linux/drivers/power/supply/bq27xxx_battery_hdq.c

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/*
* BQ27xxx battery monitor HDQ/1-wire driver
*
* Copyright (C) 2007-2017 Texas Instruments Incorporated - https://www.ti.com/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed "as is" WITHOUT ANY WARRANTY of any
* kind, whether express or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/power/bq27xxx_battery.h>
#include <linux/w1.h>
#define W1_FAMILY_BQ27000 0x01
#define HDQ_CMD_READ (0 << 7)
#define HDQ_CMD_WRITE (1 << 7)
static int F_ID;
module_param(F_ID, int, S_IRUSR);
MODULE_PARM_DESC(F_ID, "1-wire slave FID for BQ27xxx device");
static int w1_bq27000_read(struct w1_slave *sl, unsigned int reg)
{
u8 val;
W1: split master mutex to avoid deadlocks. The 'mutex' in struct w1_master is use for two very different purposes. Firstly it protects various data structures such as the list of all slaves. Secondly it protects the w1 buss against concurrent accesses. This can lead to deadlocks when the ->probe code called while adding a slave needs to talk on the bus, as is the case for power_supply devices. ds2780 and ds2781 drivers contain a work around to track which process hold the lock simply to avoid this deadlock. bq27000 doesn't have that work around and so deadlocks. There are other possible deadlocks involving sysfs. When removing a device the sysfs s_active lock is held, so the lock that protects the slave list must take precedence over s_active. However when access power_supply attributes via sysfs, the s_active lock must take precedence over the lock that protects accesses to the bus. So to avoid deadlocks between w1 slaves and sysfs, these must be two separate locks. Making them separate means that the work around in ds2780 and ds2781 can be removed. So this patch: - adds a new mutex: "bus_mutex" which serialises access to the bus. - takes in mutex in w1_search and ds1wm_search while they access the bus for searching. The mutex is dropped before calling the callback which adds the slave. - changes all slaves to use bus_mutex instead of mutex to protect access to the bus - removes w1_ds2790_io_nolock and w1_ds2781_io_nolock, and the related code from drivers/power/ds278[01]_battery.c which calls them. Signed-off-by: NeilBrown <neilb@suse.de> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-05-18 13:59:52 +08:00
mutex_lock(&sl->master->bus_mutex);
w1_write_8(sl->master, HDQ_CMD_READ | reg);
val = w1_read_8(sl->master);
W1: split master mutex to avoid deadlocks. The 'mutex' in struct w1_master is use for two very different purposes. Firstly it protects various data structures such as the list of all slaves. Secondly it protects the w1 buss against concurrent accesses. This can lead to deadlocks when the ->probe code called while adding a slave needs to talk on the bus, as is the case for power_supply devices. ds2780 and ds2781 drivers contain a work around to track which process hold the lock simply to avoid this deadlock. bq27000 doesn't have that work around and so deadlocks. There are other possible deadlocks involving sysfs. When removing a device the sysfs s_active lock is held, so the lock that protects the slave list must take precedence over s_active. However when access power_supply attributes via sysfs, the s_active lock must take precedence over the lock that protects accesses to the bus. So to avoid deadlocks between w1 slaves and sysfs, these must be two separate locks. Making them separate means that the work around in ds2780 and ds2781 can be removed. So this patch: - adds a new mutex: "bus_mutex" which serialises access to the bus. - takes in mutex in w1_search and ds1wm_search while they access the bus for searching. The mutex is dropped before calling the callback which adds the slave. - changes all slaves to use bus_mutex instead of mutex to protect access to the bus - removes w1_ds2790_io_nolock and w1_ds2781_io_nolock, and the related code from drivers/power/ds278[01]_battery.c which calls them. Signed-off-by: NeilBrown <neilb@suse.de> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-05-18 13:59:52 +08:00
mutex_unlock(&sl->master->bus_mutex);
return val;
}
static int bq27xxx_battery_hdq_read(struct bq27xxx_device_info *di, u8 reg,
bool single)
{
struct w1_slave *sl = dev_to_w1_slave(di->dev);
unsigned int timeout = 3;
int upper, lower;
int temp;
if (!single) {
/*
* Make sure the value has not changed in between reading the
* lower and the upper part
*/
upper = w1_bq27000_read(sl, reg + 1);
do {
temp = upper;
if (upper < 0)
return upper;
lower = w1_bq27000_read(sl, reg);
if (lower < 0)
return lower;
upper = w1_bq27000_read(sl, reg + 1);
} while (temp != upper && --timeout);
if (timeout == 0)
return -EIO;
return (upper << 8) | lower;
}
return w1_bq27000_read(sl, reg);
}
static int bq27xxx_battery_hdq_add_slave(struct w1_slave *sl)
{
struct bq27xxx_device_info *di;
di = devm_kzalloc(&sl->dev, sizeof(*di), GFP_KERNEL);
if (!di)
return -ENOMEM;
dev_set_drvdata(&sl->dev, di);
di->dev = &sl->dev;
di->chip = BQ27000;
di->name = "bq27000-battery";
di->bus.read = bq27xxx_battery_hdq_read;
return bq27xxx_battery_setup(di);
}
static void bq27xxx_battery_hdq_remove_slave(struct w1_slave *sl)
{
struct bq27xxx_device_info *di = dev_get_drvdata(&sl->dev);
bq27xxx_battery_teardown(di);
}
static struct w1_family_ops bq27xxx_battery_hdq_fops = {
.add_slave = bq27xxx_battery_hdq_add_slave,
.remove_slave = bq27xxx_battery_hdq_remove_slave,
};
static struct w1_family bq27xxx_battery_hdq_family = {
.fid = W1_FAMILY_BQ27000,
.fops = &bq27xxx_battery_hdq_fops,
};
static int __init bq27xxx_battery_hdq_init(void)
{
if (F_ID)
bq27xxx_battery_hdq_family.fid = F_ID;
return w1_register_family(&bq27xxx_battery_hdq_family);
}
module_init(bq27xxx_battery_hdq_init);
static void __exit bq27xxx_battery_hdq_exit(void)
{
w1_unregister_family(&bq27xxx_battery_hdq_family);
}
module_exit(bq27xxx_battery_hdq_exit);
MODULE_AUTHOR("Texas Instruments Ltd");
MODULE_DESCRIPTION("BQ27xxx battery monitor HDQ/1-wire driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("w1-family-" __stringify(W1_FAMILY_BQ27000));