Revision 2be23c475af8ae4e25f8bab08d815b17593bd547 authored by Russell King on 08 September 2010, 15:27:56 UTC, committed by Russell King on 08 September 2010, 15:27:56 UTC
Dave Hylands reports: | We've observed a problem with dma_alloc_writecombine when the system | is under heavy load (heavy bus traffic). We've managed to reduce the | problem to the following snippet, which is run from a kthread in a | continuous loop: | | void *virtAddr; | dma_addr_t physAddr; | unsigned int numBytes = 256; | | for (;;) { | virtAddr = dma_alloc_writecombine(NULL, | numBytes, &physAddr, GFP_KERNEL); | if (virtAddr == NULL) { | printk(KERN_ERR "Running out of memory\n"); | break; | } | | /* access DMA memory allocated */ | tmp = virtAddr; | *tmp = 0x77; | | /* free DMA memory */ | dma_free_writecombine(NULL, | numBytes, virtAddr, physAddr); | | ...sleep here... | } | | By itself, the code will run forever with no issues. However, as we | increase our bus traffic (typically using DMA) then the *tmp = 0x77 | line will eventually cause a page fault. If we add a small delay (a | few microseconds) before the *tmp = 0x77, then we don't see a page | fault, even under heavy load. A dsb() is required after modifying the PTE entries to ensure that they will always be visible. Add this dsb(). Reported-by: Dave Hylands <dhylands@gmail.com> Tested-by: Dave Hylands <dhylands@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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88pm860x-i2c.c
/*
* I2C driver for Marvell 88PM860x
*
* Copyright (C) 2009 Marvell International Ltd.
* Haojian Zhuang <haojian.zhuang@marvell.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.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/mfd/88pm860x.h>
#include <linux/slab.h>
static inline int pm860x_read_device(struct i2c_client *i2c,
int reg, int bytes, void *dest)
{
unsigned char data;
int ret;
data = (unsigned char)reg;
ret = i2c_master_send(i2c, &data, 1);
if (ret < 0)
return ret;
ret = i2c_master_recv(i2c, dest, bytes);
if (ret < 0)
return ret;
return 0;
}
static inline int pm860x_write_device(struct i2c_client *i2c,
int reg, int bytes, void *src)
{
unsigned char buf[bytes + 1];
int ret;
buf[0] = (unsigned char)reg;
memcpy(&buf[1], src, bytes);
ret = i2c_master_send(i2c, buf, bytes + 1);
if (ret < 0)
return ret;
return 0;
}
int pm860x_reg_read(struct i2c_client *i2c, int reg)
{
struct pm860x_chip *chip = i2c_get_clientdata(i2c);
unsigned char data;
int ret;
mutex_lock(&chip->io_lock);
ret = pm860x_read_device(i2c, reg, 1, &data);
mutex_unlock(&chip->io_lock);
if (ret < 0)
return ret;
else
return (int)data;
}
EXPORT_SYMBOL(pm860x_reg_read);
int pm860x_reg_write(struct i2c_client *i2c, int reg,
unsigned char data)
{
struct pm860x_chip *chip = i2c_get_clientdata(i2c);
int ret;
mutex_lock(&chip->io_lock);
ret = pm860x_write_device(i2c, reg, 1, &data);
mutex_unlock(&chip->io_lock);
return ret;
}
EXPORT_SYMBOL(pm860x_reg_write);
int pm860x_bulk_read(struct i2c_client *i2c, int reg,
int count, unsigned char *buf)
{
struct pm860x_chip *chip = i2c_get_clientdata(i2c);
int ret;
mutex_lock(&chip->io_lock);
ret = pm860x_read_device(i2c, reg, count, buf);
mutex_unlock(&chip->io_lock);
return ret;
}
EXPORT_SYMBOL(pm860x_bulk_read);
int pm860x_bulk_write(struct i2c_client *i2c, int reg,
int count, unsigned char *buf)
{
struct pm860x_chip *chip = i2c_get_clientdata(i2c);
int ret;
mutex_lock(&chip->io_lock);
ret = pm860x_write_device(i2c, reg, count, buf);
mutex_unlock(&chip->io_lock);
return ret;
}
EXPORT_SYMBOL(pm860x_bulk_write);
int pm860x_set_bits(struct i2c_client *i2c, int reg,
unsigned char mask, unsigned char data)
{
struct pm860x_chip *chip = i2c_get_clientdata(i2c);
unsigned char value;
int ret;
mutex_lock(&chip->io_lock);
ret = pm860x_read_device(i2c, reg, 1, &value);
if (ret < 0)
goto out;
value &= ~mask;
value |= data;
ret = pm860x_write_device(i2c, reg, 1, &value);
out:
mutex_unlock(&chip->io_lock);
return ret;
}
EXPORT_SYMBOL(pm860x_set_bits);
static const struct i2c_device_id pm860x_id_table[] = {
{ "88PM860x", 0 },
{}
};
MODULE_DEVICE_TABLE(i2c, pm860x_id_table);
static int verify_addr(struct i2c_client *i2c)
{
unsigned short addr_8607[] = {0x30, 0x34};
unsigned short addr_8606[] = {0x10, 0x11};
int size, i;
if (i2c == NULL)
return 0;
size = ARRAY_SIZE(addr_8606);
for (i = 0; i < size; i++) {
if (i2c->addr == *(addr_8606 + i))
return CHIP_PM8606;
}
size = ARRAY_SIZE(addr_8607);
for (i = 0; i < size; i++) {
if (i2c->addr == *(addr_8607 + i))
return CHIP_PM8607;
}
return 0;
}
static int __devinit pm860x_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct pm860x_platform_data *pdata = client->dev.platform_data;
struct pm860x_chip *chip;
if (!pdata) {
pr_info("No platform data in %s!\n", __func__);
return -EINVAL;
}
chip = kzalloc(sizeof(struct pm860x_chip), GFP_KERNEL);
if (chip == NULL)
return -ENOMEM;
chip->id = verify_addr(client);
chip->client = client;
i2c_set_clientdata(client, chip);
chip->dev = &client->dev;
mutex_init(&chip->io_lock);
dev_set_drvdata(chip->dev, chip);
/*
* Both client and companion client shares same platform driver.
* Driver distinguishes them by pdata->companion_addr.
* pdata->companion_addr is only assigned if companion chip exists.
* At the same time, the companion_addr shouldn't equal to client
* address.
*/
if (pdata->companion_addr && (pdata->companion_addr != client->addr)) {
chip->companion_addr = pdata->companion_addr;
chip->companion = i2c_new_dummy(chip->client->adapter,
chip->companion_addr);
i2c_set_clientdata(chip->companion, chip);
}
pm860x_device_init(chip, pdata);
return 0;
}
static int __devexit pm860x_remove(struct i2c_client *client)
{
struct pm860x_chip *chip = i2c_get_clientdata(client);
pm860x_device_exit(chip);
i2c_unregister_device(chip->companion);
kfree(chip);
return 0;
}
static struct i2c_driver pm860x_driver = {
.driver = {
.name = "88PM860x",
.owner = THIS_MODULE,
},
.probe = pm860x_probe,
.remove = __devexit_p(pm860x_remove),
.id_table = pm860x_id_table,
};
static int __init pm860x_i2c_init(void)
{
int ret;
ret = i2c_add_driver(&pm860x_driver);
if (ret != 0)
pr_err("Failed to register 88PM860x I2C driver: %d\n", ret);
return ret;
}
subsys_initcall(pm860x_i2c_init);
static void __exit pm860x_i2c_exit(void)
{
i2c_del_driver(&pm860x_driver);
}
module_exit(pm860x_i2c_exit);
MODULE_DESCRIPTION("I2C Driver for Marvell 88PM860x");
MODULE_AUTHOR("Haojian Zhuang <haojian.zhuang@marvell.com>");
MODULE_LICENSE("GPL");
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