Commit e7593bda authored by Patrick Rudolph's avatar Patrick Rudolph Committed by Guenter Roeck
Browse files

hwmon: pmbus: Fix -EIO seen on pli1209 



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: default avatarPatrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: default avatarNaresh Solanki <Naresh.Solanki@9elements.com>
Link: https://lore.kernel.org/r/20230817092527.808631-3-Naresh.Solanki@9elements.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 3fd2188e

drivers/hwmon/pmbus/pli1209bc.c

+26 −0
Original line number Diff line number Diff line
@@ -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,