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Message-ID: <96d7bf00-a5f8-486f-912d-931e918f3fa3@roeck-us.net>
Date: Tue, 31 Oct 2023 11:09:35 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>, patrick@...cx.xyz,
Jean Delvare <jdelvare@...e.com>,
Jonathan Corbet <corbet@....net>
Cc: Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, linux-i2c@...r.kernel.org,
linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 2/2] hwmon: pmbus: Add ltc4286 driver
On 10/31/23 00:21, Delphine CC Chiu wrote:
> Add a driver to support ltc4286 chip
>
> Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>
>
> Changelog:
> v3 - Use dev_err_probe() instead of dev_err()
> - The VRANGE_SELECT bit only be written if it actually changed
> - Avoid the info pointer being overwritten
> - Check the MBR value range to avoid overflow
> - Revise ltc4286.rst to corrcet description
> v2 - Revise Linear Technologies LTC4286 to
> Analog Devices LTC4286 in Kconfig
> - Add more description for this driver in Kconfig
> - Add some comments for MBR setting in ltc4286.c
> - Add ltc4286.rst
> ---
> Documentation/hwmon/ltc4286.rst | 95 +++++++++++++++++
Needs to be added to Documentation/hwmon/index.rst
> drivers/hwmon/pmbus/Kconfig | 9 ++
> drivers/hwmon/pmbus/Makefile | 1 +
> drivers/hwmon/pmbus/ltc4286.c | 178 ++++++++++++++++++++++++++++++++
> 4 files changed, 283 insertions(+)
> create mode 100644 Documentation/hwmon/ltc4286.rst
> create mode 100644 drivers/hwmon/pmbus/ltc4286.c
>
> diff --git a/Documentation/hwmon/ltc4286.rst b/Documentation/hwmon/ltc4286.rst
> new file mode 100644
> index 000000000000..2cd149676d86
> --- /dev/null
> +++ b/Documentation/hwmon/ltc4286.rst
> @@ -0,0 +1,95 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver ltc4286
> +=====================
> +
> +Supported chips:
> +
> + * Analog Devices LTC4286
> +
> + Prefix: 'ltc4286'
> +
> + Addresses scanned: -
> +
> + Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ltc4286.pdf
> +
> + * Analog Devices LTC4287
> +
> + Prefix: 'ltc4287'
> +
> + Addresses scanned: -
> +
> + Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ltc4287.pdf
> +
> +Author: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>
> +
> +
> +Description
> +-----------
> +
> +This driver supports hardware monitoring for Analog Devices LTC4286
> +and LTC4287 Hot-Swap Controller and Digital Power Monitors.
> +
> +LTC4286 and LTC4287 are hot-swap controllers that allow a circuit board
> +to be removed from or inserted into a live backplane. They also feature
> +current and voltage readback via an integrated 12 bit analog-to-digital
> +converter (ADC), accessed using a PMBus interface.
> +
> +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.
> +
> +The shunt value in micro-ohms can be set via device tree at compile-time. Please
> +refer to the Documentation/devicetree/bindings/hwmon/lltc,ltc4286.yaml for bindings
> +if the device tree is used.
> +
> +
> +Platform data support
> +---------------------
> +
> +The driver supports standard PMBus driver platform data. Please see
> +Documentation/hwmon/pmbus.rst for details.
> +
> +
> +Sysfs entries
> +-------------
> +
> +The following attributes are supported. Limits are read-write, history reset
> +attributes are write-only, all other attributes are read-only.
> +
> +======================= =======================================================
> +in1_label "vin"
> +in1_input Measured voltage.
> +in1_alarm Input voltage alarm.
> +in1_min Minimum input voltage.
> +in1_max Maximum input voltage.
> +
> +in2_label "vout1"
> +in2_input Measured voltage.
> +in2_alarm Output voltage alarm.
> +in2_min Minimum output voltage.
> +in2_max Maximum output voltage.
> +
> +curr1_label "iout1"
> +curr1_input Measured current.
> +curr1_alarm Output current alarm.
> +curr1_max Maximum current.
> +
> +power1_label "pin"
> +power1_input Input power.
> +power1_alarm Input power alarm.
> +power1_max Maximum poewr.
> +
> +temp1_input Chip temperature.
> +temp1_min Minimum chip temperature.
> +temp1_max Maximum chip temperature.
> +temp1_crit Critical chip temperature.
> +temp1_alarm Chip temperature alarm.
> +======================= =======================================================
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index b4e93bd5835e..f2b53e8abc3c 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -226,6 +226,15 @@ config SENSORS_LTC3815
>
> This driver can also be built as a module. If so, the module will
> be called ltc3815.
Add empty line
> +config SENSORS_LTC4286
> + bool "Analog Devices LTC4286"
> + help
> + LTC4286 is an integrated solution for hot swap applications that
> + allows a board to be safely inserted and removed from a live
> + backplane.
> + This chip could be used to monitor voltage, current, ...etc.
> + If you say yes here you get hardware monitoring support for Analog
> + Devices LTC4286.
>
> config SENSORS_MAX15301
> tristate "Maxim MAX15301"
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 84ee960a6c2d..94e28f6d6a61 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -24,6 +24,7 @@ obj-$(CONFIG_SENSORS_LM25066) += lm25066.o
> obj-$(CONFIG_SENSORS_LT7182S) += lt7182s.o
> obj-$(CONFIG_SENSORS_LTC2978) += ltc2978.o
> obj-$(CONFIG_SENSORS_LTC3815) += ltc3815.o
> +obj-$(CONFIG_SENSORS_LTC4286) += ltc4286.o
> obj-$(CONFIG_SENSORS_MAX15301) += max15301.o
> obj-$(CONFIG_SENSORS_MAX16064) += max16064.o
> obj-$(CONFIG_SENSORS_MAX16601) += max16601.o
> diff --git a/drivers/hwmon/pmbus/ltc4286.c b/drivers/hwmon/pmbus/ltc4286.c
> new file mode 100644
> index 000000000000..042d3af99489
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/ltc4286.c
> @@ -0,0 +1,178 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/pmbus.h>
> +#include "pmbus.h"
> +
> +/* LTC4286 register */
> +#define LTC4286_MFR_CONFIG1 0xF2
> +
> +/* LTC4286 configuration */
> +#define VRANGE_SELECT_BIT BIT(1)
> +
> +#define LTC4286_MFR_ID_SIZE 3
> +#define VRANGE_25P6 0
> +
> +enum chips { ltc4286, ltc4287 };
Not really used anywhere and can be dropped.
> +
> +/*
> + * Initialize the MBR as default settings which is referred to LTC4286 datasheet
> + * (March 22, 2022 version) table 3 page 16
> + */
> +static struct pmbus_driver_info ltc4286_info = {
> + .pages = 1,
> + .format[PSC_VOLTAGE_IN] = direct,
> + .format[PSC_VOLTAGE_OUT] = direct,
> + .format[PSC_CURRENT_OUT] = direct,
> + .format[PSC_POWER] = direct,
> + .format[PSC_TEMPERATURE] = direct,
> + .m[PSC_VOLTAGE_IN] = 32,
> + .b[PSC_VOLTAGE_IN] = 0,
> + .R[PSC_VOLTAGE_IN] = 1,
> + .m[PSC_VOLTAGE_OUT] = 32,
> + .b[PSC_VOLTAGE_OUT] = 0,
> + .R[PSC_VOLTAGE_OUT] = 1,
> + .m[PSC_CURRENT_OUT] = 1024,
> + .b[PSC_CURRENT_OUT] = 0,
> + /*
> + * The rsense value used in MBR formula in LTC4286 datasheet should be ohm unit.
> + * However, the rsense value that user input is mirco ohm.
micro
> + * Thus, the MBR setting which involves rsense should be shifted by 6 digits.
> + */
> + .R[PSC_CURRENT_OUT] = 3 - 6,
> + .m[PSC_POWER] = 1,
> + .b[PSC_POWER] = 0,
> + /*
> + * The rsense value used in MBR formula in LTC4286 datasheet should be ohm unit.
> + * However, the rsense value that user input is mirco ohm.
micro
> + * Thus, the MBR setting which involves rsense should be shifted by 6 digits.
> + */
> + .R[PSC_POWER] = 4 - 6,
> + .m[PSC_TEMPERATURE] = 1,
> + .b[PSC_TEMPERATURE] = 273,
> + .R[PSC_TEMPERATURE] = 0,
> + .func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
> + PMBUS_HAVE_PIN | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_VOUT |
> + PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_TEMP,
> +};
> +
> +static const struct i2c_device_id ltc4286_id[] = { { "ltc4286", ltc4286 },
> + { "ltc4287", ltc4287 },
> + {} };
> +MODULE_DEVICE_TABLE(i2c, ltc4286_id);
> +
> +static int ltc4286_probe(struct i2c_client *client)
> +{
> + int ret;
> + const struct i2c_device_id *mid;
> + u8 block_buffer[I2C_SMBUS_BLOCK_MAX + 1];
> + struct pmbus_driver_info *info;
> + u32 rsense;
> +
> + ret = i2c_smbus_read_block_data(client, PMBUS_MFR_ID, block_buffer);
> + if (ret < 0) {
> + return dev_err_probe(&client->dev, ret,
> + "Failed to read manufacturer id\n");
> + }
> +
> + /*
> + * Refer to ltc4286 datasheet page 20
> + * the manufacturer id is LTC
> + */
> + if (ret != LTC4286_MFR_ID_SIZE ||
> + strncmp(block_buffer, "LTC", LTC4286_MFR_ID_SIZE)) {
> + return dev_err_probe(&client->dev, ret,
> + "Manufacturer id mismatch\n");
> + }
> +
> + ret = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, block_buffer);
> + if (ret < 0) {
> + return dev_err_probe(&client->dev, ret,
> + "Failed to read manufacturer model\n");
> + }
> +
> + for (mid = ltc4286_id; mid->name[0]; mid++) {
> + if (!strncasecmp(mid->name, block_buffer, strlen(mid->name)))
> + break;
> + }
> + if (!mid->name[0])
> + return dev_err_probe(&client->dev, -ENODEV,
> + "Unsupported device\n");
> +
> + ret = of_property_read_u32(client->dev.of_node,
> + "shunt-resistor-micro-ohms", &rsense);
> + if (ret < 0)
> + return ret;
> +
> + if (rsense == 0)
> + return -EINVAL;
> +
> + info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
> + if (!info)
> + return -ENOMEM;
> + memcpy(info, <c4286_info, sizeof(*info));
devm_kmemdup()
> +
> + /* Default of VRANGE_SELECT = 1, 102.4V */
> + if (device_property_read_bool(&client->dev, "adi,vrange-low-enable")) {
> + /* Setup MFR1 CONFIG register bit 1 VRANGE_SELECT */
> + ret = i2c_smbus_read_word_data(client, LTC4286_MFR_CONFIG1);
> + if (ret < 0) {
> + return dev_err_probe(
> + &client->dev, ret,
> + "Failed to read manufacturer configuration one\n");
> + }
> +
> + if ((ret & VRANGE_SELECT_BIT) != VRANGE_25P6) {
> + ret &= ~VRANGE_SELECT_BIT; /* VRANGE_SELECT = 0, 25.6V */
> + ret = i2c_smbus_write_word_data(
> + client, LTC4286_MFR_CONFIG1, ret);
> + if (ret < 0)
> + return dev_err_probe(&client->dev, ret,
> + "Failed to set vrange\n");
> + }
> +
> + info->m[PSC_VOLTAGE_IN] = 128;
> + info->m[PSC_VOLTAGE_OUT] = 128;
> + info->m[PSC_POWER] = 4 * rsense;
> + if (info->m[PSC_POWER] > INT_MAX)
This is too late. See below.
> + return dev_err_probe(&client->dev, -ERANGE,
> + "Power coefficient overflow\n");
> + } else {
> + info->m[PSC_POWER] = rsense;
> + if (info->m[PSC_POWER] > INT_MAX)
> + return dev_err_probe(&client->dev, -ERANGE,
> + "Power coefficient overflow\n");
This still needs to be written into the chip. There is no guarantee that
the chip is in its default configuration when the driver is loaded.
> + }
> +
> + info->m[PSC_CURRENT_OUT] = 1024 * rsense;
> + if (info->m[PSC_CURRENT_OUT] > INT_MAX)
This is too late. If rsense == INT_MAX, for example, 1024 * rsense
will be some negative number.
> + return dev_err_probe(&client->dev, -ERANGE,
> + "Current coefficient overflow\n");
> +
> + return pmbus_do_probe(client, info);
> +}
> +
> +static const struct of_device_id ltc4286_of_match[] = {
> + { .compatible = "lltc,ltc4286" },
> + { .compatible = "lltc,ltc4287" },
> + {}
> +};
> +
> +static struct i2c_driver ltc4286_driver = {
> + .driver = {
> + .name = "ltc4286",
> + .of_match_table = ltc4286_of_match,
> + },
> + .probe = ltc4286_probe,
> + .id_table = ltc4286_id,
> +};
> +
> +module_i2c_driver(ltc4286_driver);
> +
> +MODULE_AUTHOR("Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>");
> +MODULE_DESCRIPTION("PMBUS driver for LTC4286 and compatibles");
> +MODULE_LICENSE("GPL");
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