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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Fri, 15 Sep 2023 09:24:49 -0700
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To:     David Ober <dober6023@gmail.com>, linux-hwmon@vger.kernel.org
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        jdelvare@suse.com, corbet@lwn.net, dober@lenovo.com,
        mpearson@lenovo.com
References: <20230915150340.301067-1-dober6023@gmail.com>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] hwmon:Add MEC172x Micro Chip driver for Lenovo
 motherboards
In-Reply-To: <20230915150340.301067-1-dober6023@gmail.com>
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On 9/15/23 08:03, David Ober wrote:
> This addition adds in the ability for the system to scan the
> MEC172x EC chip in Lenovo ThinkStation systems to get the
> current fan RPM speeds and the Maximum speed value for each
> fan also provides the current CPU and DIMM thermal status
> 
> Signed-off-by: David Ober <dober6023@gmail.com>
> 
> Written by David Ober from Lenovo using this gmail address since
> my corporate email address does not comply with git email
> ---
>   drivers/hwmon/Kconfig             |  10 +
>   drivers/hwmon/Makefile            |   1 +
>   drivers/hwmon/lenovo-ec-sensors.c | 471 ++++++++++++++++++++++++++++++
>   3 files changed, 482 insertions(+)
>   create mode 100644 drivers/hwmon/lenovo-ec-sensors.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 307477b8a371..565fc957a900 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -852,6 +852,16 @@ config SENSORS_LAN966X
>   	  This driver can also be built as a module. If so, the module
>   	  will be called lan966x-hwmon.
>   
> +config SENSORS_LENOVO_EC
> +        tristate "Microchip MEC172X Chip for Lenovo ThinkStation"
> +        depends on I2C
> +        help
> +          If you say yes here you get support for LENOVO
> +          EC Sensors on newer ThinkStation systems
> +
> +          This driver can also be built as a module. If so, the module
> +          will be called lenovo_ec_sensors.
> +
>   config SENSORS_LINEAGE
>   	tristate "Lineage Compact Power Line Power Entry Module"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 3f4b0fda0998..ac7855b48bd5 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -103,6 +103,7 @@ obj-$(CONFIG_SENSORS_JC42)	+= jc42.o
>   obj-$(CONFIG_SENSORS_K8TEMP)	+= k8temp.o
>   obj-$(CONFIG_SENSORS_K10TEMP)	+= k10temp.o
>   obj-$(CONFIG_SENSORS_LAN966X)	+= lan966x-hwmon.o
> +obj-$(CONFIG_SENSORS_LENOVO_EC)	+= lenovo-ec-sensors.o
>   obj-$(CONFIG_SENSORS_LINEAGE)	+= lineage-pem.o
>   obj-$(CONFIG_SENSORS_LOCHNAGAR)	+= lochnagar-hwmon.o
>   obj-$(CONFIG_SENSORS_LM63)	+= lm63.o
> diff --git a/drivers/hwmon/lenovo-ec-sensors.c b/drivers/hwmon/lenovo-ec-sensors.c
> new file mode 100644
> index 000000000000..acf26ed4c96b
> --- /dev/null
> +++ b/drivers/hwmon/lenovo-ec-sensors.c
> @@ -0,0 +1,471 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * HWMON driver for MEC172x chip that publishes some sensor values
> + * via the embedded controller registers specific to Lenovo Systems.
> + *
> + * Copyright (C) 2023 David Ober (Lenovo) <dober@lenovo.com>
> + *
> + * EC provides:
> + * - CPU temperature
> + * - DIMM temperature
> + * - Chassis zone temperatures
> + * - CPU fan RPM
> + * - DIMM fan RPM
> + * - Chassis fans RPM
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/delay.h>
> +#include <linux/hwmon.h>
> +#include <linux/ioport.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/units.h>
> +
> +#define MCHP_SING_IDX			0x0000
> +#define MCHP_EMI0_APPLICATION_ID	0x090C
> +#define MCHP_EMI0_EC_ADDRESS_LSB	0x0902
> +#define MCHP_EMI0_EC_ADDRESS_MSB	0x0903
> +#define MCHP_EMI0_EC_DATA_BYTE0		0x0904
> +#define MCHP_EMI0_EC_DATA_BYTE1		0x0905
> +#define MCHP_EMI0_EC_DATA_BYTE2		0x0906
> +#define MCHP_EMI0_EC_DATA_BYTE3		0x0907
> +
> +#define IoWrite8(a, b)	outb_p(b, a)
> +#define IoRead8(a)	inb_p(a)
> +

Neither checkpatch nor me like CamelCase, so please avoid.

> +static inline uint8_t
> +get_ec_reg(unsigned char page, unsigned char index)
> +{
> +	u8 onebyte;
> +	unsigned short m_index;
> +	unsigned short phy_index = page * 256 + index;
> +
> +	if (IoRead8(MCHP_EMI0_APPLICATION_ID) != 0) /* EMI access locked */
> +		return false;

return false from a function returning get_ec_reg() ?

> +
> +	IoWrite8(MCHP_EMI0_APPLICATION_ID, 0x01);

What is a second process does exactly the same at the same time,
both reading 0 and writing 1 ? How would those two processes be
protected agaionst stepping each other on the foot ? And why
would it be an error if another process is currently accessing
the EC ?

In other words, why is there no locking ?

> +
> +	m_index = phy_index & 0x7FFC;
> +	IoWrite8(MCHP_EMI0_EC_ADDRESS_LSB, m_index);
> +	IoWrite8(MCHP_EMI0_EC_ADDRESS_MSB, m_index >> 8);
> +
> +	switch (phy_index & 0x0003) {
> +	case 0:
> +		onebyte = IoRead8(MCHP_EMI0_EC_DATA_BYTE0);
> +		break;
> +	case 1:
> +		onebyte = IoRead8(MCHP_EMI0_EC_DATA_BYTE1);
> +		break;
> +	case 2:
> +		onebyte = IoRead8(MCHP_EMI0_EC_DATA_BYTE2);
> +		break;
> +	case 3:
> +		onebyte = IoRead8(MCHP_EMI0_EC_DATA_BYTE3);
> +		break;
> +	}
> +
> +	IoWrite8(MCHP_EMI0_APPLICATION_ID, 0x01);  /* write same data to clean */

"same data" would be "onebyte", not 1. I assume you refer to the
similar write to MCHP_EMI0_APPLICATION_ID above. If so,
say so.

> +	return onebyte;

This is equivalent to the "error" return above. What if the EC does return 0 ?

> +}
> +
> +static const char * const systems[] = {
> +	"Tomcat",
> +	"Hornet",
> +	"Falcon",
> +	"Manta_",
> +};
> +
> +static const char * const lenovo_px_ec_temp_label[] = {
> +	"CPU1",
> +	"CPU2",
> +	"R_DIMM1",
> +	"L_DIMM1",
> +	"R_DIMM2",
> +	"L_DIMM2",
> +	"PCH",
> +	"M2_R",
> +	"M2_Z1R",
> +	"M2_Z2R",
> +	"PCI_Z1",
> +	"PCI_Z2",
> +	"PCI_Z3",
> +	"PCI_Z4",
> +	"AMB",
> +};
> +
> +static const char * const lenovo_gen_ec_temp_label[] = {
> +	"CPU1",
> +	"",
> +	"R_DIMM",
> +	"L_DIMM",
> +	"",
> +	"",
> +	"PCH",
> +	"M2_R",
> +	"M2_Z1R",
> +	"M2_Z2R",
> +	"PCI_Z1",
> +	"PCI_Z2",
> +	"PCI_Z3",
> +	"PCI_Z4",
> +	"AMB",
> +};
> +
> +static const char * const px_ec_fan_label[] = {
> +	"CPU1_Fan",
> +	"CPU2_Fan",
> +	"Front_Fan1-1",
> +	"Front_Fan1-2",
> +	"Front_Fan2",
> +	"Front_Fan3",
> +	"MEM_Fan1",
> +	"MEM_Fan2",
> +	"Rear_Fan1",
> +	"Rear_Fan2",
> +	"Flex_Bay_Fan1",
> +	"Flex_Bay_Fan2",
> +	"Flex_Bay_Fan2",
> +	"PSU_HDD_Fan",
> +	"PSU1_Fan",
> +	"PSU2_Fan",
> +};
> +
> +static const char * const p7_ec_fan_label[] = {
> +	"CPU1_Fan",
> +	"",
> +	"HP_CPU_Fan1",
> +	"HP_CPU_Fan2",
> +	"PCIE1_4_Fan",
> +	"PCIE5_7_Fan",
> +	"MEM_Fan1",
> +	"MEM_Fan2",
> +	"Rear_Fan1",
> +	"",
> +	"BCB_Fan",
> +	"Flex_Bay_Fan",
> +	"",
> +	"",
> +	"PSU_Fan",
> +	"",
> +};
> +
> +static const char * const p5_ec_fan_label[] = {
> +	"CPU_Fan",
> +	"",
> +	"",
> +	"",
> +	"",
> +	"HDD_Fan",
> +	"Duct_Fan1",
> +	"MEM_Fan",
> +	"Rear_Fan",
> +	"",
> +	"Front_Fan",
> +	"Flex_Bay_Fan",
> +	"",
> +	"",
> +	"PSU_Fan",
> +	"",
> +};
> +
> +static const char * const p7_amd_ec_fan_label[] = {
> +	"CPU1_Fan",
> +	"CPU2_Fan",
> +	"HP_CPU_Fan1",
> +	"HP_CPU_Fan2",
> +	"PCIE1_4_Fan",
> +	"PCIE5_7_Fan",
> +	"DIMM1_Fan1",
> +	"DIMM1_Fan2",
> +	"DIMM2_Fan1",
> +	"DIMM2_Fan2",
> +	"Rear_Fan",
> +	"HDD_Bay_Fan",
> +	"Flex_Bay_Fan",
> +	"",
> +	"PSU_Fan",
> +	"",
> +};
> +
> +struct ec_sensors_data {
> +	u8 platform_id;
> +	const char *const *fan_labels;
> +	const char *const *temp_labels;
> +};
> +
> +static int
> +lenovo_ec_do_read_temp(u32 attr, int channel, long *val)
> +{
> +	u8   LSB;
> +
> +	switch (attr) {
> +	case hwmon_temp_input:
> +		LSB = get_ec_reg(2, 0x81 + channel);
> +		if (LSB > 0x40) {
> +			*val = (LSB - 0x40) * 1000;
> +		} else {
> +			*val = 0;
> +			return -1;
> +		}
> +		return 0;
> +	default:
> +		break;
> +	}
> +	return -EOPNOTSUPP;
> +}
> +
> +static int
> +lenovo_ec_do_read_fan(u32 attr, int channel, long *val)
> +{
> +	u8    LSB, MSB;
> +
> +	channel *= 2;
> +	switch (attr) {
> +	case hwmon_fan_input:
> +		LSB = get_ec_reg(4, 0x60 + channel);
> +		MSB = get_ec_reg(4, 0x61 + channel);
> +		if ((MSB << 8) + LSB != 0) {
> +			LSB = get_ec_reg(4, 0x20 + channel);
> +			MSB = get_ec_reg(4, 0x21 + channel);
> +			*val = (MSB << 8) + LSB;
> +			return 0;
> +		}
> +		return -1;

What is the rationale for returning -EPERM on error, here and elsewhere ?

Either case, error handling should come first.

> +	case hwmon_fan_max:
> +		LSB = get_ec_reg(4, 0x60 + channel);
> +		MSB = get_ec_reg(4, 0x61 + channel);
> +		if ((MSB << 8) + LSB != 0) {
> +			LSB = get_ec_reg(4, 0x40 + channel);
> +			MSB = get_ec_reg(4, 0x41 + channel);
> +			*val = (MSB << 8) + LSB;
> +		} else {
> +			*val = 0;
> +		}

Hard to follow why other errors result in returning an error but not here.

> +		return 0;
> +	case hwmon_fan_min:
> +	case hwmon_fan_div:
> +	case hwmon_fan_alarm:
> +		break;
> +	default:
> +		break;
> +	}
> +	return -EOPNOTSUPP;
> +}
> +
> +static int get_platform(void)
> +{
> +	char system_type[6];
> +	int ret = -1;
> +	int idx;
> +
> +	for (idx = 0 ; idx < 6 ; idx++)
> +		system_type[idx] = get_ec_reg(0xC, (0x10 + idx));
> +
> +	for (idx = 0 ; idx < 4 ; idx++) {
> +		if (strcmp(systems[idx], system_type) == 0) {
> +			ret = idx;
> +			break;
> +		}
> +	}
> +	return ret;
> +}
> +
> +static int
> +lenovo_ec_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
> +			    u32 attr, int channel, const char **str)
> +{
> +	struct ec_sensors_data *state = dev_get_drvdata(dev);
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		*str = state->temp_labels[channel];
> +		break;
> +
> +	case hwmon_fan:
> +		*str = state->fan_labels[channel];
> +		break;
> +	default:
> +		return -EOPNOTSUPP; /* unreachable */
> +	}
> +	return 0;
> +}
> +
> +static int
> +lenovo_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> +		     u32 attr, int channel, long *val)
> +{
> +	switch (type) {
> +	case hwmon_temp:
> +		return lenovo_ec_do_read_temp(attr, channel, val);
> +	case hwmon_fan:
> +		return lenovo_ec_do_read_fan(attr, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static umode_t
> +lenovo_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_types type,
> +			   u32 attr, int channel)
> +{
> +	//if (type != hwmon_fan)
> +//		return 0;
> +

Seriously ?

> +	switch (type) {
> +	case hwmon_temp:
> +		if (attr == hwmon_temp_input || attr == hwmon_temp_label)
> +			return 0444;
> +		break;
> +	case hwmon_fan:
> +		if (attr == hwmon_fan_input || attr == hwmon_fan_max || attr == hwmon_fan_label)
> +			return 0444;
> +		break;
> +	default:
> +		return 0;
> +	}
> +	return 0;
> +}
> +
> +static const struct hwmon_channel_info *lenovo_ec_hwmon_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_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_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(fan,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX,
> +			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MAX),
> +	NULL
> +};
> +
> +static const struct hwmon_ops lenovo_ec_hwmon_ops = {
> +	.is_visible = lenovo_ec_hwmon_is_visible,
> +	.read = lenovo_ec_hwmon_read,
> +	.read_string = lenovo_ec_hwmon_read_string,
> +};
> +
> +static struct hwmon_chip_info lenovo_ec_chip_info = {
> +	.ops = &lenovo_ec_hwmon_ops,
> +	.info = lenovo_ec_hwmon_info,
> +};
> +
> +static int lenovo_ec_probe(struct platform_device *pdev)
> +{
> +	struct device *hwdev;
> +	struct ec_sensors_data *ec_data;
> +	const struct hwmon_chip_info *chip_info;
> +	struct device *dev = &pdev->dev;
> +
> +	ec_data = devm_kzalloc(dev, sizeof(struct ec_sensors_data), GFP_KERNEL);
> +	if (!ec_data)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, ec_data);
> +
> +	chip_info = &lenovo_ec_chip_info;
> +
> +	if (IoRead8(0x90C) != 0) {               /* check EMI Application BIT */
> +		IoWrite8(0x90C, IoRead8(0x90C)); /* set EMI Application BIT to 0 */
> +	}
> +	IoWrite8(MCHP_EMI0_EC_ADDRESS_LSB, MCHP_SING_IDX);
> +	IoWrite8(MCHP_EMI0_EC_ADDRESS_MSB, MCHP_SING_IDX >> 8);
> +
> +	if ((IoRead8(MCHP_EMI0_EC_DATA_BYTE0) == 'M') &&
> +	    (IoRead8(MCHP_EMI0_EC_DATA_BYTE1) == 'C') &&
> +	    (IoRead8(MCHP_EMI0_EC_DATA_BYTE2) == 'H') &&
> +	    (IoRead8(MCHP_EMI0_EC_DATA_BYTE3) == 'P')) {
> +		ec_data->platform_id = get_platform();
> +		switch (ec_data->platform_id) {
> +		case 0:
> +			ec_data->fan_labels = px_ec_fan_label;
> +			ec_data->temp_labels = lenovo_px_ec_temp_label;
> +			break;
> +		case 1:
> +			ec_data->fan_labels = p7_ec_fan_label;
> +			ec_data->temp_labels = lenovo_gen_ec_temp_label;
> +			break;
> +		case 2:
> +			ec_data->fan_labels = p5_ec_fan_label;
> +			ec_data->temp_labels = lenovo_gen_ec_temp_label;
> +			break;
> +		case 3:
> +			ec_data->fan_labels = p7_amd_ec_fan_label;
> +			ec_data->temp_labels = lenovo_gen_ec_temp_label;
> +			break;
> +		default:
> +			dev_err(dev, "Unknown ThinkStation Model");
> +			return -EINVAL;
> +		}
> +
> +		hwdev = devm_hwmon_device_register_with_info(dev, "lenovo_ec",
> +							     ec_data,
> +							     chip_info, NULL);
> +
> +		return PTR_ERR_OR_ZERO(hwdev);
> +	} else {
> +		return -ENODEV;

else after return is unnecessary, and error handling should come first.


	if (no match)
		return -ENODEV;

	registration code;

> +	}
> +}
> +
> +static struct platform_driver lenovo_ec_sensors_platform_driver = {
> +	.driver = {
> +		.name	= "lenovo-ec-sensors",
> +	},
> +	.probe = lenovo_ec_probe,
> +};
> +
> +static struct platform_device *lenovo_ec_sensors_platform_device;
> +
> +static int __init lenovo_ec_init(void)
> +{
> +	lenovo_ec_sensors_platform_device =
> +		platform_create_bundle(&lenovo_ec_sensors_platform_driver,
> +				       lenovo_ec_probe, NULL, 0, NULL, 0);
> +
> +	if (IS_ERR(lenovo_ec_sensors_platform_device))
> +		return PTR_ERR(lenovo_ec_sensors_platform_device);
> +
> +	return 0;

	return PTR_ERR_OR_ZERO() might do the same.

but then I don't entirely understand why you don't use
module_platform_driver().

Anyway, I am not really happy that the probe function is executed
on all systems, without checking if the EC exists, and pretty much
starts with writing into an IO address. How do you guarantee that
this doesn't mess up other systems ?

Guenter

> +}
> +
> +static void __exit lenovo_ec_exit(void)
> +{
> +	platform_device_unregister(lenovo_ec_sensors_platform_device);
> +	platform_driver_unregister(&lenovo_ec_sensors_platform_driver);
> +}
> +
> +module_init(lenovo_ec_init);
> +module_exit(lenovo_ec_exit);
> +
> +MODULE_AUTHOR("David Ober <dober@lenovo.com>");
> +MODULE_DESCRIPTION("HWMON driver for MEC172x EC sensors accessible via ACPI on LENOVO motherboards");
> +MODULE_LICENSE("GPL");