Re: [PATCH hwmon-next v2 2/3] hwmon: (pmbus) Add support for MPS Multi-phase mp2888 controller

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Apr 19, 2021 at 04:02:20PM +0300, Vadim Pasternak wrote:
> Add support for mp2888 device from Monolithic Power Systems, Inc. (MPS)
> vendor. This is a digital, multi-phase, pulse-width modulation
> controller.
> 
> This device supports:
> - One power rail.
> - Programmable Multi-Phase up to 10 Phases.
> - PWM-VID Interface
> - One pages 0 for telemetry.
> - Programmable pins for PMBus Address.
> - Built-In EEPROM to Store Custom Configurations.
> - Can configured VOUT readout in direct or VID format and allows
>   setting of different formats on rails 1 and 2. For VID the following
>   protocols are available: VR13 mode with 5-mV DAC; VR13 mode with
>   10-mV DAC, IMVP9 mode with 5-mV DAC.
> 
> Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
> ---
> v1->v2:
>  Comments pointed out by Guenter:
>   - Use standard access for getting PMBUS_OT_WARN_LIMIT,
>     PMBUS_VIN_OV_FAULT_LIMIT, PMBUS_VIN_UV_WARN_LIMIT.
>   - Use linear11 conversion for PMBUS_READ_VIN, PMBUS_READ_POUT,
>     PMBUS_READ_PIN, PMBUS_READ_TEMPERATURE_1 and adjust coefficients.
>   - Add reading phases current from the dedicated registers.
>   - Add comment for not implemented or implemented not according to the
> 	spec registers, for which "ENXIO" code is returned.
>   - Set PMBUS_HAVE_IOUT" statically.
>   Notes from Vadim:
>   - READ_IOUT uses direct format, so I did not adjust it like the below
>     registers.
> ---
>  Documentation/hwmon/mp2888.rst | 111 ++++++++++++
>  drivers/hwmon/pmbus/Kconfig    |   9 +
>  drivers/hwmon/pmbus/Makefile   |   1 +
>  drivers/hwmon/pmbus/mp2888.c   | 373 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 494 insertions(+)
>  create mode 100644 Documentation/hwmon/mp2888.rst
>  create mode 100644 drivers/hwmon/pmbus/mp2888.c
> 
> diff --git a/Documentation/hwmon/mp2888.rst b/Documentation/hwmon/mp2888.rst
> new file mode 100644
> index 000000000000..7839a010642a
> --- /dev/null
> +++ b/Documentation/hwmon/mp2888.rst
> @@ -0,0 +1,111 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp2888
> +====================
> +
> +Supported chips:
> +
> +  * MPS MP12254
> +
> +    Prefix: 'mp2888'
> +
> +Author:
> +
> +	Vadim Pasternak <vadimp@nvidia.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +vendor dual-loop, digital, multi-phase controller MP2888.
> +
> +This device: supports:
> +
> +- One power rail.
> +- Programmable Multi-Phase up to 10 Phases.
> +- PWM-VID Interface
> +- One pages 0 for telemetry.
> +- Programmable pins for PMBus Address.
> +- Built-In EEPROM to Store Custom Configurations.
> +
> +Device complaint with:
> +
> +- PMBus rev 1.3 interface.
> +
> +Device supports direct format for reading output current, output voltage,
> +input and output power and temperature.
> +Device supports linear format for reading input voltage and input power.
> +
> +The driver provides the next attributes for the current:
> +
> +- for current out input and maximum alarm;
> +- for phase current: input and label.
> +
> +The driver exports the following attributes via the 'sysfs' files, where:
> +
> +- 'n' is number of configured phases (from 1 to 10);
> +- index 1 for "iout";
> +- indexes 2 ... 1 + n for phases.
> +
> +**curr1_alarm**
> +
> +**curr[1-{1+n}]_input**
> +
> +**curr[1-{1+n}]_label**
> +
> +The driver provides the next attributes for the voltage:
> +
> +- for voltage in: input, low and high critical thresholds, low and high
> +  critical alarms;
> +- for voltage out: input and high alarm;
> +
> +The driver exports the following attributes via the 'sysfs' files, where
> +
> +**in1_crit**
> +
> +**in1_crit_alarm**
> +
> +**in1_input**
> +
> +**in1_label**
> +
> +**in1_min**
> +
> +**in1_min_alarm**
> +
> +**in2_alarm**
> +
> +**in2_input**
> +
> +**in2_label**
> +
> +The driver provides the next attributes for the power:
> +
> +- for power in alarm and input.
> +- for power out: cap, cap alarm an input.
> +
> +The driver exports the following attributes via the 'sysfs' files, where
> +- indexes 1 for "pin";
> +- indexes 2 for "pout";
> +
> +**power1_alarm**
> +
> +**power1_input**
> +
> +**power1_label**
> +
> +**power2_cap**
> +
> +**power2_cap_alarm**
> +
> +**power2_input**
> +
> +**power2_label**
> +
> +The driver provides the next attributes for the temperature:
> +
> +**temp1_input**
> +
> +**temp1_max**
> +
> +**temp1_max_alarm**
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 32d2fc850621..a57571928b31 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -211,6 +211,15 @@ config SENSORS_MAX8688
>  	  This driver can also be built as a module. If so, the module will
>  	  be called max8688.
>  
> +config SENSORS_MP2888
> +	tristate "MPS MP2888"
> +	help
> +	  If you say yes here you get hardware monitoring support for MPS
> +	  MP2888 Digital, Multi-Phase, Pulse-Width Modulation Controller.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called mp2888.
> +
>  config SENSORS_MP2975
>  	tristate "MPS MP2975"
>  	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 6a4ba0fdc1db..a6d7352621ca 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -24,6 +24,7 @@ obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
>  obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
>  obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
>  obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
> +obj-$(CONFIG_SENSORS_MP2888)	+= mp2888.o
>  obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
>  obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
>  obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
> diff --git a/drivers/hwmon/pmbus/mp2888.c b/drivers/hwmon/pmbus/mp2888.c
> new file mode 100644
> index 000000000000..5abe945a7bf9
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp2888.c
> @@ -0,0 +1,373 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for MPS Multi-phase Digital VR Controllers
> + *
> + * Copyright (C) 2020 Nvidia Technologies Ltd.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include "pmbus.h"
> +
> +/* Vendor specific registers. */
> +#define MP2888_MFR_SYS_CONFIG	0x44
> +#define MP2888_MFR_READ_CS1_2	0x73
> +#define MP2888_MFR_READ_CS3_4	0x74
> +#define MP2888_MFR_READ_CS5_6	0x75
> +#define MP2888_MFR_READ_CS7_8	0x76
> +#define MP2888_MFR_READ_CS9_10	0x77
> +#define MP2888_MFR_VR_CONFIG1	0xe1
> +
> +#define MP2888_TOTAL_CURRENT_RESOLUTION	BIT(3)
> +#define MP2888_PHASE_CURRENT_RESOLUTION	BIT(4)
> +#define MP2888_DRMOS_KCS		GENMASK(2, 0)
> +#define MP2888_VIN_LIMIT_UNIT		8
> +#define MP2888_VIN_UNIT			3125
> +#define MP2888_TEMP_UNIT		10
> +#define MP2888_MAX_PHASE		10
> +
> +struct mp2888_data {
> +	struct pmbus_driver_info info;
> +	int total_curr_resolution;
> +	int phase_curr_resolution;
> +	int curr_sense_gain;
> +};
> +
> +#define to_mp2888_data(x)  container_of(x, struct mp2888_data, info)
> +
> +static int mp2888_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	switch (reg) {
> +	case PMBUS_VOUT_MODE:
> +		/* Enforce VOUT direct format. */
> +		return PB_VOUT_MODE_DIRECT;
> +	default:
> +		return -ENODATA;
> +	}
> +}
> +
> +/* Convert linear sensor values to milli- or micro-units depending on sensor type. */
> +static s64 mp2888_reg2data_linear11(int data, enum pmbus_sensor_classes class)
> +{
> +	s16 exponent;
> +	s32 mantissa;
> +	s64 val;
> +
> +	exponent = ((s16)data) >> 11;
> +	mantissa = ((s16)((data & 0x7ff) << 5)) >> 5;
> +	val = mantissa;
> +
> +	/* Scale result to micro-units for power sensors. */
> +	if (class == PSC_POWER)
> +		val = val * 1000LL;
> +
> +	if (exponent >= 0)
> +		val <<= exponent;
> +	else
> +		val >>= -exponent;
> +
> +	return val;
> +}
> +
> +static int
> +mp2888_current_sense_gain_and_resolution_get(struct i2c_client *client, struct mp2888_data *data)
> +{
> +	int ret;
> +
> +	/*
> +	 * Obtain DrMOS current sense gain of power stage from the register
> +	 * , bits 0-2. The value is selected as below:
> +	 * 00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A. Other
> +	 * values are reserved.
> +	 */
> +	ret = i2c_smbus_read_word_data(client, MP2888_MFR_SYS_CONFIG);
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (ret & MP2888_DRMOS_KCS) {
> +	case 0:
> +		data->curr_sense_gain = 85;
> +		break;
> +	case 1:
> +		data->curr_sense_gain = 97;
> +		break;
> +	case 2:
> +		data->curr_sense_gain = 100;
> +		break;
> +	case 3:
> +		data->curr_sense_gain = 50;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Obtain resolution selector for total and phase current report and protection.
> +	 * 0: original resolution; 1: half resolution (in such case phase current value should
> +	 * be doubled.
> +	 */
> +	data->total_curr_resolution = (ret & MP2888_TOTAL_CURRENT_RESOLUTION) >> 3;
> +	data->phase_curr_resolution = (ret & MP2888_PHASE_CURRENT_RESOLUTION) >> 4;
> +
> +	return 0;
> +}
> +
> +static int
> +mp2888_read_phase(struct i2c_client *client, struct mp2888_data *data, int page, int phase, u8 reg)
> +{
> +	int ret;
> +
> +	ret = pmbus_read_word_data(client, page, phase, reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!((phase + 1) % 2))
> +		ret >>= 8;
> +	ret &= 0xff;
> +
> +	/*
> +	 * Output value is calculated as: (READ_CSx / 80 – 1.23) / (Kcs * Rcs)
> +	 * where:
> +	 * - Kcs is the DrMOS current sense gain of power stage, which is obtained from the
> +	 *   register MP2888_MFR_VR_CONFIG1, bits 13-12 with the following selection of DrMOS
> +	 *   (data->curr_sense_gain):
> +	 *   00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A.
> +	 * - Rcs is the internal phase current sense resistor. This parameter depends on hardware
> +	 *   assembly. By default it is set to 1kΩ. In case of different assembly, user should
> +	 *   scale this parameter by dividing it by Rcs.
> +	 * If phase current resolution bit is set to 1, READ_CSx value should be doubled.
> +	 * Note, that current phase sensing, providing by the device is not accurate. This is
> +	 * because sampling of current occurrence of bit weight has a big deviation, especially for
> +	 * light load.
> +	 */
> +	if (data->phase_curr_resolution)
> +		ret *= 2;
> +	return DIV_ROUND_CLOSEST(ret * 100 - 9800, data->curr_sense_gain);
> +}
> +
> +static int
> +mp2888_read_phases(struct i2c_client *client, struct mp2888_data *data, int page, int phase)
> +{
> +	int ret;
> +
> +	switch (phase) {
> +	case 0 ... 1:
> +		ret = mp2888_read_phase(client, data, page, phase, MP2888_MFR_READ_CS1_2);
> +		break;
> +	case 2 ... 3:
> +		ret = mp2888_read_phase(client, data, page, phase, MP2888_MFR_READ_CS3_4);
> +		break;
> +	case 4 ... 5:
> +		ret = mp2888_read_phase(client, data, page, phase, MP2888_MFR_READ_CS5_6);
> +		break;
> +	case 6 ... 7:
> +		ret = mp2888_read_phase(client, data, page, phase, MP2888_MFR_READ_CS7_8);
> +		break;
> +	case 8 ... 9:
> +		ret = mp2888_read_phase(client, data, page, phase, MP2888_MFR_READ_CS9_10);
> +		break;
> +	default:
> +		return -ENODATA;
> +	}
> +	return ret;
> +}
> +
> +static int mp2888_read_word_data(struct i2c_client *client, int page, int phase, int reg)
> +{
> +	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
> +	struct mp2888_data *data = to_mp2888_data(info);
> +	s64 val;
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_READ_VIN:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret <= 0)
> +			return ret;
> +		/*
> +		 * READ_VIN register has unused bits 15:10 with fixed value 111011b. Clear these
> +		 * bits and scale with coefficient 0.03125.
> +		 */
> +		val = mp2888_reg2data_linear11(ret &= GENMASK(9, 0), PSC_VOLTAGE_IN);
> +		ret = DIV_ROUND_CLOSEST(val * MP2888_VIN_UNIT, 100000);

This needs to be DIV_ROUND_CLOSEST_ULL().

Note that I do wonder if s64 is really needed here. The return value is supposed
to fit into a 16-bit value, after all. In this specific case, the passed
parameter already has bit 10..15 cleared, so the return value will always
be the same value as passed to mp2888_reg2data_linear11(). This means the
maximum value, in reality, is 1023 * 3125, which is then divided by 100000.
This in turn means the code looses lots of precision since, effectively,
the 10 bit value range is reduced to about 5 bit.

Please simplify in a way that doesn't loose precision.


> +		break;
> +	case PMBUS_READ_TEMPERATURE_1:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +		val = mp2888_reg2data_linear11(ret, PSC_TEMPERATURE);
> +		ret = DIV_ROUND_CLOSEST(val, MP2888_TEMP_UNIT);

Same here. The divide operation causes a loss in precision which
we really should avoid.

> +		break;
> +	case PMBUS_READ_IOUT:
> +		if (phase != 0xff)
> +			return mp2888_read_phases(client, data, page, phase);
> +
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +		/*
> +		 * READ_IOUT register has unused bits 15:12 with fixed value 1110b. Clear these
> +		 * bits and scale with total current resolution. Data is provided in direct format.
> +		 */

Doesn't that suggest LINEAR11 format ? 1110b in bits 15:12 is exponent -2,
after all.

> +		ret &= GENMASK(11, 0);
> +		ret = data->total_curr_resolution ? DIV_ROUND_CLOSEST(ret, 2) :
> +		      DIV_ROUND_CLOSEST(ret, 4);
> +		break;
> +	case PMBUS_READ_POUT:
> +	case PMBUS_READ_PIN:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +		val = mp2888_reg2data_linear11(ret, PSC_POWER);
> +		ret = data->total_curr_resolution ? val : DIV_ROUND_CLOSEST(val, 2);

Another use case for DIV_ROUND_CLOSEST_ULL. 

> +		break;
> +	/*
> +	 * The below registers are not implemented by device or implemented not according to the
> +	 * spec. Skip all of them to avoid exposing non-relevant inputs to sysfs.
> +	 */
> +	case PMBUS_OT_FAULT_LIMIT:
> +	case PMBUS_UT_WARN_LIMIT:
> +	case PMBUS_UT_FAULT_LIMIT:
> +	case PMBUS_VIN_UV_FAULT_LIMIT:
> +	case PMBUS_VOUT_UV_WARN_LIMIT:
> +	case PMBUS_VOUT_OV_WARN_LIMIT:
> +	case PMBUS_VOUT_UV_FAULT_LIMIT:
> +	case PMBUS_VOUT_OV_FAULT_LIMIT:
> +	case PMBUS_VIN_OV_WARN_LIMIT:
> +	case PMBUS_IOUT_OC_LV_FAULT_LIMIT:
> +	case PMBUS_IOUT_OC_WARN_LIMIT:
> +	case PMBUS_IOUT_OC_FAULT_LIMIT:
> +	case PMBUS_IOUT_UC_FAULT_LIMIT:
> +	case PMBUS_POUT_OP_FAULT_LIMIT:
> +	case PMBUS_POUT_OP_WARN_LIMIT:
> +	case PMBUS_PIN_OP_WARN_LIMIT:
> +	case PMBUS_MFR_VIN_MIN:
> +	case PMBUS_MFR_VIN_MAX:
> +	case PMBUS_MFR_VOUT_MAX:
> +	case PMBUS_MFR_IIN_MAX:
> +	case PMBUS_MFR_IOUT_MAX:
> +	case PMBUS_MFR_PIN_MAX:
> +	case PMBUS_MFR_POUT_MAX:
> +	case PMBUS_MFR_MAX_TEMP_1:
> +		return -ENXIO;
> +	default:
> +		return -ENODATA;
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +mp2888_identify_multiphase(struct i2c_client *client, struct mp2888_data *data,
> +			   struct pmbus_driver_info *info)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Identify multiphase number - could be from 1 to 10. */
> +	ret = i2c_smbus_read_word_data(client, MP2888_MFR_VR_CONFIG1);
> +	if (ret <= 0)
> +		return ret;
> +
> +	info->phases[0] = ret & GENMASK(3, 0);
> +
> +	/*
> +	 * The device provides a total of 10 PWM pins, and can be configured to different phase
> +	 * count applications for rail.
> +	 */
> +	if (info->phases[0] > MP2888_MAX_PHASE)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static struct pmbus_driver_info mp2888_info = {
> +	.pages = 1,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_VOLTAGE_OUT] = direct,
> +	.format[PSC_TEMPERATURE] = direct,
> +	.format[PSC_CURRENT_IN] = linear,
> +	.format[PSC_CURRENT_OUT] = direct,
> +	.format[PSC_POWER] = direct,
> +	.m[PSC_TEMPERATURE] = 1,
> +	.m[PSC_VOLTAGE_OUT] = 1,
> +	.R[PSC_VOLTAGE_OUT] = 3,
> +	.m[PSC_CURRENT_OUT] = 1,
> +	.m[PSC_POWER] = 1,
> +	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_IOUT |
> +		   PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP |
> +		   PMBUS_HAVE_POUT | PMBUS_HAVE_PIN | PMBUS_HAVE_STATUS_INPUT |
> +		   PMBUS_PHASE_VIRTUAL,
> +	.pfunc[0] = PMBUS_HAVE_IOUT,
> +	.pfunc[1] = PMBUS_HAVE_IOUT,
> +	.pfunc[2] = PMBUS_HAVE_IOUT,
> +	.pfunc[3] = PMBUS_HAVE_IOUT,
> +	.pfunc[4] = PMBUS_HAVE_IOUT,
> +	.pfunc[5] = PMBUS_HAVE_IOUT,
> +	.pfunc[6] = PMBUS_HAVE_IOUT,
> +	.pfunc[7] = PMBUS_HAVE_IOUT,
> +	.pfunc[8] = PMBUS_HAVE_IOUT,
> +	.pfunc[9] = PMBUS_HAVE_IOUT,
> +	.read_byte_data = mp2888_read_byte_data,
> +	.read_word_data = mp2888_read_word_data,
> +};
> +
> +static int mp2888_probe(struct i2c_client *client)
> +{
> +	struct pmbus_driver_info *info;
> +	struct mp2888_data *data;
> +	int ret;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct mp2888_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	memcpy(&data->info, &mp2888_info, sizeof(*info));
> +	info = &data->info;
> +
> +	/* Identify multiphase configuration. */
> +	ret = mp2888_identify_multiphase(client, data, info);
> +	if (ret)
> +		return ret;
> +
> +	/* Obtain current sense gain of power stage and current resolution. */
> +	ret = mp2888_current_sense_gain_and_resolution_get(client, data);
> +	if (ret)
> +		return ret;
> +
> +	return pmbus_do_probe(client, info);
> +}
> +
> +static const struct i2c_device_id mp2888_id[] = {
> +	{"mp2888", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, mp2888_id);
> +
> +static const struct of_device_id __maybe_unused mp2888_of_match[] = {
> +	{.compatible = "mps,mp2888"},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mp2888_of_match);
> +
> +static struct i2c_driver mp2888_driver = {
> +	.driver = {
> +		.name = "mp2888",
> +		.of_match_table = of_match_ptr(mp2888_of_match),
> +	},
> +	.probe_new = mp2888_probe,
> +	.id_table = mp2888_id,
> +};
> +
> +module_i2c_driver(mp2888_driver);
> +
> +MODULE_AUTHOR("Vadim Pasternak <vadimp@nvidia.com>");
> +MODULE_DESCRIPTION("PMBus driver for MPS MP2888 device");
> +MODULE_LICENSE("GPL");
> -- 
> 2.11.0
>