RE: [PATCH 1/3] hwmon: sbrmi: Add support for sbrmi power module

Chatradhi, Naveen Krishna
2021-06-29T15:05:59Z

[AMD Official Use Only]

Hi Guenter,

-----Original Message-----
From: Guenter Roeck <groeck7@gmail.com> On Behalf Of Guenter Roeck
Sent: Monday, June 28, 2021 8:29 PM
To: Chatradhi, Naveen Krishna <NaveenKrishna.Chatradhi@amd.com>; linux-hwmon@vger.kernel.org
Cc: Gupta, Akshay <Akshay.Gupta@amd.com>
Subject: Re: [PATCH 1/3] hwmon: sbrmi: Add support for sbrmi power module

[CAUTION: External Email]

On 6/25/21 6:25 AM, Naveen Krishna Chatradhi wrote:
> From: Akshay Gupta <Akshay.Gupta@amd.com>
>
> On AMD platforms the Out-of-band access is provided by Advanced
> Platform Management

This is a bit too long for checkpatch.

> Link (APML), APML is a SMBus v2.0 compatible 2-wire processor client interface.
> APML is also referred as the sideband interface (SBI).
>
> APML is used to communicate with the Remote Management Interface
> (SB-Remote Management Interface (SB-RMI) which provides Soft Mailbox
> messages to report power consumption and power limits of the CPU socket.
>
> - This module add support to read power consumption,
> power limit & max power limit and write power limit.
> - To instantiate this driver on an AMD CPU with SB-RMI support,
> the i2c bus number would be the bus connected from the board
> management controller (BMC) to the CPU.
>

This is a bit vague. Would this driver be instantiated on the host CPU or on the BMC ?

> Signed-off-by: Akshay Gupta <Akshay.Gupta@amd.com>
> Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
> ---
> drivers/hwmon/Kconfig | 10 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/sbrmi.c | 394 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 405 insertions(+)
> create mode 100644 drivers/hwmon/sbrmi.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig index
> 87624902ea80..d1813ea8382c 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1551,6 +1551,16 @@ config SENSORS_SBTSI
> This driver can also be built as a module. If so, the module will
> be called sbtsi_temp.
>
> +config SENSORS_SBRMI
> + tristate "Emulated SB-RMI sensor"
> + depends on I2C
> + help
> + If you say yes here you get support for emulated RMI
> + sensors on AMD SoCs with APML interface connected to a BMC device.
> +
> + This driver can also be built as a module. If so, the module will
> + be called sbrmi.
> +
> config SENSORS_SHT15
> tristate "Sensiron humidity and temperature sensors. SHT15 and compat."
> depends on GPIOLIB || COMPILE_TEST diff --git
> a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile index
> 59e78bc212cf..8031acf58936 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -164,6 +164,7 @@ obj-$(CONFIG_SENSORS_PWM_FAN) += pwm-fan.o
> obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON) += raspberrypi-hwmon.o
> obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o
> obj-$(CONFIG_SENSORS_SBTSI) += sbtsi_temp.o
> +obj-$(CONFIG_SENSORS_SBRMI) += sbrmi.o
> obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
> obj-$(CONFIG_SENSORS_SCH5627) += sch5627.o
> obj-$(CONFIG_SENSORS_SCH5636) += sch5636.o
> diff --git a/drivers/hwmon/sbrmi.c b/drivers/hwmon/sbrmi.c new file
> mode 100644 index 000000000000..c35829513459
> --- /dev/null
> +++ b/drivers/hwmon/sbrmi.c
> @@ -0,0 +1,394 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * sbrmi.c - hwmon driver for a SB-RMI mailbox
> + * compliant AMD SoC device.
> + *
> + * Copyright (C) 2020-2021 Advanced Micro Devices, Inc.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>

I don't immediately see why this include is needed.

> +#include <asm-generic/ioctl.h>

This looks wrong, and I don't immediately see why it would be needed.

> +#include <linux/delay.h>

Alphabetic include file order, please.

> +
> +/* Do not allow setting negative power limit */ #define SBRMI_PWR_MIN
> +0
> +/* Mask for Status Register bit[1] */ #define SW_ALERT_MASK 0x2
> +

Please always use

#define<space>DEFINITION<tab>value
^^^^^

> +/* Software Interrupt for triggering */
> +#define START_CMD 0x80
> +#define TRIGGER_MAILBOX 0x01
> +
> +/*
> + * SB-RMI supports soft mailbox service request to MP1 (power
> +management
> + * firmware) through SBRMI inbound/outbound message registers.
> + * SB-RMI message IDs
> + */
> +enum sbrmi_msg_id {
> + SBRMI_READ_PKG_PWR_CONSUMPTION = 0x1,
> + SBRMI_WRITE_PKG_PWR_LIMIT,
> + SBRMI_READ_PKG_PWR_LIMIT,
> + SBRMI_READ_PKG_MAX_PWR_LIMIT,
> +};
> +
> +/* SB-RMI registers */
> +enum sbrmi_reg {
> + SBRMI_CTRL = 0x01,
> + SBRMI_STATUS,
> + SBRMI_OUTBNDMSG0 = 0x30,
> + SBRMI_OUTBNDMSG1,
> + SBRMI_OUTBNDMSG2,
> + SBRMI_OUTBNDMSG3,
> + SBRMI_OUTBNDMSG4,
> + SBRMI_OUTBNDMSG5,
> + SBRMI_OUTBNDMSG6,
> + SBRMI_OUTBNDMSG7,
> + SBRMI_INBNDMSG0,
> + SBRMI_INBNDMSG1,
> + SBRMI_INBNDMSG2,
> + SBRMI_INBNDMSG3,
> + SBRMI_INBNDMSG4,
> + SBRMI_INBNDMSG5,
> + SBRMI_INBNDMSG6,
> + SBRMI_INBNDMSG7,
> + SBRMI_SW_INTERRUPT,
> +};
> +
> +/*
> + * Each client has this additional data */

Please be consistent with comments: This does not really need to be a multi-line comment. While that does not really matter, you use a single-line comment to describe the next structure. Please make it both either single-line or multi-line.

> +struct sbrmi_data {
> + struct i2c_client *client;
> + struct mutex lock;
> +};
> +
> +/* Mailbox message data format */
> +union mailbox_word {
> + u8 bytes[4];
> + u32 value;

That strongly suggests that the driver will only work on either little-endian or big-endian systems, depending on the byte order of transfers. Please restrict it accordingly.

> +};
> +
> +struct sbrmi_mailbox_msg {
> + u8 cmd;
> + bool read;
> + union mailbox_word data_in;
> + union mailbox_word data_out;
> +};
> +
> +static int print_mailbox_error(struct sbrmi_data *data) {

Nit> Many functions only use data>client and, in some cases, dereference
Nit> it
several times. It might be easier to just pass 'client'.

> + int status;
> +
> + /* Mailbox error code will be written by Firmware in
> + * SBRMI::OutBndMsg_inst7 (SBRMI_x37)
> + */

/*
* Please use standard multi-line comments. Applies to entire driver.
*/

> + status = i2c_smbus_read_byte_data(data->client, SBRMI_OUTBNDMSG7);
> + if (status < 0) {
> + pr_err("SMBUS translation failed\n");
> + return status;
> + }
> +
> + switch (status) {
> + case 0x0: /* Success */
> + break;
> + case 0x1:
> + pr_err("Mailbox message command is aborted\n");
> + break;
> + case 0x2:
> + pr_err("Unknown mailbox message\n");
> + break;
> + case 0x3:
> + pr_err("Invalid core is specified in mailbox message parameters\n");
> + break;
> + default:
> + pr_err("Unknown Error\n");
> + }

Is this noise necessary ? I am concerned that, if it occurs, it would be persistent and fill up the kernel log with noise.

> +
> + return status;

Error codes are supposed to be negative and standard Linux error codes.
Please convert the above errors to standard Linux error codes.

> +}
> +
> +static int sbrmi_enable_alert(struct sbrmi_data *data) {
> + int ctrl;
> +
> + /* Enable the SB-RMI Software alert status
> + * by writing 0 to bit 4 of Control register(0x1)
> + */
> + ctrl = i2c_smbus_read_byte_data(data->client, SBRMI_CTRL);
> + if (ctrl < 0)
> + return ctrl;
> +
> + if (ctrl & 0x10) {
> + ctrl &= ~0x10;
> + return i2c_smbus_write_byte_data(data->client,
> + SBRMI_CTRL, ctrl);
> + }
> +
> + return 0;
> +}
> +
> +static int rmi_mailbox_xfer(struct sbrmi_data *data,
> + struct sbrmi_mailbox_msg *msg) {
> + union mailbox_word output, input;
> + int i, err = 0, retry = 10;

Initializing 'err' is unnecessary.

> + int sw_status;
> +
> + mutex_lock(&data->lock);
> +
> + err = sbrmi_enable_alert(data);
> + if (err < 0)
> + goto exit_unlock;
> +
> + /* Indicate firmware a command is to be serviced */
> + err = i2c_smbus_write_byte_data(data->client,
> + SBRMI_INBNDMSG7, START_CMD);
> + if (err < 0)
> + goto exit_unlock;
> +
> + /* Write the command to SBRMI::InBndMsg_inst0 */
> + err = i2c_smbus_write_byte_data(data->client,
> + SBRMI_INBNDMSG0, msg->cmd);
> + if (err < 0)
> + goto exit_mod;
> +
> + /*
> + * For both read and write the initiator (BMC) writes
> + * Command Data In[31:0] to SBRMI::InBndMsg_inst[4:1]
> + * SBRMI_x3C(MSB):SBRMI_x39(LSB)
> + */
> + input = msg->data_in;
> + for (i = 0; i < 3; i++) {

This writes 3 bytes. Is that on purpose ? If so please explain since the above suggests that 4 bytes should be written.

> + err = i2c_smbus_write_byte_data(data->client,
> + (SBRMI_INBNDMSG1 + i),

Unnecessary ( )

> + input.bytes[i]);
> + if (err < 0)
> + goto exit_mod;
> + }
> +
> + /*
> + * Write 0x01 to SBRMI::SoftwareInterrupt to notify firmware to
> + * perform the requested read or write command
> + */
> + err = i2c_smbus_write_byte_data(data->client,
> + SBRMI_SW_INTERRUPT, TRIGGER_MAILBOX);
> + if (err < 0)
> + goto exit_mod;
> +
> + /*
> + * Firmware will write SBRMI::Status[SwAlertSts]=1 to generate
> + * an ALERT (if enabled) to initiator (BMC) to indicate completion
> + * of the requested command
> + */
> + do {
> + sw_status = i2c_smbus_read_byte_data(data->client,
> + SBRMI_STATUS);
> + if (sw_status < 0) {
> + err = sw_status;
> + goto exit_mod;
> + }
> + if (sw_status & SW_ALERT_MASK)
> + break;
> + usleep_range(50, 100);
> + } while (retry--);
> +
> + if (retry < 0) {
> + pr_err("Firmware fail to indicate command
> + colmpletion\n");

completion

> + err = -1;
> + goto exit_mod;
> + }
> +
> + /*
> + * For a read operation, the initiator (BMC) reads the firmware response
> + * Command Data Out[31:0] from SBRMI::OutBndMsg_inst[4:1]
> + * {SBRMI_x34(MSB):SBRMI_x31(LSB)}.
> + */
> + if (msg->read) {
> + for (i = 0; i < 4; i++) {
> + output.bytes[i] = i2c_smbus_read_byte_data(data->client,
> +
> + (SBRMI_OUTBNDMSG1 + i));

Unnecessary ().

> + if (output.bytes[i] < 0) {

output.bytes is defined as u8. This will not catch errors.

> + err = output.bytes[i];
> + goto exit_mod;
> + }
> + }
> + }
> + msg->data_out = output;
> +
> + /*
> + * BMC must write 1'b1 to SBRMI::Status[SwAlertSts] to clear the
> + * ALERT to initiator
> + */
> + err = i2c_smbus_write_byte_data(data->client, SBRMI_STATUS,
> + (sw_status | SW_ALERT_MASK));

Unnecessary ().

> +
> +exit_mod:
> + if (err < 0)
> + pr_err("SMBUS translation failed\n");
> + else
> + err = print_mailbox_error(data);
> +exit_unlock:
> + mutex_unlock(&data->lock);
> + return err;
> +}
> +
> +static int sbrmi_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val) {
> + struct sbrmi_data *data = dev_get_drvdata(dev);
> + struct sbrmi_mailbox_msg msg = { 0 };
> + int ret;
> +
> + if (type != hwmon_power)
> + return -EINVAL;
> +
> + msg.read = true;
> + switch (attr) {
> + case hwmon_power_input:
> + msg.cmd = SBRMI_READ_PKG_PWR_CONSUMPTION;
> + ret = rmi_mailbox_xfer(data, &msg);
> + break;
> + case hwmon_power_cap:
> + msg.cmd = SBRMI_READ_PKG_PWR_LIMIT;
> + ret = rmi_mailbox_xfer(data, &msg);
> + break;
> + case hwmon_power_cap_max:
> + msg.cmd = SBRMI_READ_PKG_MAX_PWR_LIMIT;
> + ret = rmi_mailbox_xfer(data, &msg);
> + break;
> + default:
> + return -EINVAL;
> + }
> + /*
> + * hwmon power attributes are in microWatt
> + */
> + *val = (long)msg.data_out.value * 1000;
> + return ret;
> +}
> +
> +static int sbrmi_write(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long val) {
> + struct sbrmi_data *data = dev_get_drvdata(dev);
> + struct sbrmi_mailbox_msg msg = { 0 };
> +
> + if (type != hwmon_power && attr != hwmon_power_cap)
> + return -EINVAL;
> + /*
> + * hwmon power attributes are in microWatt
> + * mailbox read/write is in mWatt
> + */
> + val /= 1000;
> +
> + msg.cmd = SBRMI_READ_PKG_MAX_PWR_LIMIT;
> + msg.data_in.value = 0;
> + msg.read = true;
> + rmi_mailbox_xfer(data, &msg);
> +
> + val = clamp_val(val, SBRMI_PWR_MIN, msg.data_out.value);
> +
> + msg.cmd = SBRMI_WRITE_PKG_PWR_LIMIT;
> + msg.data_in.value = val;
> + msg.read = false;
> +
> + return rmi_mailbox_xfer(data, &msg); }
> +
> +static umode_t sbrmi_is_visible(const void *data,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel) {
> + switch (type) {
> + case hwmon_power:
> + switch (attr) {
> + case hwmon_power_input:
> + case hwmon_power_cap_max:
> + return 0444;
> + case hwmon_power_cap:
> + return 0644;
> + }
> + break;
> + default:
> + break;
> + }
> + return 0;
> +}
> +
> +static const struct hwmon_channel_info *sbrmi_info[] = {
> + HWMON_CHANNEL_INFO(power,
> + HWMON_P_INPUT | HWMON_P_CAP | HWMON_P_CAP_MAX),
> + NULL
> +};
> +
> +static const struct hwmon_ops sbrmi_hwmon_ops = {
> + .is_visible = sbrmi_is_visible,
> + .read = sbrmi_read,
> + .write = sbrmi_write,
> +};
> +
> +static const struct hwmon_chip_info sbrmi_chip_info = {
> + .ops = &sbrmi_hwmon_ops,
> + .info = sbrmi_info,
> +};
> +
> +static int sbrmi_probe(struct i2c_client *client,
> + const struct i2c_device_id *id) {
> + struct device *dev = &client->dev;
> + struct device *hwmon_dev;
> + struct sbrmi_data *data;
> +
> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> + dev_err(&client->dev, "adapter does not support true
> + I2C\n");

Why would that matter? It only uses SMBus functions.

> + return -ENODEV;
> + }
> +
> + data = devm_kzalloc(dev, sizeof(struct sbrmi_data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->client = client;
> + mutex_init(&data->lock);
> +
> + hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data,
> +
> + &sbrmi_chip_info, NULL);
> +
> + return PTR_ERR_OR_ZERO(hwmon_dev); }
> +
> +static const struct i2c_device_id sbrmi_id[] = {
> + {"sbrmi", 0},
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, sbrmi_id);
> +
> +static const struct of_device_id __maybe_unused sbrmi_of_match[] = {
> + {
> + .compatible = "amd,sbrmi",
> + },
> + { },
> +};
> +MODULE_DEVICE_TABLE(of, sbrmi_of_match);
> +
> +static struct i2c_driver sbrmi_driver = {
> + .class = I2C_CLASS_HWMON,
> + .driver = {
> + .name = "sbrmi",
> + .of_match_table = of_match_ptr(sbrmi_of_match),
> + },
> + .probe = sbrmi_probe,
> + .id_table = sbrmi_id,
> +};
> +
> +module_i2c_driver(sbrmi_driver);
> +
> +MODULE_AUTHOR("Akshay Gupta <akshay.gupta@amd.com>");
> +MODULE_DESCRIPTION("Hwmon driver for AMD SB-RMI emulated sensor");
> +MODULE_LICENSE("GPL");
[naveenk:] Thank you for your comments, we will address your comments and submit v2 soon.
>
[naveenk:]
Regards,
Naveenk