropout linear
regulator with a PMBus serial interface that allows telemetry for
input/output voltage, output current, and die temperature. It has a
single channel and requires a bias voltage which can be monitored via
manufacturer-specific registers.

Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
---
Cedric Encarnacion (2):
      dt-bindings: trivial-devices: add lt3074
      hwmon: (pmbus/lt3074): add support for lt3074

 .../devicetree/bindings/trivial-devices.yaml       |   2 +
 Documentation/hwmon/index.rst                      |   1 +
 Documentation/hwmon/lt3074.rst                     |  72 ++++++++++++
 drivers/hwmon/pmbus/Kconfig                        |  18 +++
 drivers/hwmon/pmbus/Makefile                       |   1 +
 drivers/hwmon/pmbus/lt3074.c                       | 122 +++++++++++++++++++++
 6 files changed, 216 insertions(+)
---
base-commit: a76539b293677c5c163b9285b0cd8dd420d33989
change-id: 20250124-upstream-lt3074-123384246e0b

Best regards,
-- 
Cedric Encarnacion <cedricjustine.encarnacion@analog.com>

[PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Cedric Encarnacion]

Add Analog Devices LT3074 Ultralow Noise, High PSRR Dropout Linear
Regulator.

Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
---
 Documentation/devicetree/bindings/trivial-devices.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml
index 6bdcd055e763..8f7a8e28fb97 100644
--- a/Documentation/devicetree/bindings/trivial-devices.yaml
+++ b/Documentation/devicetree/bindings/trivial-devices.yaml
@@ -41,6 +41,8 @@ properties:
           - adi,ad5110
             # Analog Devices ADP5589 Keypad Decoder and I/O Expansion
           - adi,adp5589
+            # Analog Devices LT3074 3A, 5.5V Low Voltage Linear Regulator
+          - adi,lt3074
             # Analog Devices LT7182S Dual Channel 6A, 20V PolyPhase Step-Down Silent Switcher
           - adi,lt7182s
             # AMS iAQ-Core VOC Sensor

-- 
2.39.5

[PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[Cedric Encarnacion]

Add hardware monitoring and regulator support for LT3074. The LT3074 is an
ultrafast, ultralow noise 3A, 5.5V dropout linear regulator. The PMBus
serial interface allows telemetry for input/output voltage, bias voltage,
output current, and die temperature.

Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
---
 Documentation/hwmon/index.rst  |   1 +
 Documentation/hwmon/lt3074.rst |  72 ++++++++++++++++++++++++
 drivers/hwmon/pmbus/Kconfig    |  18 ++++++
 drivers/hwmon/pmbus/Makefile   |   1 +
 drivers/hwmon/pmbus/lt3074.c   | 122 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 214 insertions(+)

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index b1ea445479b0..5be511506d50 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -122,6 +122,7 @@ Hardware Monitoring Kernel Drivers
    lm95234
    lm95245
    lochnagar
+   lt3074
    lt7182s
    ltc2992
    ltc2945
diff --git a/Documentation/hwmon/lt3074.rst b/Documentation/hwmon/lt3074.rst
new file mode 100644
index 000000000000..234f369153cf
--- /dev/null
+++ b/Documentation/hwmon/lt3074.rst
@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver lt3074
+====================
+
+Supported chips:
+
+  * Analog Devices LT3074
+
+    Prefix: 'lt3074'
+
+    Addresses scanned: -
+
+    Datasheet: https://www.analog.com/en/products/lt3074.html
+
+Authors: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
+
+
+Description
+-----------
+
+This driver supports hardware monitoring for Analog Devices LT3074 Linear
+Regulator with PMBus interface.
+
+The LT3074 is a low voltage, ultra-low noise and ultra-fast transient
+response linear regulator with PMBus serial interface. PMBus telemetry
+feature provides information regarding the output voltage and current,
+input voltage, bias voltage and die temperature.
+
+The driver is a client driver to the core PMBus driver. Please see
+Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate
+the devices explicitly. Please see Documentation/i2c/instantiating-devices.rst
+for details.
+
+Platform data support
+---------------------
+
+The driver supports standard PMBus driver platform data.
+
+Sysfs entries
+-------------
+
+======================= =======================================================
+in1_label		"vin"
+in1_input		Measured input voltage
+in1_max			Input overvoltage warning limit
+in1_max_alarm		Input overvoltage warning status
+in1_min			Input undervoltage warning limit
+in1_min_alarm		Input undervoltage warning status
+in2_label		"vmon"
+in2_input		Measured bias voltage
+in2_max			Bias overvoltage warning limit
+in2_min			Bias undervoltage warning limit
+in3_label		"vout1"
+in3_input		Measured output voltage
+in3_max			Output overvoltage warning limit
+in3_max_alarm		Output overvoltage warning status
+in3_min			Output undervoltage warning limit
+in3_min_alarm		Output undervoltage warning status
+curr1_label		"iout1"
+curr1_input		Measured output current.
+curr1_crit		Output overcurrent fault limit
+curr1_crit_alarm	Output overcurrent fault status
+temp1_input		Measured temperature
+temp1_max		Maximum temperature limit
+temp1_max_alarm		Overtemperature warning status
+======================= =======================================================
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 419469f40ba0..32564a64e225 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -209,6 +209,24 @@ config SENSORS_LM25066_REGULATOR
 	  If you say yes here you get regulator support for National
 	  Semiconductor LM25066, LM5064, and LM5066.
 
+config SENSORS_LT3074
+	tristate "Analog Devices LT3074"
+	help
+	  If you say yes here you get hardware monitoring support for Analog
+	  Devices LT3074.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called lt3074.
+
+config SENSORS_LT3074_REGULATOR
+	tristate "Regulator support for LT3074"
+	depends on SENSORS_LT3074 && REGULATOR
+	help
+	  If you say yes here you get regulator support for Analog Devices
+	  LT3074. The LT3074 is a low voltage, ultralow noise, high PSRR,
+	  dropout linear regulator. The device supplies up to 3A with a
+	  typical dropout voltage of 45mV.
+
 config SENSORS_LT7182S
 	tristate "Analog Devices LT7182S"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index c7eb7739b7f8..5ef388c10581 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_SENSORS_IR38064)	+= ir38064.o
 obj-$(CONFIG_SENSORS_IRPS5401)	+= irps5401.o
 obj-$(CONFIG_SENSORS_ISL68137)	+= isl68137.o
 obj-$(CONFIG_SENSORS_LM25066)	+= lm25066.o
+obj-$(CONFIG_SENSORS_LT3074)	+= lt3074.o
 obj-$(CONFIG_SENSORS_LT7182S)	+= lt7182s.o
 obj-$(CONFIG_SENSORS_LTC2978)	+= ltc2978.o
 obj-$(CONFIG_SENSORS_LTC3815)	+= ltc3815.o
diff --git a/drivers/hwmon/pmbus/lt3074.c b/drivers/hwmon/pmbus/lt3074.c
new file mode 100644
index 000000000000..430e3a0c0a5f
--- /dev/null
+++ b/drivers/hwmon/pmbus/lt3074.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hardware monitoring driver for Analog Devices LT3074
+ *
+ * Copyright (C) 2025 Analog Devices, Inc.
+ */
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+
+#include "pmbus.h"
+
+#define LT3074_MFR_READ_VBIAS			0xc6
+#define LT3074_MFR_BIAS_OV_WARN_LIMIT		0xc7
+#define LT3074_MFR_BIAS_UV_WARN_LIMIT		0xc8
+#define LT3074_MFR_SPECIAL_ID			0xe7
+
+#define LT3074_SPECIAL_ID_VALUE			0x1c1d
+
+static const struct regulator_desc __maybe_unused lt3074_reg_desc[] = {
+	PMBUS_REGULATOR_ONE("vout"),
+};
+
+static int lt3074_read_word_data(struct i2c_client *client, int page,
+				 int phase, int reg)
+{
+	switch (reg) {
+	case PMBUS_VIRT_READ_VMON:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_READ_VBIAS);
+	case PMBUS_VIRT_VMON_UV_WARN_LIMIT:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_BIAS_UV_WARN_LIMIT);
+	case PMBUS_VIRT_VMON_OV_WARN_LIMIT:
+		return pmbus_read_word_data(client, page, phase,
+					   LT3074_MFR_BIAS_OV_WARN_LIMIT);
+	default:
+		return -ENODATA;
+	}
+}
+
+static int lt3074_write_word_data(struct i2c_client *client, int page,
+				  int reg, u16 word)
+{
+	switch (reg) {
+	case PMBUS_VIRT_VMON_UV_WARN_LIMIT:
+		return pmbus_write_word_data(client, 0,
+					    LT3074_MFR_BIAS_UV_WARN_LIMIT,
+					    word);
+	case PMBUS_VIRT_VMON_OV_WARN_LIMIT:
+		return pmbus_write_word_data(client, 0,
+					    LT3074_MFR_BIAS_OV_WARN_LIMIT,
+					    word);
+	default:
+		return -ENODATA;
+	}
+}
+
+static struct pmbus_driver_info lt3074_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_TEMPERATURE] = linear,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
+		   PMBUS_HAVE_TEMP | PMBUS_HAVE_VMON |
+		   PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_STATUS_IOUT |
+		   PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
+	.read_word_data = lt3074_read_word_data,
+	.write_word_data = lt3074_write_word_data,
+#if IS_ENABLED(CONFIG_SENSORS_LT3074_REGULATOR)
+	.num_regulators = 1,
+	.reg_desc = lt3074_reg_desc,
+#endif
+};
+
+static int lt3074_probe(struct i2c_client *client)
+{
+	int ret;
+	struct device *dev = &client->dev;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENODEV;
+
+	ret = i2c_smbus_read_word_data(client, LT3074_MFR_SPECIAL_ID);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read ID\n");
+
+	if (ret != LT3074_SPECIAL_ID_VALUE)
+		return dev_err_probe(dev, -ENODEV, "ID mismatch\n");
+
+	return pmbus_do_probe(client, &lt3074_info);
+}
+
+static const struct i2c_device_id lt3074_id[] = {
+	{ "lt3074", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, lt3074_id);
+
+static const struct of_device_id lt3074_of_match[] = {
+	{ .compatible = "adi,lt3074" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, lt3074_of_match);
+
+static struct i2c_driver lt3074_driver = {
+	.driver = {
+		.name = "lt3074",
+		.of_match_table = of_match_ptr(lt3074_of_match),
+	},
+	.probe = lt3074_probe,
+	.id_table = lt3074_id,
+};
+module_i2c_driver(lt3074_driver);
+
+MODULE_AUTHOR("Cedric Encarnacion <cedricjustine.encarnacion@analog.com>");
+MODULE_DESCRIPTION("PMBus driver for Analog Devices LT3074");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");

-- 
2.39.5

Re: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[kernel test robot]

Hi Cedric,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a76539b293677c5c163b9285b0cd8dd420d33989]

url:    https://github.com/intel-lab-lkp/linux/commits/Cedric-Encarnacion/dt-bindings-trivial-devices-add-lt3074/20250124-234209
base:   a76539b293677c5c163b9285b0cd8dd420d33989
patch link:    https://lore.kernel.org/r/20250124-upstream-lt3074-v1-2-7603f346433e%40analog.com
patch subject: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074
config: hexagon-randconfig-r073-20250126 (https://download.01.org/0day-ci/archive/20250126/202501260605.Ad7sJxQM-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 19306351a2c45e266fa11b41eb1362b20b6ca56d)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250126/202501260605.Ad7sJxQM-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202501260605.Ad7sJxQM-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/hwmon/pmbus/lt3074.c:8:
   In file included from include/linux/i2c.h:19:
   In file included from include/linux/regulator/consumer.h:35:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:21:
   In file included from include/linux/mm.h:2223:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> drivers/hwmon/pmbus/lt3074.c:103:34: warning: unused variable 'lt3074_of_match' [-Wunused-const-variable]
     103 | static const struct of_device_id lt3074_of_match[] = {
         |                                  ^~~~~~~~~~~~~~~
   2 warnings generated.


vim +/lt3074_of_match +103 drivers/hwmon/pmbus/lt3074.c

   102	
 > 103	static const struct of_device_id lt3074_of_match[] = {
   104		{ .compatible = "adi,lt3074" },
   105		{}
   106	};
   107	MODULE_DEVICE_TABLE(of, lt3074_of_match);
   108	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[Guenter Roeck]

On 1/24/25 07:39, Cedric Encarnacion wrote:
> Add hardware monitoring and regulator support for LT3074. The LT3074 is an
> ultrafast, ultralow noise 3A, 5.5V dropout linear regulator. The PMBus
> serial interface allows telemetry for input/output voltage, bias voltage,
> output current, and die temperature.
> 
> Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
> ---
....
> +
> +static const struct i2c_device_id lt3074_id[] = {
> +	{ "lt3074", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, lt3074_id);
> +
> +static const struct of_device_id lt3074_of_match[] = {

Needs __maybe_unused

Guenter

Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Krzysztof Kozlowski]

On Fri, Jan 24, 2025 at 11:39:06PM +0800, Cedric Encarnacion wrote:
> Add Analog Devices LT3074 Ultralow Noise, High PSRR Dropout Linear
> Regulator.

Regulator? Then why is it trivial? No enable-gpios? No I2C interface?

Best regards,
Krzysztof

Re: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[kernel test robot]

Hi Cedric,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a76539b293677c5c163b9285b0cd8dd420d33989]

url:    https://github.com/intel-lab-lkp/linux/commits/Cedric-Encarnacion/dt-bindings-trivial-devices-add-lt3074/20250124-234209
base:   a76539b293677c5c163b9285b0cd8dd420d33989
patch link:    https://lore.kernel.org/r/20250124-upstream-lt3074-v1-2-7603f346433e%40analog.com
patch subject: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074
config: x86_64-randconfig-r071-20250126 (https://download.01.org/0day-ci/archive/20250128/202501280459.uH0yw7av-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250128/202501280459.uH0yw7av-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202501280459.uH0yw7av-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/hwmon/pmbus/lt3074.c:103:34: warning: 'lt3074_of_match' defined but not used [-Wunused-const-variable=]
     103 | static const struct of_device_id lt3074_of_match[] = {
         |                                  ^~~~~~~~~~~~~~~


vim +/lt3074_of_match +103 drivers/hwmon/pmbus/lt3074.c

   102	
 > 103	static const struct of_device_id lt3074_of_match[] = {
   104		{ .compatible = "adi,lt3074" },
   105		{}
   106	};
   107	MODULE_DEVICE_TABLE(of, lt3074_of_match);
   108	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[Guenter Roeck]

On Fri, Jan 24, 2025 at 11:39:07PM +0800, Cedric Encarnacion wrote:
> Add hardware monitoring and regulator support for LT3074. The LT3074 is an
> ultrafast, ultralow noise 3A, 5.5V dropout linear regulator. The PMBus
> serial interface allows telemetry for input/output voltage, bias voltage,
> output current, and die temperature.
> 
> Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>

Just in case it is not obvious: I do not apply or for the most part not
even review patches if the kernel test robot reported a problem.
This applies to all patches, not just this one.

Thanks,
Guenter

RE: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Encarnacion, Cedric justine]

> -----Original Message-----
> From: Krzysztof Kozlowski <krzk@kernel.org>
> Sent: Monday, January 27, 2025 3:52 PM
> To: Encarnacion, Cedric justine <Cedricjustine.Encarnacion@analog.com>
> Cc: Rob Herring <robh@kernel.org>; Krzysztof Kozlowski <krzk+dt@kernel.org>;
> Conor Dooley <conor+dt@kernel.org>; Jean Delvare <jdelvare@suse.com>;
> Guenter Roeck <linux@roeck-us.net>; Jonathan Corbet <corbet@lwn.net>;
> Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> hwmon@vger.kernel.org; linux-doc@vger.kernel.org; linux-i2c@vger.kernel.org
> Subject: Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074
> 
> [External]
> 
> On Fri, Jan 24, 2025 at 11:39:06PM +0800, Cedric Encarnacion wrote:
> > Add Analog Devices LT3074 Ultralow Noise, High PSRR Dropout Linear
> > Regulator.
> 
> Regulator? Then why is it trivial? No enable-gpios? No I2C interface?
> 
> Best regards,
> Krzysztof

I based this driver primarily on the LT7182S dual-channel silent switcher
regulator. The LT3074 is a single-channel device with basic enable and
power-good GPIOs, fewer registers, and fewer functionalities than the
LT7182S. Like other PMBus drivers, its GPIOs are not exposed.

Here are other PMBus regulators/power modules found in trivial-devices
I also used as reference:

- infineon,irps5401
- delta,q54sj108a2

Best regards,
Cedric

RE: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074

[Encarnacion, Cedric justine]

> -----Original Message-----
> From: Guenter Roeck <groeck7@gmail.com> On Behalf Of Guenter Roeck
> Sent: Thursday, January 30, 2025 12:15 AM
> To: Encarnacion, Cedric justine <Cedricjustine.Encarnacion@analog.com>
> Cc: Rob Herring <robh@kernel.org>; Krzysztof Kozlowski <krzk+dt@kernel.org>;
> Conor Dooley <conor+dt@kernel.org>; Jean Delvare <jdelvare@suse.com>;
> Jonathan Corbet <corbet@lwn.net>; Delphine CC Chiu
> <Delphine_CC_Chiu@wiwynn.com>; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-hwmon@vger.kernel.org; linux-
> doc@vger.kernel.org; linux-i2c@vger.kernel.org
> Subject: Re: [PATCH 2/2] hwmon: (pmbus/lt3074): add support for lt3074
> 
> [External]
> 
> On Fri, Jan 24, 2025 at 11:39:07PM +0800, Cedric Encarnacion wrote:
> > Add hardware monitoring and regulator support for LT3074. The LT3074 is an
> > ultrafast, ultralow noise 3A, 5.5V dropout linear regulator. The PMBus
> > serial interface allows telemetry for input/output voltage, bias voltage,
> > output current, and die temperature.
> >
> > Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@analog.com>
> 
> Just in case it is not obvious: I do not apply or for the most part not
> even review patches if the kernel test robot reported a problem.
> This applies to all patches, not just this one.
> 
> Thanks,
> Guenter

This is understood. I'll submit a new patch version soon to address the kernel
test robot warning.

Best regards,
Cedric

Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Krzysztof Kozlowski]

On 06/02/2025 10:05, Encarnacion, Cedric justine wrote:
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzk@kernel.org>
>> Sent: Monday, January 27, 2025 3:52 PM
>> To: Encarnacion, Cedric justine <Cedricjustine.Encarnacion@analog.com>
>> Cc: Rob Herring <robh@kernel.org>; Krzysztof Kozlowski <krzk+dt@kernel.org>;
>> Conor Dooley <conor+dt@kernel.org>; Jean Delvare <jdelvare@suse.com>;
>> Guenter Roeck <linux@roeck-us.net>; Jonathan Corbet <corbet@lwn.net>;
>> Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>;
>> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
>> hwmon@vger.kernel.org; linux-doc@vger.kernel.org; linux-i2c@vger.kernel.org
>> Subject: Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074
>>
>> [External]
>>
>> On Fri, Jan 24, 2025 at 11:39:06PM +0800, Cedric Encarnacion wrote:
>>> Add Analog Devices LT3074 Ultralow Noise, High PSRR Dropout Linear
>>> Regulator.
>>
>> Regulator? Then why is it trivial? No enable-gpios? No I2C interface?
>>
>> Best regards,
>> Krzysztof
> 
> I based this driver primarily on the LT7182S dual-channel silent switcher
> regulator. 


I do not understand why the base of driver matters here? If it was based
on LTFOOBARGROUNDHOG1 would it change something? I know neither LT7182S
nor the LTFOOBARGROUNDHOG1. And driver matters here even less - bindings
are about hardware, not given implementation in OS.

> The LT3074 is a single-channel device with basic enable and
> power-good GPIOs, fewer registers, and fewer functionalities than the

So it has GPIOs? And by GPIOs you mean what the SoC/CPU, thus the
operating system, sees as GPIOs or something else?

> LT7182S. Like other PMBus drivers, its GPIOs are not exposed.
> 
> Here are other PMBus regulators/power modules found in trivial-devices
> I also used as reference:
> 
> - infineon,irps5401
> - delta,q54sj108a2


I don't know these devices so still no clue. Please rather explain in
the terms of the hardware, e.g. what this device has or has not. See
also regulator bindings.

Best regards,
Krzysztof

RE: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Encarnacion, Cedric justine]

> On 06/02/2025 10:05, Encarnacion, Cedric justine wrote:
> >> -----Original Message-----
> >> From: Krzysztof Kozlowski <krzk@kernel.org>
> >> Sent: Monday, January 27, 2025 3:52 PM
> >> To: Encarnacion, Cedric justine <Cedricjustine.Encarnacion@analog.com>
> >> Cc: Rob Herring <robh@kernel.org>; Krzysztof Kozlowski
> <krzk+dt@kernel.org>;
> >> Conor Dooley <conor+dt@kernel.org>; Jean Delvare
> <jdelvare@suse.com>;
> >> Guenter Roeck <linux@roeck-us.net>; Jonathan Corbet <corbet@lwn.net>;
> >> Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>;
> >> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> >> hwmon@vger.kernel.org; linux-doc@vger.kernel.org; linux-
> i2c@vger.kernel.org
> >> Subject: Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074
> >>
> >> [External]
> >>
> >> On Fri, Jan 24, 2025 at 11:39:06PM +0800, Cedric Encarnacion wrote:
> >>> Add Analog Devices LT3074 Ultralow Noise, High PSRR Dropout Linear
> >>> Regulator.
> >>
> >> Regulator? Then why is it trivial? No enable-gpios? No I2C interface?
> >>
> >> Best regards,
> >> Krzysztof
> >
> > I based this driver primarily on the LT7182S dual-channel silent switcher
> > regulator.
> 
> 
> I do not understand why the base of driver matters here? If it was based
> on LTFOOBARGROUNDHOG1 would it change something? I know neither
> LT7182S
> nor the LTFOOBARGROUNDHOG1. And driver matters here even less -
> bindings
> are about hardware, not given implementation in OS.
> 
> > The LT3074 is a single-channel device with basic enable and
> > power-good GPIOs, fewer registers, and fewer functionalities than the
> 
> So it has GPIOs? And by GPIOs you mean what the SoC/CPU, thus the
> operating system, sees as GPIOs or something else?

Yes, the OS sees these as GPIOs.

> 
> > LT7182S. Like other PMBus drivers, its GPIOs are not exposed.
> >
> > Here are other PMBus regulators/power modules found in trivial-devices
> > I also used as reference:
> >
> > - infineon,irps5401
> > - delta,q54sj108a2
> 
> 
> I don't know these devices so still no clue. Please rather explain in
> the terms of the hardware, e.g. what this device has or has not. See
> also regulator bindings.

The device has enable-gpio and status-gpio. It also has registers of
similar functionality which the core driver accesses instead for
toggling enable and monitoring status of the device.

Upon checking regulator bindings and other related bindings for
PMBus devices with regulator support, this indeed should be a
separate binding outside of trivial devices. Please let me know
what do you suggest.

Best Regards,
Cedric

Re: [PATCH 1/2] dt-bindings: trivial-devices: add lt3074

[Krzysztof Kozlowski]

On 17/02/2025 10:30, Encarnacion, Cedric justine wrote:
>>
>>> LT7182S. Like other PMBus drivers, its GPIOs are not exposed.
>>>
>>> Here are other PMBus regulators/power modules found in trivial-devices
>>> I also used as reference:
>>>
>>> - infineon,irps5401
>>> - delta,q54sj108a2
>>
>>
>> I don't know these devices so still no clue. Please rather explain in
>> the terms of the hardware, e.g. what this device has or has not. See
>> also regulator bindings.
> 
> The device has enable-gpio and status-gpio. It also has registers of
> similar functionality which the core driver accesses instead for
> toggling enable and monitoring status of the device.
> 
> Upon checking regulator bindings and other related bindings for
> PMBus devices with regulator support, this indeed should be a
> separate binding outside of trivial devices. Please let me know
> what do you suggest.

Even the GPIOs are outside of trivial devices, so for that sole reason
this should not be here but in its own binding.

Best regards,
Krzysztof