[PATCH v2 6/7] hwmon: Add Broadcom PMB PVTMON monitoring
Guenter Roeck
linux at roeck-us.net
Sun Nov 1 19:05:56 PST 2026
On 11/1/26 14:14, Linus Walleij wrote:
> Expose the BCM6846 die temperature and seven voltage inputs through
> hwmon using the shared Processor Monitor Bus (PMB) regmap.
>
> Register the temperature channel with the thermal framework so
> existing zero-cell device-tree thermal sensor references work.
>
> Poll for valid samples with a bounded timeout, releasing the PMB lock
> between reads. Report temperature in millidegrees Celsius, including
> negative values, and voltages in millivolts.
>
> Signed-off-by: Linus Walleij <linusw at kernel.org>
Acked-by: Guenter Roeck <linux at roeck-us.net>
Please let me know if you want me to take this patch through
the hwmon subsystem.
Thanks,
Guenter
> ---
> Documentation/hwmon/bcm_pmb_pvtmon.rst | 53 ++++++++
> Documentation/hwmon/index.rst | 1 +
> MAINTAINERS | 2 +
> drivers/hwmon/Kconfig | 18 +++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/bcm_pmb_pvtmon.c | 232 +++++++++++++++++++++++++++++++++
> 6 files changed, 307 insertions(+)
>
> diff --git a/Documentation/hwmon/bcm_pmb_pvtmon.rst b/Documentation/hwmon/bcm_pmb_pvtmon.rst
> new file mode 100644
> index 000000000000..7dba658bdc76
> --- /dev/null
> +++ b/Documentation/hwmon/bcm_pmb_pvtmon.rst
> @@ -0,0 +1,53 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +Kernel driver bcm_pmb_pvtmon
> +============================
> +
> +Supported chips:
> +
> + * Broadcom BCM6846 PVTMON
> +
> + Access: Processor Monitor Bus (PMB), bus 1, device 6
> +
> +Author: Linus Walleij <linusw at kernel.org>
> +
> +Description
> +-----------
> +
> +The process, voltage and temperature monitor (PVTMON) measures die
> +temperature and seven voltage inputs. The driver uses the shared PMB MFD
> +transport and obtains its clock and reset from the sibling providers.
> +
> +With CONFIG_THERMAL_OF enabled, the temperature channel also supplies
> +device-tree thermal zones. The PVTMON node uses #thermal-sensor-cells = <0>;
> +voltage inputs do not have thermal sensor indices.
> +
> +Sysfs attributes
> +----------------
> +
> +All attributes are read-only. Temperature is reported in millidegrees
> +Celsius and voltages in millivolts, using the BCM6846 vendor conversion
> +formulas and input-divider ratios.
> +
> +================ ================================
> +Attribute Description
> +================ ================================
> +temp1_input Die temperature
> +in0_input First 0.85 V input
> +in1_input Second 0.85 V input
> +in2_input VIN input
> +in3_input 1.0 V input
> +in4_input 1.8 V input
> +in5_input 3.3 V input
> +in6_input Diagnostic test input
> +in0_label V0.85_1
> +in1_label V0.85_2
> +in2_label VIN
> +in3_label V1.0
> +in4_label V1.8
> +in5_label V3.3
> +in6_label Vtest
> +================ ================================
> +
> +Labels follow the vendor channel names. Vtest is a diagnostic ADC input,
> +not a supply rail. The driver does not change the analog test routing.
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 199ca79621e9..5a579391cf9e 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -54,6 +54,7 @@ Hardware Monitoring Kernel Drivers
> axiado-pwm-fan
> axiado-tsadc
> bcm54140
> + bcm_pmb_pvtmon
> bel-pfe
> bpa-rs600
> cgbc-hwmon
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 74f0783d512f..124d67ea1582 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5451,7 +5451,9 @@ F: Documentation/devicetree/bindings/hwmon/brcm,bcm6846-pmb-pvtmon.yaml
> F: Documentation/devicetree/bindings/mfd/brcm,bcm6846-pmc.yaml
> F: Documentation/devicetree/bindings/reset/brcm,bcm6846-pmb-reset.yaml
> F: Documentation/devicetree/bindings/soc/bcm/brcm,bcm6846-pmb.yaml
> +F: Documentation/hwmon/bcm_pmb_pvtmon.rst
> F: drivers/clk/bcm/clk-bcmbca-pmb.c
> +F: drivers/hwmon/bcm_pmb_pvtmon.c
> F: drivers/mfd/bcmbca_pmc3_pmb.c
> F: drivers/reset/reset-bcmbca-pmb.c
> F: include/dt-bindings/clock/brcm,bcm6846-pmb.h
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 18c682e1a475..7e2bc32628d4 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -334,6 +334,24 @@ config SENSORS_AXIADO_TSADC
> This driver can also be built as a module. If so, the module
> will be called axiado-tsadc.
>
> +config SENSORS_BCM_PMB_PVTMON
> + tristate "Broadcom PMB PVTMON hardware monitoring"
> + depends on ARCH_BCMBCA || COMPILE_TEST
> + depends on MFD_BCMBCA_PMB
> + depends on COMMON_CLK
> + depends on RESET_CONTROLLER
> + select CLK_BCMBCA_PMB
> + select RESET_BCMBCA_PMB
> + select REGMAP
> + default MFD_BCMBCA_PMB
> + help
> + Enable temperature and voltage monitoring through the Processor
> + Monitor Bus on Broadcom BCM6846. With THERMAL_OF enabled, the
> + temperature channel also supplies the thermal zones described in
> + the device tree.
> +
> + This driver can also be built as a module called bcm_pmb_pvtmon.
> +
> config SENSORS_K8TEMP
> tristate "AMD Athlon64/FX or Opteron temperature sensor"
> depends on X86 && PCI
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index d4c345ed7261..edf8e8d2f345 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_SENSORS_ATXP1) += atxp1.o
> obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
> obj-$(CONFIG_SENSORS_AXIADO_PWM_FAN) += axiado-pwm-fan.o
> obj-$(CONFIG_SENSORS_AXIADO_TSADC) += axiado-tsadc.o
> +obj-$(CONFIG_SENSORS_BCM_PMB_PVTMON) += bcm_pmb_pvtmon.o
> obj-$(CONFIG_SENSORS_CGBC) += cgbc-hwmon.o
> obj-$(CONFIG_SENSORS_CHIPCAP2) += chipcap2.o
> obj-$(CONFIG_SENSORS_CORETEMP) += coretemp.o
> diff --git a/drivers/hwmon/bcm_pmb_pvtmon.c b/drivers/hwmon/bcm_pmb_pvtmon.c
> new file mode 100644
> index 000000000000..8b95dac83994
> --- /dev/null
> +++ b/drivers/hwmon/bcm_pmb_pvtmon.c
> @@ -0,0 +1,232 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Broadcom BCM6846 process, voltage and temperature monitor (PVTMON).
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/hwmon.h>
> +#include <linux/mfd/bcmbca-pmb.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +
> +#define PVTMON_BUS 1
> +#define PVTMON_DEVICE 6
> +
> +/* PMB register offsets are in 32-bit words. */
> +#define PVTMON_CONFIG 17
> +#define PVTMON_RESET_N BIT(0)
> +#define PVTMON_POWER_DOWN BIT(1)
> +
> +#define PVTMON_ACQ_CONFIG 20
> +#define PVTMON_ACCUM_ENABLE BIT(0)
> +#define PVTMON_SKIP_LENGTH GENMASK(11, 8)
> +
> +#define PVTMON_CHANNEL_BASE 24
> +#define PVTMON_NUM_CHANNELS 8
> +#define PVTMON_VALUE GENMASK(9, 0)
> +#define PVTMON_VALID BIT(18)
> +#define PVTMON_SAMPLES GENMASK(26, 24)
> +#define PVTMON_CHANNEL_ENABLE BIT(31)
> +
> +/* Voltage labels and divider ratios follow the BCM6846 vendor definitions. */
> +static const struct {
> + const char *label;
> + unsigned int divisor;
> +} bcm6846_pvtmon_voltages[] = {
> + { "V0.85_1", 10 },
> + { "V0.85_2", 10 },
> + { "VIN", 7 },
> + { "V1.0", 7 },
> + { "V1.8", 4 },
> + { "V3.3", 2 },
> + { "Vtest", 10 },
> +};
> +
> +static int bcm_pmb_pvtmon_init(struct regmap *regmap,
> + struct reset_control *reset)
> +{
> + unsigned int reg = BCMBCA_PMB_REG(PVTMON_BUS, PVTMON_DEVICE, PVTMON_CONFIG);
> + u32 config, acq, channel;
> + unsigned int i;
> + int ret;
> +
> + ret = regmap_read(regmap, reg, &config);
> + if (ret)
> + return ret;
> +
> + /* Do not reset acquisition already running for the PMC firmware. */
> + if ((config & (PVTMON_RESET_N | PVTMON_POWER_DOWN)) != PVTMON_RESET_N) {
> + ret = regmap_update_bits(regmap, reg, PVTMON_POWER_DOWN, 0);
> + if (ret)
> + return ret;
> + ret = reset_control_reset(reset);
> + if (ret)
> + return ret;
> + }
> +
> + ret = regmap_read(regmap, BCMBCA_PMB_REG(PVTMON_BUS, PVTMON_DEVICE,
> + PVTMON_ACQ_CONFIG), &acq);
> + if (ret)
> + return ret;
> +
> + for (i = 0; i < PVTMON_NUM_CHANNELS; i++) {
> + reg = BCMBCA_PMB_REG(PVTMON_BUS, PVTMON_DEVICE, PVTMON_CHANNEL_BASE + i);
> + ret = regmap_read(regmap, reg, &channel);
> + if (ret)
> + return ret;
> +
> + if (channel & PVTMON_CHANNEL_ENABLE)
> + continue;
> +
> + /* Average 32 samples, matching the vendor acquisition setup. */
> + ret = regmap_update_bits(regmap, reg, PVTMON_CHANNEL_ENABLE | PVTMON_SAMPLES,
> + PVTMON_CHANNEL_ENABLE | FIELD_PREP(PVTMON_SAMPLES, 5));
> + if (ret)
> + return ret;
> + }
> +
> + if (!(acq & PVTMON_ACCUM_ENABLE))
> + return regmap_update_bits(regmap,
> + BCMBCA_PMB_REG(PVTMON_BUS, PVTMON_DEVICE,
> + PVTMON_ACQ_CONFIG),
> + PVTMON_SKIP_LENGTH | PVTMON_ACCUM_ENABLE,
> + PVTMON_ACCUM_ENABLE | FIELD_PREP(PVTMON_SKIP_LENGTH, 8));
> +
> + return 0;
> +}
> +
> +static int bcm_pmb_pvtmon_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + struct regmap *map = dev_get_drvdata(dev);
> + unsigned int index;
> + u32 value;
> + int ret;
> +
> + switch (type) {
> + case hwmon_temp:
> + if (attr != hwmon_temp_input)
> + return -EOPNOTSUPP;
> + index = 0;
> + break;
> + case hwmon_in:
> + if (attr != hwmon_in_input)
> + return -EOPNOTSUPP;
> + index = channel + 1;
> + break;
> + default:
> + return -EOPNOTSUPP;
> + }
> +
> + /* Release the PMB between samples so other clients can make progress. */
> + ret = regmap_read_poll_timeout(map,
> + BCMBCA_PMB_REG(PVTMON_BUS, PVTMON_DEVICE,
> + PVTMON_CHANNEL_BASE + index),
> + value, value & PVTMON_VALID, 1000, 100000);
> + if (ret)
> + return ret;
> +
> + value = FIELD_GET(PVTMON_VALUE, value);
> + if (type == hwmon_temp) {
> + /* Signed arithmetic allows temperatures below zero Celsius. */
> + *val = (41335000 - 49055 * (int)value) / 100;
> + } else {
> + /* 880 mV ADC reference, accounting for each input divider. */
> + *val = 880 * value * 10 /
> + (bcm6846_pvtmon_voltages[channel].divisor * 1024);
> + }
> +
> + return 0;
> +}
> +
> +static int bcm_pmb_pvtmon_read_string(struct device *dev,
> + enum hwmon_sensor_types type, u32 attr,
> + int channel, const char **str)
> +{
> + if (type != hwmon_in || attr != hwmon_in_label)
> + return -EOPNOTSUPP;
> +
> + *str = bcm6846_pvtmon_voltages[channel].label;
> + return 0;
> +}
> +
> +static const struct hwmon_ops bcm_pmb_pvtmon_ops = {
> + .visible = 0444,
> + .read = bcm_pmb_pvtmon_read,
> + .read_string = bcm_pmb_pvtmon_read_string,
> +};
> +
> +static const struct hwmon_channel_info * const bcm_pmb_pvtmon_info[] = {
> + HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
> + HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
> + 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),
> + NULL
> +};
> +
> +static const struct hwmon_chip_info bcm_pmb_pvtmon_chip_info = {
> + .ops = &bcm_pmb_pvtmon_ops,
> + .info = bcm_pmb_pvtmon_info,
> +};
> +
> +static int bcm_pmb_pvtmon_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct regmap *regmap = dev_get_regmap(dev->parent, NULL);
> + struct device *hwmon;
> + struct reset_control *reset;
> + struct clk *clk;
> + int ret;
> +
> + if (!regmap)
> + return -ENODEV;
> +
> + reset = devm_reset_control_get_exclusive(dev, NULL);
> + if (IS_ERR(reset))
> + return dev_err_probe(dev, PTR_ERR(reset), "failed to get PVTMON reset\n");
> +
> + clk = devm_clk_get_enabled(dev, NULL);
> + if (IS_ERR(clk))
> + return dev_err_probe(dev, PTR_ERR(clk), "failed to enable PVTMON clock\n");
> +
> + ret = bcm_pmb_pvtmon_init(regmap, reset);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to initialize PVTMON\n");
> +
> + hwmon = devm_hwmon_device_register_with_info(dev, "bcm6846_pvtmon", regmap,
> + &bcm_pmb_pvtmon_chip_info, NULL);
> + if (IS_ERR(hwmon))
> + return dev_err_probe(dev, PTR_ERR(hwmon), "failed to register hwmon device\n");
> +
> + /* Acquisition remains enabled for the PMC firmware after unbinding. */
> + return 0;
> +}
> +
> +static const struct of_device_id bcm_pmb_pvtmon_of_match[] = {
> + { .compatible = "brcm,bcm6846-pmb-pvtmon" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, bcm_pmb_pvtmon_of_match);
> +
> +static struct platform_driver bcm_pmb_pvtmon_driver = {
> + .probe = bcm_pmb_pvtmon_probe,
> + .driver = {
> + .name = "bcm6846-pmb-pvtmon",
> + .of_match_table = bcm_pmb_pvtmon_of_match,
> + },
> +};
> +module_platform_driver(bcm_pmb_pvtmon_driver);
> +
> +MODULE_AUTHOR("Linus Walleij <linusw at kernel.org>");
> +MODULE_DESCRIPTION("Broadcom PMB PVTMON hardware monitoring driver");
> +MODULE_LICENSE("GPL");
>
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