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hwmon: pmbus: Fix -EIO seen on pli1209

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After doing performance optimizations the pli1209 driver failed to
probe with a probabilty of 2%. It wasn't able to read the PMBUS_OPERATION
register due to an -EIO error.

An investigation showed that the PLI1209 takes 230 usec to execute the
CLEAR_FAULTS command. During that time it's busy and NACKs all requests
on the SMBUS interface. It also NACKs reads on PMBUS_STATUS_BYTE
making it impossible to poll the BUSY flag.

Add a custom write_data function to just wait for not BUSY unconditionally
after sending a CLEAR_FAULTS command.

TEST: Verified using an I2C bus analyser that no more NACKs are seen after
      sending a CLEAR_FAULTS command.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Link: https://lore.kernel.org/r/20230817092527.808631-3-Naresh.Solanki@9elements.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Patrick Rudolph 2023-08-17 11:25:26 +02:00 committed by Guenter Roeck
parent 3fd2188e58
commit e7593bda6a
1 changed files with 26 additions and 0 deletions
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26
drivers/hwmon/pmbus/pli1209bc.c
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@ -5,6 +5,7 @@
* Copyright (c) 2022 9elements GmbH
*/
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/pmbus.h>
@ -53,6 +54,30 @@ static int pli1209bc_read_word_data(struct i2c_client *client, int page,
}
}
static int pli1209bc_write_byte(struct i2c_client *client, int page, u8 reg)
{
int ret;
switch (reg) {
case PMBUS_CLEAR_FAULTS:
ret = pmbus_write_byte(client, page, reg);
/*
* PLI1209 takes 230 usec to execute the CLEAR_FAULTS command.
* During that time it's busy and NACKs all requests on the
* SMBUS interface. It also NACKs reads on PMBUS_STATUS_BYTE
* making it impossible to poll the BUSY flag.
*
* Just wait for not BUSY unconditionally.
*/
usleep_range(250, 300);
break;
default:
ret = -ENODATA;
break;
}
return ret;
}
#if IS_ENABLED(CONFIG_SENSORS_PLI1209BC_REGULATOR)
static const struct regulator_desc pli1209bc_reg_desc = {
.name = "vout2",
@ -102,6 +127,7 @@ static struct pmbus_driver_info pli1209bc_info = {
| PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
| PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_INPUT,
.read_word_data = pli1209bc_read_word_data,
.write_byte = pli1209bc_write_byte,
#if IS_ENABLED(CONFIG_SENSORS_PLI1209BC_REGULATOR)
.num_regulators = 1,
.reg_desc = &pli1209bc_reg_desc,