RE: [PATCH hwmon-next v4 1/2] hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller

[Vadim Pasternak <vadimp@nvidia.com>]

> -----Original Message-----
> From: Guenter Roeck <groeck7@gmail.com> On Behalf Of Guenter Roeck
> Sent: Wednesday, September 30, 2020 8:17 AM
> To: Vadim Pasternak <vadimp@nvidia.com>
> Cc: robh+dt@kernel.org; linux-hwmon@vger.kernel.org;
> devicetree@vger.kernel.org
> Subject: Re: [PATCH hwmon-next v4 1/2] hwmon: (pmbus) Add support for
> MPS Multi-phase mp2975 controller
> 
> On Sat, Sep 26, 2020 at 11:49:56PM +0300, Vadim Pasternak wrote:
> > Add support for mp295 device from Monolithic Power Systems, Inc. (MPS)
> > vendor. This is a dual-loop, digital, multi-phase controller.
> > This device:
> > - Supports two power rail.
> > - Provides 8 pulse-width modulations (PWMs), and can be configured up
> >   to 8-phase operation for rail 1 and up to 4-phase operation for rail
> >   2.
> > - Supports two pages 0 and 1 for telemetry and also pages 2 and 3 for
> >   configuration.
> > - 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>
> > ---
> > v3->v4
> >  Comments pointed out by Guenter:
> >  - Drop redundant 'return' from mp2975_identify_multiphase_rail2().
> >  - Fix phases assignment in mp2975_set_phase_rail2().
> >  - Fix range for the number of phases in mp2975_set_multiphase_rail2().
> >  - Drop mp2975_set_multiphase_rail2, call instead directly
> >    mp2975_set_phase_rail2(), since the phases range is already
> >    validated for rail 2.
> >  - Fix handling for the case of zero number of phases for rail 1 in
> >    mp2975_identify_multiphase(), which is valid case.
> >  - Simplify logic for rail1 and rail2 setting handling in
> >    mp2975_identify_multiphase().
> >  - Line length limit is now 100, but 'checkpatch' scripts is still
> >    consider it as error.
> 
> Not really. That only happens if your baseline kernel version is too old.
> ee upstream commit bdc48fa11e46 ("checkpatch/coding-style: deprecate 80-
> column warning").

Oops. I really missed it.

> 
> >  - Modify 'switch' statement in mp2975_current_sense_gain_get().
> >  - Fix misspelled comment in mp2975_probe().
> > v1->v2
> >  Comments pointed out by Guenter:
> >  - Add doc fail to the patch#1 (it was sent as separate patch).
> >  - Use standard define for VOUT mode format.
> >  - Simplify logic in mp2975_read_phase().
> >  - Simplify calculation of phase current in mp2975_read_phase().
> >  - Modify return code handling in mp2975_read_word_data().
> >  - Add missed error handling in mp2975_read_word_data().
> >  - Drop 'fallthrough;' in  mp2975_read_word_data().
> >  - Handle error code in mp2975_identify_multiphase_rail2().
> >  - Handle error code in mp2975_identify_multiphase().
> >  - Drop 'goto' in mp2975_vout_per_rail_config_get() and mp2975_probe().
> > ---
> >  Documentation/hwmon/mp2975.rst | 116 +++++++
> >  drivers/hwmon/pmbus/Kconfig    |   9 +
> >  drivers/hwmon/pmbus/Makefile   |   1 +
> >  drivers/hwmon/pmbus/mp2975.c   | 772
> +++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 898 insertions(+)
> >  create mode 100644 Documentation/hwmon/mp2975.rst  create mode
> 100644
> > drivers/hwmon/pmbus/mp2975.c
> >
> > diff --git a/Documentation/hwmon/mp2975.rst
> > b/Documentation/hwmon/mp2975.rst new file mode 100644 index
> > 000000000000..5b0609c62f48
> > --- /dev/null
> > +++ b/Documentation/hwmon/mp2975.rst
> > @@ -0,0 +1,116 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +Kernel driver mp2975
> > +====================
> > +
> > +Supported chips:
> > +
> > +  * MPS MP12254
> > +
> > +    Prefix: 'mp2975'
> > +
> > +Author:
> > +
> > +	Vadim Pasternak <vadimp@nvidia.com>
> > +
> > +Description
> > +-----------
> > +
> > +This driver implements support for Monolithic Power Systems, Inc.
> > +(MPS) vendor dual-loop, digital, multi-phase controller MP2975.
> > +
> > +This device:
> > +- Supports up to two power rail.
> > +- Provides 8 pulse-width modulations (PWMs), and can be configured up
> > +  to 8-phase operation for rail 1 and up to 4-phase operation for
> > +rail
> > +  2.
> > +- Supports two pages 0 and 1 for telemetry and also pages 2 and 3 for
> > +  configuration.
> > +- 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.
> > +
> > +Device supports:
> > +- SVID interface.
> > +- AVSBus interface.
> > +
> > +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.
> > +Device supports VID and direct formats for reading output voltage.
> > +The below VID modes are supported: VR12, VR13, IMVP9.
> > +
> > +The driver provides the next attributes for the current:
> > +- for current in: input, maximum alarm;
> > +- for current out input, maximum alarm and highest values;
> > +- for phase current: input and label.
> > +attributes.
> > +The driver exports the following attributes via the 'sysfs' files,
> > +where
> > +- 'n' is number of telemetry pages (from 1 to 2);
> > +- 'k' is number of configured phases (from 1 to 8);
> > +- indexes 1, 1*n for "iin";
> > +- indexes n+1, n+2 for "iout";
> > +- indexes 2*n+1 ... 2*n + k for phases.
> > +
> > +**curr[1-{2n}]_alarm**
> > +
> > +**curr[{n+1}-{n+2}]_highest**
> > +
> > +**curr[1-{2n+k}]_input**
> > +
> > +**curr[1-{2n+k}]_label**
> > +
> > +The driver provides the next attributes for the voltage:
> > +- for voltage in: input, high critical threshold, high critical
> > +alarm, all only
> > +  from page 0;
> > +- for voltage out: input, low and high critical thresholds, low and
> > +high
> > +  critical alarms, from pages 0 and 1; The driver exports the
> > +following attributes via the 'sysfs' files, where
> > +- 'n' is number of telemetry pages (from 1 to 2);
> > +- indexes 1 for "iin";
> > +- indexes n+1, n+2 for "vout";
> > +
> > +**in[1-{2n+1}]_crit**
> > +
> > +**in[1-{2n+1}]_crit_alarm**
> > +
> > +**in[1-{2n+1}]_input**
> > +
> > +**in[1-{2n+1}]_label**
> > +
> > +**in[2-{n+1}]_lcrit**
> > +
> > +**in[2-{n+1}1_lcrit_alarm**
> > +
> > +The driver provides the next attributes for the power:
> > +- for power in alarm and input.
> > +- for power out: highest and input.
> > +The driver exports the following attributes via the 'sysfs' files,
> > +where
> > +- 'n' is number of telemetry pages (from 1 to 2);
> > +- indexes 1 for "pin";
> > +- indexes n+1, n+2 for "pout";
> > +
> > +**power1_alarm**
> > +
> > +**power[2-{n+1}]_highest**
> > +
> > +**power[1-{2n+1}]_input**
> > +
> > +**power[1-{2n+1}]_label**
> > +
> > +The driver provides the next attributes for the temperature (only from page
> 0):
> > +
> > +
> > +**temp1_crit**
> > +
> > +**temp1_crit_alarm**
> > +
> > +**temp1_input**
> > +
> > +**temp1_max**
> > +
> > +**temp1_max_alarm**
> > diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> > index e35db489b76f..1e6157e85437 100644
> > --- a/drivers/hwmon/pmbus/Kconfig
> > +++ b/drivers/hwmon/pmbus/Kconfig
> > @@ -200,6 +200,15 @@ config SENSORS_MAX8688
> >  	  This driver can also be built as a module. If so, the module will
> >  	  be called max8688.
> >
> > +config SENSORS_MP2975
> > +	tristate "MPS MP2975"
> > +	help
> > +	  If you say yes here you get hardware monitoring support for MPS
> > +	  MP2975 Dual Loop Digital Multi-Phase Controller.
> > +
> > +	  This driver can also be built as a module. If so, the module will
> > +	  be called mp2975.
> > +
> >  config SENSORS_PXE1610
> >  	tristate "Infineon PXE1610"
> >  	help
> > diff --git a/drivers/hwmon/pmbus/Makefile
> > b/drivers/hwmon/pmbus/Makefile index c4b15db996ad..0e2832e73cfc
> 100644
> > --- a/drivers/hwmon/pmbus/Makefile
> > +++ b/drivers/hwmon/pmbus/Makefile
> > @@ -23,6 +23,7 @@ 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-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
> >  obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
> >  obj-$(CONFIG_SENSORS_TPS40422)	+= tps40422.o
> >  obj-$(CONFIG_SENSORS_TPS53679)	+= tps53679.o
> > diff --git a/drivers/hwmon/pmbus/mp2975.c
> > b/drivers/hwmon/pmbus/mp2975.c new file mode 100644 index
> > 000000000000..f2f3e74c4953
> > --- /dev/null
> > +++ b/drivers/hwmon/pmbus/mp2975.c
> > @@ -0,0 +1,772 @@
> > +// 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 MP2975_MFR_APS_HYS_R2		0x0d
> > +#define MP2975_MFR_SLOPE_TRIM3		0x1d
> > +#define MP2975_MFR_VR_MULTI_CONFIG_R1	0x0d
> > +#define MP2975_MFR_VR_MULTI_CONFIG_R2	0x1d
> > +#define MP2975_MFR_APS_DECAY_ADV	0x56
> > +#define MP2975_MFR_DC_LOOP_CTRL		0x59
> > +#define MP2975_MFR_OCP_UCP_PHASE_SET	0x65
> > +#define MP2975_MFR_VR_CONFIG1		0x68
> > +#define MP2975_MFR_READ_CS1_2		0x82
> > +#define MP2975_MFR_READ_CS3_4		0x83
> > +#define MP2975_MFR_READ_CS5_6		0x84
> > +#define MP2975_MFR_READ_CS7_8		0x85
> > +#define MP2975_MFR_READ_CS9_10		0x86
> > +#define MP2975_MFR_READ_CS11_12		0x87
> > +#define MP2975_MFR_READ_IOUT_PK		0x90
> > +#define MP2975_MFR_READ_POUT_PK		0x91
> > +#define MP2975_MFR_READ_VREF_R1		0xa1
> > +#define MP2975_MFR_READ_VREF_R2		0xa3
> > +#define MP2975_MFR_OVP_TH_SET		0xe5
> > +#define MP2975_MFR_UVP_SET		0xe6
> > +
> > +#define MP2975_VOUT_FORMAT		BIT(15)
> > +#define MP2975_VID_STEP_SEL_R1		BIT(4)
> > +#define MP2975_IMVP9_EN_R1		BIT(13)
> > +#define MP2975_VID_STEP_SEL_R2		BIT(3)
> > +#define MP2975_IMVP9_EN_R2		BIT(12)
> > +#define MP2975_PRT_THRES_DIV_OV_EN	BIT(14)
> > +#define MP2975_DRMOS_KCS		GENMASK(13, 12)
> > +#define MP2975_PROT_DEV_OV_OFF		10
> > +#define MP2975_PROT_DEV_OV_ON		5
> > +#define MP2975_SENSE_AMPL		BIT(11)
> > +#define MP2975_SENSE_AMPL_UNIT		1
> > +#define MP2975_SENSE_AMPL_HALF		2
> > +#define MP2975_VIN_UV_LIMIT_UNIT	8
> > +
> > +#define MP2975_MAX_PHASE_RAIL1	8
> > +#define MP2975_MAX_PHASE_RAIL2	4
> > +#define MP2975_PAGE_NUM		2
> > +
> > +#define MP2975_RAIL2_FUNC	(PMBUS_HAVE_VOUT |
> PMBUS_HAVE_STATUS_VOUT | \
> > +				 PMBUS_HAVE_IOUT |
> PMBUS_HAVE_STATUS_IOUT | \
> > +				 PMBUS_PHASE_VIRTUAL)
> > +
> > +struct mp2975_data {
> > +	struct pmbus_driver_info info;
> > +	int vout_scale;
> > +	int vid_step[MP2975_PAGE_NUM];
> > +	int vref[MP2975_PAGE_NUM];
> > +	int vref_off[MP2975_PAGE_NUM];
> > +	int vout_max[MP2975_PAGE_NUM];
> > +	int vout_ov_fixed[MP2975_PAGE_NUM];
> > +	int vout_format[MP2975_PAGE_NUM];
> > +	int curr_sense_gain[MP2975_PAGE_NUM]; };
> > +
> > +#define to_mp2975_data(x)  container_of(x, struct mp2975_data, info)
> > +
> > +static int mp2975_read_byte_data(struct i2c_client *client, int page,
> > +int reg) {
> > +	switch (reg) {
> > +	case PMBUS_VOUT_MODE:
> > +		/*
> > +		 * Enforce VOUT direct format, since device allows to set the
> > +		 * different formats for the different rails. Conversion from
> > +		 * VID to direct provided by driver internally, in case it is
> > +		 * necessary.
> > +		 */
> > +		return PB_VOUT_MODE_DIRECT;
> > +	default:
> > +		return -ENODATA;
> > +	}
> > +}
> > +
> > +static int
> > +mp2975_read_word_helper(struct i2c_client *client, int page, int phase, u8
> reg,
> > +			u16 mask)
> > +{
> > +	int ret = pmbus_read_word_data(client, page, phase, reg);
> > +
> > +	return (ret > 0) ? ret & mask : ret; }
> > +
> > +static int
> > +mp2975_vid2direct(int vrf, int val)
> > +{
> > +	switch (vrf) {
> > +	case vr12:
> > +		if (val >= 0x01)
> > +			return 250 + (val - 1) * 5;
> > +		break;
> > +	case vr13:
> > +		if (val >= 0x01)
> > +			return 500 + (val - 1) * 10;
> > +		break;
> > +	case imvp9:
> > +		if (val >= 0x01)
> > +			return 200 + (val - 1) * 10;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_read_phase(struct i2c_client *client, struct mp2975_data *data,
> > +		  int page, int phase, u8 reg)
> > +{
> > +	int ph_curr, ret;
> > +
> > +	ret = pmbus_read_word_data(client, page, phase, reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (!((phase + 1) % MP2975_PAGE_NUM))
> > +		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 MP2975_MFR_VR_CONFIG1, bits 13-12
> with
> > +	 *   the following selection of DrMOS (data->curr_sense_gain[page]):
> > +	 *   00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A.
> > +	 * - Rcs is the internal phase current sense resistor which is constant
> > +	 *   value 1kΩ.
> > +	 */
> > +	ph_curr = ret * 100 - 9800;
> > +
> > +	/*
> > +	 * Current phase sensing, providing by the device is not accurate
> > +	 * for the light load. This because sampling of current occurrence of
> > +	 * bit weight has a big deviation for light load. For handling such
> > +	 * case phase current is represented as the maximum between the
> value
> > +	 * calculated  above and total rail current divided by number phases.
> > +	 */
> > +	ret = pmbus_read_word_data(client, page, phase,
> PMBUS_READ_IOUT);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return max_t(int, DIV_ROUND_CLOSEST(ret, data->info.phases[page]),
> > +		     DIV_ROUND_CLOSEST(ph_curr, data-
> >curr_sense_gain[page])); }
> > +
> > +static int
> > +mp2975_read_phases(struct i2c_client *client, struct mp2975_data *data,
> > +		   int page, int phase)
> > +{
> > +	int ret;
> > +
> > +	if (page) {
> > +		switch (phase) {
> > +		case 0 ... 1:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +						MP2975_MFR_READ_CS7_8);
> > +			break;
> > +		case 2 ... 3:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +
> 	MP2975_MFR_READ_CS9_10);
> > +			break;
> > +		case 4 ... 5:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +
> 	MP2975_MFR_READ_CS11_12);
> > +			break;
> > +		default:
> > +			return -ENODATA;
> > +		}
> > +	} else {
> > +		switch (phase) {
> > +		case 0 ... 1:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +						MP2975_MFR_READ_CS1_2);
> > +			break;
> > +		case 2 ... 3:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +						MP2975_MFR_READ_CS3_4);
> > +			break;
> > +		case 4 ... 5:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +						MP2975_MFR_READ_CS5_6);
> > +			break;
> > +		case 6 ... 7:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +						MP2975_MFR_READ_CS7_8);
> > +			break;
> > +		case 8 ... 9:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +
> 	MP2975_MFR_READ_CS9_10);
> > +			break;
> > +		case 10 ... 11:
> > +			ret = mp2975_read_phase(client, data, page, phase,
> > +
> 	MP2975_MFR_READ_CS11_12);
> > +			break;
> > +		default:
> > +			return -ENODATA;
> > +		}
> > +	}
> > +	return ret;
> > +}
> > +
> > +static int mp2975_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 mp2975_data *data = to_mp2975_data(info);
> > +	int ret;
> > +
> > +	switch (reg) {
> > +	case PMBUS_OT_FAULT_LIMIT:
> > +		ret = mp2975_read_word_helper(client, page, phase, reg,
> > +					      GENMASK(7, 0));
> > +		break;
> > +	case PMBUS_VIN_OV_FAULT_LIMIT:
> > +		ret = mp2975_read_word_helper(client, page, phase, reg,
> > +					      GENMASK(7, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ret = DIV_ROUND_CLOSEST(ret,
> MP2975_VIN_UV_LIMIT_UNIT);
> > +		break;
> > +	case PMBUS_VOUT_OV_FAULT_LIMIT:
> > +		/*
> > +		 * Register provides two values for over-voltage protection
> > +		 * threshold for fixed (ovp2) and tracking (ovp1) modes. The
> > +		 * minimum of these two values is provided as over-voltage
> > +		 * fault alarm.
> > +		 */
> > +		ret = mp2975_read_word_helper(client, page, phase,
> > +					      MP2975_MFR_OVP_TH_SET,
> > +					      GENMASK(2, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ret = min_t(int, data->vout_max[page] + 50 * (ret + 1),
> > +			    data->vout_ov_fixed[page]);
> > +		break;
> > +	case PMBUS_VOUT_UV_FAULT_LIMIT:
> > +		ret = mp2975_read_word_helper(client, page, phase,
> > +					      MP2975_MFR_UVP_SET,
> > +					      GENMASK(2, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ret = DIV_ROUND_CLOSEST(data->vref[page] * 10 - 50 *
> > +					(ret + 1) * data->vout_scale, 10);
> > +		break;
> > +	case PMBUS_READ_VOUT:
> > +		ret = mp2975_read_word_helper(client, page, phase, reg,
> > +					      GENMASK(11, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/*
> > +		 * READ_VOUT can be provided in VID or direct format. The
> > +		 * format type is specified by bit 15 of the register
> > +		 * MP2975_MFR_DC_LOOP_CTRL. The driver enforces VOUT
> direct
> > +		 * format, since device allows to set the different formats for
> > +		 * the different rails and also all VOUT limits registers are
> > +		 * provided in a direct format. In case format is VID - convert
> > +		 * to direct.
> > +		 */
> > +		if (data->vout_format[page] == vid)
> > +			ret = mp2975_vid2direct(info->vrm_version[page],
> ret);
> > +		break;
> > +	case PMBUS_VIRT_READ_POUT_MAX:
> > +		ret = mp2975_read_word_helper(client, page, phase,
> > +					      MP2975_MFR_READ_POUT_PK,
> > +					      GENMASK(12, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ret = DIV_ROUND_CLOSEST(ret, 4);
> > +		break;
> > +	case PMBUS_VIRT_READ_IOUT_MAX:
> > +		ret = mp2975_read_word_helper(client, page, phase,
> > +					      MP2975_MFR_READ_IOUT_PK,
> > +					      GENMASK(12, 0));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		ret = DIV_ROUND_CLOSEST(ret, 4);
> > +		break;
> > +	case PMBUS_READ_IOUT:
> > +		ret = mp2975_read_phases(client, data, page, phase);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		break;
> > +	case PMBUS_UT_WARN_LIMIT:
> > +	case PMBUS_UT_FAULT_LIMIT:
> > +	case PMBUS_VIN_UV_WARN_LIMIT:
> > +	case PMBUS_VIN_UV_FAULT_LIMIT:
> > +	case PMBUS_VOUT_UV_WARN_LIMIT:
> > +	case PMBUS_VOUT_OV_WARN_LIMIT:
> > +	case PMBUS_VIN_OV_WARN_LIMIT:
> > +	case PMBUS_IIN_OC_FAULT_LIMIT:
> > +	case PMBUS_IOUT_OC_LV_FAULT_LIMIT:
> > +	case PMBUS_IIN_OC_WARN_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:
> > +		return -ENXIO;
> > +	default:
> > +		return -ENODATA;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static int mp2975_identify_multiphase_rail2(struct i2c_client
> > +*client) {
> > +	int ret;
> > +
> > +	/*
> > +	 * Identify multiphase for rail 2 - could be from 0 to 4.
> > +	 * In case phase number is zero – only page zero is supported
> > +	 */
> > +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Identify multiphase for rail 2 - could be from 0 to 4. */
> > +	ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_VR_MULTI_CONFIG_R2);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret &= GENMASK(2, 0);
> > +	return (ret >= 4) ? 4 : ret;
> > +}
> > +
> > +static void mp2975_set_phase_rail1(struct pmbus_driver_info *info) {
> > +	int i;
> > +
> > +	for (i = 0 ; i < info->phases[0]; i++)
> > +		info->pfunc[i] = PMBUS_HAVE_IOUT;
> > +}
> > +
> > +static void
> > +mp2975_set_phase_rail2(struct pmbus_driver_info *info, int
> > +num_phases) {
> > +	int i;
> > +
> > +	/* Set phases for rail 2 from upper to lower. */
> > +	for (i = 1; i <= num_phases; i++)
> > +		info->pfunc[MP2975_MAX_PHASE_RAIL1 - i] =
> PMBUS_HAVE_IOUT; }
> > +
> > +static int
> > +mp2975_identify_multiphase(struct i2c_client *client, struct mp2975_data
> *data,
> > +			   struct pmbus_driver_info *info) {
> > +	int num_phases2, ret;
> > +
> > +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Identify multiphase for rail 1 - could be from 1 to 8. */
> > +	ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_VR_MULTI_CONFIG_R1);
> > +	if (ret <= 0)
> > +		return ret;
> > +
> > +	info->phases[0] = ret & GENMASK(3, 0);
> > +
> > +	/*
> > +	 * The device provides a total of 8 PWM pins, and can be configured
> > +	 * to different phase count applications for rail 1 and rail 2.
> > +	 * Rail 1 can be set to 8 phases, while rail 2 can only be set to 4
> > +	 * phases at most. When rail 1’s phase count is configured as 0, rail
> > +	 * 1 operates with 1-phase DCM. When rail 2 phase count is configured
> > +	 * as 0, rail 2 is disabled.
> > +	 */
> > +	if (info->phases[0] > MP2975_MAX_PHASE_RAIL1)
> > +		return -EINVAL;
> > +
> > +	mp2975_set_phase_rail1(info);
> > +	num_phases2 = min(MP2975_MAX_PHASE_RAIL1 - info->phases[0],
> > +			  MP2975_MAX_PHASE_RAIL2);
> > +	if (info->phases[1] && info->phases[1] <= num_phases2)
> > +		mp2975_set_phase_rail2(info, num_phases2);
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_identify_vid(struct i2c_client *client, struct mp2975_data *data,
> > +		    struct pmbus_driver_info *info, u32 reg, int page,
> > +		    u32 imvp_bit, u32 vr_bit)
> > +{
> > +	int ret;
> > +
> > +	/* Identify VID mode and step selection. */
> > +	ret = i2c_smbus_read_word_data(client, reg);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (ret & imvp_bit) {
> > +		info->vrm_version[page] = imvp9;
> > +		data->vid_step[page] = MP2975_PROT_DEV_OV_OFF;
> > +	} else if (ret & vr_bit) {
> > +		info->vrm_version[page] = vr12;
> > +		data->vid_step[page] = MP2975_PROT_DEV_OV_ON;
> > +	} else {
> > +		info->vrm_version[page] = vr13;
> > +		data->vid_step[page] = MP2975_PROT_DEV_OV_OFF;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_identify_rails_vid(struct i2c_client *client, struct mp2975_data
> *data,
> > +			  struct pmbus_driver_info *info)
> > +{
> > +	int ret;
> > +
> > +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Identify VID mode for rail 1. */
> > +	ret = mp2975_identify_vid(client, data, info,
> > +				  MP2975_MFR_VR_MULTI_CONFIG_R1, 0,
> > +				  MP2975_IMVP9_EN_R1,
> MP2975_VID_STEP_SEL_R1);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Identify VID mode for rail 2, if connected. */
> > +	if (info->phases[1])
> > +		ret = mp2975_identify_vid(client, data, info,
> > +
> MP2975_MFR_VR_MULTI_CONFIG_R2, 1,
> > +					  MP2975_IMVP9_EN_R2,
> > +					  MP2975_VID_STEP_SEL_R2);
> > +	return ret;
> > +}
> > +
> > +static int
> > +mp2975_current_sense_gain_get(struct i2c_client *client,
> > +			      struct mp2975_data *data)
> > +{
> > +	int i, ret;
> > +
> > +	/*
> > +	 * Obtain DrMOS current sense gain of power stage from the register
> > +	 * MP2975_MFR_VR_CONFIG1, bits 13-12. The value is selected as
> below:
> > +	 * 00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A. Other
> > +	 * values are invalid.
> > +	 */
> > +	for (i = 0 ; i < data->info.pages; i++) {
> > +		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
> > +		if (ret < 0)
> > +			return ret;
> > +		ret = i2c_smbus_read_word_data(client,
> > +					       MP2975_MFR_VR_CONFIG1);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		switch ((ret & MP2975_DRMOS_KCS) >> 12) {
> > +		case 0:
> > +			data->curr_sense_gain[i] = 50;
> > +			break;
> > +		case 1:
> > +			data->curr_sense_gain[i] = 85;
> > +			break;
> > +		case 2:
> > +			data->curr_sense_gain[i] = 97;
> > +			break;
> > +		default:
> > +			data->curr_sense_gain[i] = 100;
> > +			break;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_vref_get(struct i2c_client *client, struct mp2975_data *data,
> > +		struct pmbus_driver_info *info)
> > +{
> > +	int ret;
> > +
> > +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 3);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Get voltage reference value for rail 1. */
> > +	ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_READ_VREF_R1);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	data->vref[0] = ret * data->vid_step[0];
> > +
> > +	/* Get voltage reference value for rail 2, if connected. */
> > +	if (data->info.pages == MP2975_PAGE_NUM) {
> > +		ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_READ_VREF_R2);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		data->vref[1] = ret * data->vid_step[1];
> > +	}
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_vref_offset_get(struct i2c_client *client, struct mp2975_data
> *data,
> > +		       int page)
> > +{
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_word_data(client, MP2975_MFR_OVP_TH_SET);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	switch ((ret & GENMASK(5, 3)) >> 3) {
> > +	case 1:
> > +		data->vref_off[page] = 140;
> > +		break;
> > +	case 2:
> > +		data->vref_off[page] = 220;
> > +		break;
> > +	case 4:
> > +		data->vref_off[page] = 400;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_vout_max_get(struct i2c_client *client, struct mp2975_data *data,
> > +		    struct pmbus_driver_info *info, int page) {
> > +	int ret;
> > +
> > +	/* Get maximum reference voltage of VID-DAC in VID format. */
> > +	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_MAX);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	data->vout_max[page] = mp2975_vid2direct(info->vrm_version[page],
> ret &
> > +						 GENMASK(8, 0));
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_identify_vout_format(struct i2c_client *client,
> > +			    struct mp2975_data *data, int page) {
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_DC_LOOP_CTRL);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (ret & MP2975_VOUT_FORMAT)
> > +		data->vout_format[page] = vid;
> > +	else
> > +		data->vout_format[page] = direct;
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_vout_ov_scale_get(struct i2c_client *client, struct mp2975_data
> *data,
> > +			 struct pmbus_driver_info *info)
> > +{
> > +	int thres_dev, sense_ampl, ret;
> > +
> > +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/*
> > +	 * Get divider for over- and under-voltage protection thresholds
> > +	 * configuration from the Advanced Options of Auto Phase Shedding
> and
> > +	 * decay register.
> > +	 */
> > +	ret = i2c_smbus_read_word_data(client,
> MP2975_MFR_APS_DECAY_ADV);
> > +	if (ret >= 0)
> > +		thres_dev = ret & MP2975_PRT_THRES_DIV_OV_EN ?
> > +			    MP2975_PROT_DEV_OV_ON :
> MP2975_PROT_DEV_OV_OFF;
> > +	else
> > +		return ret;
> 
> Why not the usual
> 	if (ret < 0)
> 		return ret;
> 	thres_dev = ret & MP2975_PRT_THRES_DIV_OV_EN ?
> 		    MP2975_PROT_DEV_OV_ON :
> MP2975_PROT_DEV_OV_OFF;
> 
> > +
> > +	/* Select the gain of remote sense amplifier. */
> > +	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_SCALE_LOOP);
> > +	if (ret >= 0)
> > +		sense_ampl = ret & MP2975_SENSE_AMPL ?
> MP2975_SENSE_AMPL_HALF :
> > +			     MP2975_SENSE_AMPL_UNIT;
> > +	else
> > +		return ret;
> 
> Same here. The reversed logic just makes the code difficult to read.
> 
> If you want, I can make that change and apply the patch.
> Let me know.

Thank you very much, Guenter.
I'll very appreciate if you can apply the patch with these fixes.

Thank you,
Vadim.

> 
> Guenter
> 
> > +
> > +	data->vout_scale = sense_ampl * thres_dev;
> > +
> > +	return 0;
> > +}
> > +
> > +static int
> > +mp2975_vout_per_rail_config_get(struct i2c_client *client,
> > +				struct mp2975_data *data,
> > +				struct pmbus_driver_info *info)
> > +{
> > +	int i, ret;
> > +
> > +	for (i = 0; i < data->info.pages; i++) {
> > +		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/* Obtain voltage reference offsets. */
> > +		ret = mp2975_vref_offset_get(client, data, i);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/* Obtain maximum voltage values. */
> > +		ret = mp2975_vout_max_get(client, data, info, i);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/*
> > +		 * Get VOUT format for READ_VOUT command : VID or direct.
> > +		 * Pages on same device can be configured with different
> > +		 * formats.
> > +		 */
> > +		ret = mp2975_identify_vout_format(client, data, i);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		/*
> > +		 * Set over-voltage fixed value. Thresholds are provided as
> > +		 * fixed value, and tracking value. The minimum of them are
> > +		 * exposed as over-voltage critical threshold.
> > +		 */
> > +		data->vout_ov_fixed[i] = data->vref[i] +
> > +					 DIV_ROUND_CLOSEST(data-
> >vref_off[i] *
> > +							   data->vout_scale,
> > +							   10);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static struct pmbus_driver_info mp2975_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_IIN | 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,
> > +	.read_byte_data = mp2975_read_byte_data,
> > +	.read_word_data = mp2975_read_word_data, };
> > +
> > +static int mp2975_probe(struct i2c_client *client,
> > +			const struct i2c_device_id *id)
> > +{
> > +	struct pmbus_driver_info *info;
> > +	struct mp2975_data *data;
> > +	int ret;
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(struct mp2975_data),
> > +			    GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	memcpy(&data->info, &mp2975_info, sizeof(*info));
> > +	info = &data->info;
> > +
> > +	/* Identify multiphase configuration for rail 2. */
> > +	ret = mp2975_identify_multiphase_rail2(client);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (ret) {
> > +		/* Two rails are connected. */
> > +		data->info.pages = MP2975_PAGE_NUM;
> > +		data->info.phases[1] = ret;
> > +		data->info.func[1] = MP2975_RAIL2_FUNC;
> > +	}
> > +
> > +	/* Identify multiphase configuration. */
> > +	ret = mp2975_identify_multiphase(client, data, info);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/* Identify VID setting per rail. */
> > +	ret = mp2975_identify_rails_vid(client, data, info);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Obtain current sense gain of power stage. */
> > +	ret = mp2975_current_sense_gain_get(client, data);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/* Obtain voltage reference values. */
> > +	ret = mp2975_vref_get(client, data, info);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/* Obtain vout over-voltage scales. */
> > +	ret = mp2975_vout_ov_scale_get(client, data, info);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* Obtain offsets, maximum and format for vout. */
> > +	ret = mp2975_vout_per_rail_config_get(client, data, info);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return pmbus_do_probe(client, id, info); }
> > +
> > +static const struct i2c_device_id mp2975_id[] = {
> > +	{"mp2975", 0},
> > +	{}
> > +};
> > +
> > +MODULE_DEVICE_TABLE(i2c, mp2975_id);
> > +
> > +static const struct of_device_id __maybe_unused mp2975_of_match[] = {
> > +	{.compatible = "mps,mp2975"},
> > +	{}
> > +};
> > +MODULE_DEVICE_TABLE(of, mp2975_of_match);
> > +
> > +static struct i2c_driver mp2975_driver = {
> > +	.driver = {
> > +		.name = "mp2975",
> > +		.of_match_table = of_match_ptr(mp2975_of_match),
> > +	},
> > +	.probe = mp2975_probe,
> > +	.remove = pmbus_do_remove,
> > +	.id_table = mp2975_id,
> > +};
> > +
> > +module_i2c_driver(mp2975_driver);
> > +
> > +MODULE_AUTHOR("Vadim Pasternak <vadimp@nvidia.com>");
> > +MODULE_DESCRIPTION("PMBus driver for MPS MP2975 device");
> > +MODULE_LICENSE("GPL");