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Message-ID: <1f3bc281-9bb3-4a56-8791-773e2e762513@roeck-us.net>
Date: Wed, 11 Oct 2023 07:00:44 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Antoniu Miclaus <antoniu.miclaus@...log.com>,
Jean Delvare <jdelvare@...e.com>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Jonathan Corbet <corbet@....net>, 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] drivers: hwmon: ltc2991: add driver support
On Tue, Oct 10, 2023 at 10:44:44AM +0200, Nuno Sá wrote:
> Hi Antoniu,
>
> A few more comments from me. But essentially, I think you should revisit V1 and
> Guenter's comments. I'm fairly sure you are still missing his main points...
>
Yes. And there is no change log either.
Guenter
> On Tue, 2023-10-03 at 11:00 +0300, Antoniu Miclaus wrote:
> > Add support for LTC2991 Octal I2C Voltage, Current, and Temperature
> > Monitor.
> >
> > The LTC2991 is used to monitor system temperatures, voltages and
> > currents. Through the I2C serial interface, the eight monitors can
> > individually measure supply voltages and can be paired for
> > differential measurements of current sense resistors or temperature
> > sensing transistors. Additional measurements include internal
> > temperature and internal VCC.
> >
> > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > ---
> > Documentation/hwmon/index.rst | 1 +
> > Documentation/hwmon/ltc2991.rst | 43 +++
> > MAINTAINERS | 8 +
> > drivers/hwmon/Kconfig | 11 +
> > drivers/hwmon/Makefile | 1 +
> > drivers/hwmon/ltc2991.c | 479 ++++++++++++++++++++++++++++++++
> > 6 files changed, 543 insertions(+)
> > create mode 100644 Documentation/hwmon/ltc2991.rst
> > create mode 100644 drivers/hwmon/ltc2991.c
> >
> > diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> > index 88dadea85cfc..0ec96abe3f7d 100644
> > --- a/Documentation/hwmon/index.rst
> > +++ b/Documentation/hwmon/index.rst
> > @@ -121,6 +121,7 @@ Hardware Monitoring Kernel Drivers
> > ltc2947
> > ltc2978
> > ltc2990
> > + ltc2991
> > ltc3815
> > ltc4151
> > ltc4215
> > diff --git a/Documentation/hwmon/ltc2991.rst b/Documentation/hwmon/ltc2991.rst
> > new file mode 100644
> > index 000000000000..9ab29dd85012
> > --- /dev/null
> > +++ b/Documentation/hwmon/ltc2991.rst
> > @@ -0,0 +1,43 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +Kernel driver ltc2991
> > +=====================
> > +
> > +Supported chips:
> > +
> > + * Analog Devices LTC2991
> > +
> > + Prefix: 'ltc2991'
> > +
> > + Addresses scanned: I2C 0x48 - 0x4f
> > +
> > + Datasheet:
> > https://www.analog.com/media/en/technical-documentation/data-sheets/2991ff.pdf
> > +
> > +Authors:
> > +
> > + - Antoniu Miclaus <antoniu.miclaus@...log.com>
> > +
> > +
> > +Description
> > +-----------
> > +
> > +This driver supports hardware monitoring for Analog Devices LTC2991 Octal I2C
> > +Voltage, Current and Temperature Monitor.
> > +
> > +The LTC2991 is used to monitor system temperatures, voltages and currents.
> > +Through the I2C serial interface, the eight monitors can individually measure
> > +supply voltages and can be paired for differential measurements of current
> > sense
> > +resistors or temperature sensing transistors. Additional measurements include
> > +internal temperatureand internal VCC.
> > +
> > +
> > +sysfs-Interface
> > +-------------
> > +
> > +The following attributes are supported. Limits are read-only.
> > +
> > +=============== =================
> > +inX_input: voltage input
> > +currX_input: current input
> > +tempX_input: temperature input
> > +=============== =================
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index b19995690904..98dd8a8e1f84 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -12451,6 +12451,14 @@ F: drivers/hwmon/ltc2947-i2c.c
> > F: drivers/hwmon/ltc2947-spi.c
> > F: drivers/hwmon/ltc2947.h
> >
> > +LTC2991 HARDWARE MONITOR DRIVER
> > +M: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > +L: linux-hwmon@...r.kernel.org
> > +S: Supported
> > +W: https://ez.analog.com/linux-software-drivers
> > +F: Documentation/devicetree/bindings/hwmon/adi,ltc2991.yaml
> > +F: drivers/hwmon/ltc2991.c
> > +
> > LTC2983 IIO TEMPERATURE DRIVER
> > M: Nuno Sá <nuno.sa@...log.com>
> > L: linux-iio@...r.kernel.org
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index ec38c8892158..818a67328fcd 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -932,6 +932,17 @@ config SENSORS_LTC2990
> > This driver can also be built as a module. If so, the module will
> > be called ltc2990.
> >
> > +config SENSORS_LTC2991
> > + tristate "Analog Devices LTC2991"
> > + depends on I2C
> > + help
> > + If you say yes here you get support for Analog Devices LTC2991
> > + Octal I2C Voltage, Current, and Temperature Monitor. The LTC2991
> > + supports a combination of voltage, current and temperature
> > monitoring.
> > +
> > + This driver can also be built as a module. If so, the module will
> > + be called ltc2991.
> > +
> > config SENSORS_LTC2992
> > tristate "Linear Technology LTC2992"
> > depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 4ac9452b5430..f324d057535a 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC2947) += ltc2947-core.o
> > obj-$(CONFIG_SENSORS_LTC2947_I2C) += ltc2947-i2c.o
> > obj-$(CONFIG_SENSORS_LTC2947_SPI) += ltc2947-spi.o
> > obj-$(CONFIG_SENSORS_LTC2990) += ltc2990.o
> > +obj-$(CONFIG_SENSORS_LTC2991) += ltc2991.o
> > obj-$(CONFIG_SENSORS_LTC2992) += ltc2992.o
> > obj-$(CONFIG_SENSORS_LTC4151) += ltc4151.o
> > obj-$(CONFIG_SENSORS_LTC4215) += ltc4215.o
> > diff --git a/drivers/hwmon/ltc2991.c b/drivers/hwmon/ltc2991.c
> > new file mode 100644
> > index 000000000000..b5333c25cb31
> > --- /dev/null
> > +++ b/drivers/hwmon/ltc2991.c
> > @@ -0,0 +1,479 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2023 Analog Devices, Inc.
> > + * Author: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > + */
> > +
> > +#include <linux/bitops.h>
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> > +#include <linux/i2c.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/property.h>
> > +#include <linux/regmap.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +#include <asm/unaligned.h>
> > +
> > +#define LTC2991_STATUS_LOW 0x00
> > +#define LTC2991_CH_EN_TRIGGER 0x01
> > +#define LTC2991_V1_V4_CTRL 0x06
> > +#define LTC2991_V5_V8_CTRL 0x07
> > +#define LTC2991_PWM_TH_LSB_T_INT 0x08
> > +#define LTC2991_PWM_TH_MSB 0x09
> > +#define LTC2991_CHANNEL_V_MSB(x) (0x0A + ((x) * 2))
> > +#define LTC2991_CHANNEL_T_MSB(x) (0x0A + ((x) * 4))
> > +#define LTC2991_CHANNEL_C_MSB(x) (0x0C + ((x) * 4))
> > +#define LTC2991_T_INT_MSB 0x1A
> > +#define LTC2991_VCC_MSB 0x1C
> > +
> > +#define LTC2991_V7_V8_EN BIT(7)
> > +#define LTC2991_V5_V6_EN BIT(6)
> > +#define LTC2991_V3_V4_EN BIT(5)
> > +#define LTC2991_V1_V2_EN BIT(4)
> > +#define LTC2991_T_INT_VCC_EN BIT(3)
> > +
> > +#define LTC2991_V3_V4_FILT_EN BIT(7)
> > +#define LTC2991_V3_V4_TEMP_EN BIT(5)
> > +#define LTC2991_V3_V4_DIFF_EN BIT(4)
> > +#define LTC2991_V1_V2_FILT_EN BIT(3)
> > +#define LTC2991_V1_V2_TEMP_EN BIT(1)
> > +#define LTC2991_V1_V2_DIFF_EN BIT(0)
> > +
> > +#define LTC2991_V7_V8_FILT_EN BIT(7)
> > +#define LTC2991_V7_V8_TEMP_EN BIT(5)
> > +#define LTC2991_V7_V8_DIFF_EN BIT(4)
> > +#define LTC2991_V5_V6_FILT_EN BIT(7)
> > +#define LTC2991_V5_V6_TEMP_EN BIT(5)
> > +#define LTC2991_V5_V6_DIFF_EN BIT(4)
> > +
> > +#define LTC2991_REPEAT_ACQ_EN BIT(4)
> > +#define LTC2991_T_INT_FILT_EN BIT(3)
> > +
> > +#define LTC2991_MAX_CHANNEL 4
> > +#define LTC2991_T_INT_CH_NR 4
> > +#define LTC2991_VCC_CH_NR 0
> > +
> > +static const char *const label_voltages[] = {
> > + "vcc",
> > + "voltage1",
> > + "voltage2",
> > + "voltage3",
> > + "voltage4",
> > + "voltage5",
> > + "voltage6",
> > + "voltage7",
> > + "voltage8"
> > +};
> > +
> > +static const char *const label_temp[] = {
> > + "t1",
> > + "t2",
> > + "t3",
> > + "t4",
> > + "t_int"
> > +};
> > +
> > +static const char *const label_curr[] = {
> > + "v1-v2",
> > + "v3-v4",
> > + "v5-v6",
> > + "v7-v8"
> > +};
> > +
> > +struct ltc2991_state {
> > + struct i2c_client *client;
> > + struct regmap *regmap;
> > + u32 r_sense_uohm[LTC2991_MAX_CHANNEL];
> > + bool temp_en[LTC2991_MAX_CHANNEL];
> > +};
> > +
> > +static int ltc2991_read_reg(struct ltc2991_state *st, u8 addr, u8 reg_len,
> > + int *val)
> > +{
> > + u8 regvals[2];
> > + int ret;
> > +
> > + if (reg_len > 2 || !reg_len)
> > + return -EINVAL;
> > +
>
> IMO, this is too much checking... It's an internal API, just make sure to
> properly call it ;).
>
> > + ret = regmap_bulk_read(st->regmap, addr, regvals, reg_len);
> > + if (ret)
> > + return ret;
> > +
> > + if (reg_len == 2)
> > + *val = get_unaligned_be16(®vals[0]);
> > + else
> > + *val = regvals[0];
>
> not what I had in mind. Having unaligned access is overkill when you can go with
> typical __be16 + __be16_to_cpu(). If I'm not missing anything, you just have to
> shift out the LSB in case of 1byte registers. Alternatively, before the bulk()
> call you can:
>
> if (reg_len < 2)
> return regmap_read();
>
> and then just assume 2 byte reads...
>
> > + return 0;
> > +}
> > +
> > +static int ltc2991_get_voltage(struct ltc2991_state *st, u32 reg, long *val)
> > +{
> > + int reg_val, ret, offset = 0;
> > +
> > + ret = ltc2991_read_reg(st, reg, 2, ®_val);
> > + if (ret)
> > + return ret;
> > +
> > + if (reg == LTC2991_VCC_MSB)
> > + /* Vcc 2.5V offset */
> > + offset = 2500;
> > +
> > + /* Vx, 305.18uV/LSB */
> > + *val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 30518,
> > + 1000 * 100) + offset;
> > +
> > + return 0;
> > +}
> > +
> > +static int ltc2991_read_in(struct device *dev, u32 attr, int channel, long
> > *val)
> > +{
> > + struct ltc2991_state *st = dev_get_drvdata(dev);
> > + u32 reg;
> > +
> > + switch (attr) {
> > + case hwmon_in_input:
> > + if (channel == LTC2991_VCC_CH_NR)
> > + reg = LTC2991_VCC_MSB;
> > + else
> > + reg = LTC2991_CHANNEL_V_MSB(channel - 1);
> > + break;
> > + default:
> > + return -EOPNOTSUPP;
> > + }
> > +
> > + return ltc2991_get_voltage(st, reg, val);
> > +}
> > +
> > +static int ltc2991_get_curr(struct ltc2991_state *st, u32 reg, int channel,
> > + long *val)
> > +{
> > + int reg_val, ret;
> > +
> > + ret = ltc2991_read_reg(st, reg, 2, ®_val);
> > + if (ret)
> > + return ret;
> > +
> > + /* Vx-Vy, 19.075uV/LSB */
> > + *val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 19075, 1000)
> > + / (st->r_sense_uohm[channel] / 1000);
> > +
> > + return 0;
> > +}
> > +
> > +static int ltc2991_read_curr(struct device *dev, u32 attr, int channel,
> > + long *val)
> > +{
> > + struct ltc2991_state *st = dev_get_drvdata(dev);
> > + u32 reg;
> > +
> > + switch (attr) {
> > + case hwmon_curr_input:
> > + reg = LTC2991_CHANNEL_C_MSB(channel);
> > + return ltc2991_get_curr(st, reg, channel, val);
> > + default:
> > + return -EOPNOTSUPP;
> > + }
> > +}
> > +
> > +static int ltc2991_get_temp(struct ltc2991_state *st, u32 reg, int channel,
> > + long *val)
> > +{
> > + int reg_val, ret;
> > +
> > + ret = ltc2991_read_reg(st, reg, 2, ®_val);
> > + if (ret)
> > + return ret;
> > +
> > + /* Temp LSB = 0.0625 Degrees */
> > + *val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 12) * 1000, 16);
> > +
> > + return 0;
> > +}
> > +
> > +static int ltc2991_read_temp(struct device *dev, u32 attr, int channel,
> > + long *val)
> > +{
> > + struct ltc2991_state *st = dev_get_drvdata(dev);
> > + u32 reg;
> > +
> > + switch (attr) {
> > + case hwmon_temp_input:
> > + if (channel == LTC2991_T_INT_CH_NR)
> > + reg = LTC2991_T_INT_MSB;
> > + else
> > + reg = LTC2991_CHANNEL_T_MSB(channel);
> > +
> > + return ltc2991_get_temp(st, reg, channel, val);
> > + default:
> > + return -EOPNOTSUPP;
> > + }
> > +}
> > +
> > +static int ltc2991_read(struct device *dev, enum hwmon_sensor_types type,
> > + u32 attr, int channel, long *val)
> > +{
> > + switch (type) {
> > + case hwmon_in:
> > + return ltc2991_read_in(dev, attr, channel, val);
> > + case hwmon_curr:
> > + return ltc2991_read_curr(dev, attr, channel, val);
> > + case hwmon_temp:
> > + return ltc2991_read_temp(dev, attr, channel, val);
> > + default:
> > + return -EOPNOTSUPP;
> > + }
> > +}
> > +
> > +static umode_t ltc2991_is_visible(const void *data,
> > + enum hwmon_sensor_types type, u32 attr,
> > + int channel)
> > +{
> > + const struct ltc2991_state *st = data;
> > +
> > + switch (type) {
> > + case hwmon_in:
> > + switch (attr) {
> > + case hwmon_in_input:
> > + case hwmon_in_label:
> > + return 0444;
> > + }
> > + break;
> > + case hwmon_curr:
> > + switch (attr) {
> > + case hwmon_curr_input:
> > + case hwmon_curr_label:
> > + if (st->r_sense_uohm[channel])
> > + return 0444;
> > + break;
> > + }
>
> This is what I was speaking about... You should go read again v1 an try to
> understand the points made or continue the discussion.
>
> I didn't looked at the datasheet but what I understood from Guenter is that each
> channel can only be a specific type of sensor and you should be explicit about
> that (not using rsense as the deciding factor). Thus, your bindings should
> likely be refactored so you have a property that explicitly "defines" a channel
> (not forgetting to handle things like differential channels and overlaps etc...)
> and then you need to reflect the ABI according to what sensors OF/ACPI have
> defined.
>
> This looks a bit like the ltc2983 [1] I upstreamed where most of the fun was in
> defining the channels (and maybe that one was actually an hwmon driver but what
> did I know back then :))
>
> Also important is that in absence of OF/ACPI, you should read whatever
> configuration is the device holding so, once again, you export the correct ABI.
> But in this case, I'm not really sure what would be a sane (if there's one) for
> rsense in case of a current sensor.
>
> Hopefully I got it right...
>
> > + break;
> > + case hwmon_temp:
> > + switch (attr) {
> > + case hwmon_temp_input:
> > + case hwmon_temp_label:
> > + if (st->temp_en[channel] ||
> > + channel == LTC2991_T_INT_CH_NR)
> > + return 0444;
> > + break;
> > + }
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int ltc2991_read_string(struct device *dev, enum hwmon_sensor_types
> > type,
> > + u32 attr, int channel, const char **str)
> > +{
> > + switch (type) {
> > + case hwmon_temp:
> > + *str = label_temp[channel];
> > + break;
> > + case hwmon_curr:
> > + *str = label_curr[channel];
> > + break;
> > + case hwmon_in:
> > + *str = label_voltages[channel];
> > + break;
> > + default:
> > + return -EOPNOTSUPP;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static const struct hwmon_ops ltc2991_hwmon_ops = {
> > + .is_visible = ltc2991_is_visible,
> > + .read = ltc2991_read,
> > + .read_string = ltc2991_read_string,
> > +};
> > +
> > +static const struct hwmon_channel_info *ltc2991_info[] = {
> > + HWMON_CHANNEL_INFO(temp,
> > + HWMON_T_INPUT | HWMON_T_LABEL,
> > + HWMON_T_INPUT | HWMON_T_LABEL,
> > + HWMON_T_INPUT | HWMON_T_LABEL,
> > + HWMON_T_INPUT | HWMON_T_LABEL,
> > + HWMON_T_INPUT | HWMON_T_LABEL
> > + ),
> > + HWMON_CHANNEL_INFO(curr,
> > + HWMON_C_INPUT | HWMON_C_LABEL,
> > + HWMON_C_INPUT | HWMON_C_LABEL,
> > + HWMON_C_INPUT | HWMON_C_LABEL,
> > + HWMON_C_INPUT | HWMON_C_LABEL
> > + ),
> > + HWMON_CHANNEL_INFO(in,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL,
> > + HWMON_I_INPUT | HWMON_I_LABEL
> > + ),
> > + NULL
> > +};
> > +
> > +static const struct hwmon_chip_info ltc2991_chip_info = {
> > + .ops = <c2991_hwmon_ops,
> > + .info = ltc2991_info,
> > +};
> > +
> > +static const struct regmap_config ltc2991_regmap_config = {
> > + .reg_bits = 8,
> > + .val_bits = 8,
> > + .max_register = 0x1D,
> > +};
> > +
> > +static int ltc2991_init(struct ltc2991_state *st)
> > +{
> > + struct fwnode_handle *child;
> > + int ret;
> > + u32 val, addr;
> > + u8 v5_v8_reg_data = 0, v1_v4_reg_data = 0;
> > +
> > + ret = devm_regulator_get_enable(&st->client->dev, "vcc");
> > + if (ret)
> > + return dev_err_probe(&st->client->dev, ret,
> > + "failed to enable regulator\n");
> > +
> > + device_for_each_child_node(&st->client->dev, child) {
> > + ret = fwnode_property_read_u32(child, "reg", &addr);
> > + if (ret < 0) {
> > + fwnode_handle_put(child);
> > + return ret;
> > + }
> > +
> > + if (addr > 3) {
> > + fwnode_handle_put(child);
> > + return -EINVAL;
> > + }
> > +
> > + ret = fwnode_property_read_u32(child, "shunt-resistor-micro-
> > ohms", &val);
> > + if (!ret) {
> > + st->r_sense_uohm[addr] = val;
>
> This still allows 0 as a valid value which would lead to a divide by 0
> exception...
>
> [1]: https://elixir.bootlin.com/linux/v6.6-rc5/source/drivers/iio/temperature/ltc2983.c#L1371
>
> - Nuno Sá
>
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