From 205e0c0577faec05f5a9b92349cfd3454f2b00ec Mon Sep 17 00:00:00 2001 From: Lakshmi Yadlapati Date: Thu, 26 Oct 2023 23:43:46 -0500 Subject: [PATCH] hwmon: (pmbus/max31785) Add delay between bus accesses The MAX31785 has shown erratic behaviour across multiple system designs, unexpectedly clock stretching and NAKing transactions. Experimentation shows that this seems to be triggered by a register access directly back to back with a previous register write. Experimentation also shows that inserting a small delay after register writes makes the issue go away. Use a similar solution to what the max15301 driver does to solve the same problem. Create a custom set of bus read and write functions that make sure that the delay is added. Signed-off-by: Lakshmi Yadlapati Link: https://lore.kernel.org/r/20231027044346.2167548-1-lakshmiy@us.ibm.com Signed-off-by: Guenter Roeck --- drivers/hwmon/pmbus/max31785.c | 188 +++++++++++++++++++++++++++++---- 1 file changed, 167 insertions(+), 21 deletions(-) diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c index f9aa576495a5..5d13bbfc8f47 100644 --- a/drivers/hwmon/pmbus/max31785.c +++ b/drivers/hwmon/pmbus/max31785.c @@ -3,6 +3,7 @@ * Copyright (C) 2017 IBM Corp. */ +#include #include #include #include @@ -23,19 +24,119 @@ enum max31785_regs { #define MAX31785_NR_PAGES 23 #define MAX31785_NR_FAN_PAGES 6 +#define MAX31785_WAIT_DELAY_US 250 -static int max31785_read_byte_data(struct i2c_client *client, int page, - int reg) +struct max31785_data { + ktime_t access; /* Chip access time */ + struct pmbus_driver_info info; +}; + +#define to_max31785_data(x) container_of(x, struct max31785_data, info) + +/* + * MAX31785 Driver Workaround + * + * The MAX31785 fan controller occasionally exhibits communication issues. + * These issues are not indicated by the device itself, except for occasional + * NACK responses during master transactions. No error bits are set in STATUS_BYTE. + * + * To address this, we introduce a delay of 250us between consecutive accesses + * to the fan controller. This delay helps mitigate communication problems by + * allowing sufficient time between accesses. + */ +static inline void max31785_wait(const struct max31785_data *data) { - if (page < MAX31785_NR_PAGES) - return -ENODATA; + s64 delta = ktime_us_delta(ktime_get(), data->access); + + if (delta < MAX31785_WAIT_DELAY_US) + usleep_range(MAX31785_WAIT_DELAY_US - delta, + MAX31785_WAIT_DELAY_US); +} + +static int max31785_i2c_write_byte_data(struct i2c_client *client, + struct max31785_data *driver_data, + int command, u16 data) +{ + int rc; + + max31785_wait(driver_data); + rc = i2c_smbus_write_byte_data(client, command, data); + driver_data->access = ktime_get(); + return rc; +} + +static int max31785_i2c_read_word_data(struct i2c_client *client, + struct max31785_data *driver_data, + int command) +{ + int rc; + + max31785_wait(driver_data); + rc = i2c_smbus_read_word_data(client, command); + driver_data->access = ktime_get(); + return rc; +} + +static int _max31785_read_byte_data(struct i2c_client *client, + struct max31785_data *driver_data, + int page, int command) +{ + int rc; + + max31785_wait(driver_data); + rc = pmbus_read_byte_data(client, page, command); + driver_data->access = ktime_get(); + return rc; +} + +static int _max31785_write_byte_data(struct i2c_client *client, + struct max31785_data *driver_data, + int page, int command, u16 data) +{ + int rc; + + max31785_wait(driver_data); + rc = pmbus_write_byte_data(client, page, command, data); + driver_data->access = ktime_get(); + return rc; +} + +static int _max31785_read_word_data(struct i2c_client *client, + struct max31785_data *driver_data, + int page, int phase, int command) +{ + int rc; + + max31785_wait(driver_data); + rc = pmbus_read_word_data(client, page, phase, command); + driver_data->access = ktime_get(); + return rc; +} + +static int _max31785_write_word_data(struct i2c_client *client, + struct max31785_data *driver_data, + int page, int command, u16 data) +{ + int rc; + + max31785_wait(driver_data); + rc = pmbus_write_word_data(client, page, command, data); + driver_data->access = ktime_get(); + return rc; +} + +static int max31785_read_byte_data(struct i2c_client *client, int page, int reg) +{ + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct max31785_data *driver_data = to_max31785_data(info); switch (reg) { case PMBUS_VOUT_MODE: return -ENOTSUPP; case PMBUS_FAN_CONFIG_12: - return pmbus_read_byte_data(client, page - MAX31785_NR_PAGES, - reg); + return _max31785_read_byte_data(client, driver_data, + page - MAX31785_NR_PAGES, + reg); } return -ENODATA; @@ -102,16 +203,19 @@ static int max31785_get_pwm(struct i2c_client *client, int page) return rv; } -static int max31785_get_pwm_mode(struct i2c_client *client, int page) +static int max31785_get_pwm_mode(struct i2c_client *client, + struct max31785_data *driver_data, int page) { int config; int command; - config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12); + config = _max31785_read_byte_data(client, driver_data, page, + PMBUS_FAN_CONFIG_12); if (config < 0) return config; - command = pmbus_read_word_data(client, page, 0xff, PMBUS_FAN_COMMAND_1); + command = _max31785_read_word_data(client, driver_data, page, 0xff, + PMBUS_FAN_COMMAND_1); if (command < 0) return command; @@ -129,6 +233,8 @@ static int max31785_get_pwm_mode(struct i2c_client *client, int page) static int max31785_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 max31785_data *driver_data = to_max31785_data(info); u32 val; int rv; @@ -157,7 +263,7 @@ static int max31785_read_word_data(struct i2c_client *client, int page, rv = max31785_get_pwm(client, page); break; case PMBUS_VIRT_PWM_ENABLE_1: - rv = max31785_get_pwm_mode(client, page); + rv = max31785_get_pwm_mode(client, driver_data, page); break; default: rv = -ENODATA; @@ -188,8 +294,36 @@ static inline u32 max31785_scale_pwm(u32 sensor_val) return (sensor_val * 100) / 255; } -static int max31785_pwm_enable(struct i2c_client *client, int page, - u16 word) +static int max31785_update_fan(struct i2c_client *client, + struct max31785_data *driver_data, int page, + u8 config, u8 mask, u16 command) +{ + int from, rv; + u8 to; + + from = _max31785_read_byte_data(client, driver_data, page, + PMBUS_FAN_CONFIG_12); + if (from < 0) + return from; + + to = (from & ~mask) | (config & mask); + + if (to != from) { + rv = _max31785_write_byte_data(client, driver_data, page, + PMBUS_FAN_CONFIG_12, to); + if (rv < 0) + return rv; + } + + rv = _max31785_write_word_data(client, driver_data, page, + PMBUS_FAN_COMMAND_1, command); + + return rv; +} + +static int max31785_pwm_enable(struct i2c_client *client, + struct max31785_data *driver_data, int page, + u16 word) { int config = 0; int rate; @@ -217,18 +351,23 @@ static int max31785_pwm_enable(struct i2c_client *client, int page, return -EINVAL; } - return pmbus_update_fan(client, page, 0, config, PB_FAN_1_RPM, rate); + return max31785_update_fan(client, driver_data, page, config, + PB_FAN_1_RPM, rate); } static int max31785_write_word_data(struct i2c_client *client, int page, int reg, u16 word) { + const struct pmbus_driver_info *info = pmbus_get_driver_info(client); + struct max31785_data *driver_data = to_max31785_data(info); + switch (reg) { case PMBUS_VIRT_PWM_1: - return pmbus_update_fan(client, page, 0, 0, PB_FAN_1_RPM, - max31785_scale_pwm(word)); + return max31785_update_fan(client, driver_data, page, 0, + PB_FAN_1_RPM, + max31785_scale_pwm(word)); case PMBUS_VIRT_PWM_ENABLE_1: - return max31785_pwm_enable(client, page, word); + return max31785_pwm_enable(client, driver_data, page, word); default: break; } @@ -303,13 +442,16 @@ static int max31785_configure_dual_tach(struct i2c_client *client, { int ret; int i; + struct max31785_data *driver_data = to_max31785_data(info); for (i = 0; i < MAX31785_NR_FAN_PAGES; i++) { - ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i); + ret = max31785_i2c_write_byte_data(client, driver_data, + PMBUS_PAGE, i); if (ret < 0) return ret; - ret = i2c_smbus_read_word_data(client, MFR_FAN_CONFIG); + ret = max31785_i2c_read_word_data(client, driver_data, + MFR_FAN_CONFIG); if (ret < 0) return ret; @@ -329,6 +471,7 @@ static int max31785_probe(struct i2c_client *client) { struct device *dev = &client->dev; struct pmbus_driver_info *info; + struct max31785_data *driver_data; bool dual_tach = false; int ret; @@ -337,13 +480,16 @@ static int max31785_probe(struct i2c_client *client) I2C_FUNC_SMBUS_WORD_DATA)) return -ENODEV; - info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL); - if (!info) + driver_data = devm_kzalloc(dev, sizeof(struct max31785_data), GFP_KERNEL); + if (!driver_data) return -ENOMEM; + info = &driver_data->info; + driver_data->access = ktime_get(); *info = max31785_info; - ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 255); + ret = max31785_i2c_write_byte_data(client, driver_data, + PMBUS_PAGE, 255); if (ret < 0) return ret; -- 2.25.1