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at24: Use timeout also for read

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Writes may take some time on EEPROMs, so for consecutive writes, we already
have a loop waiting for the EEPROM to become ready. Use such a loop for reads,
too, in case somebody wants to immediately read after a write. Detailed bug
report and test case can be found here:

http://article.gmane.org/gmane.linux.drivers.i2c/4660

Reported-by: Aleksandar Ivanov <ivanov.aleks@gmail.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Tested-by: Aleksandar Ivanov <ivanov.aleks@gmail.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Wolfram Sang 2009-11-26 09:22:33 +01:00 committed by Jean Delvare
parent bbd2d9c919
commit 4d29196c53
1 changed files with 45 additions and 31 deletions
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52
drivers/misc/eeprom/at24.c
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@ -158,6 +158,7 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
struct i2c_msg msg[2]; struct i2c_msg msg[2];
u8 msgbuf[2]; u8 msgbuf[2];
struct i2c_client *client; struct i2c_client *client;
unsigned long timeout, read_time;
int status, i; int status, i;
memset(msg, 0, sizeof(msg)); memset(msg, 0, sizeof(msg));
@ -183,22 +184,17 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
if (count > io_limit) if (count > io_limit)
count = io_limit; count = io_limit;
/* Smaller eeproms can work given some SMBus extension calls */
if (at24->use_smbus) { if (at24->use_smbus) {
/* Smaller eeproms can work given some SMBus extension calls */
if (count > I2C_SMBUS_BLOCK_MAX) if (count > I2C_SMBUS_BLOCK_MAX)
count = I2C_SMBUS_BLOCK_MAX; count = I2C_SMBUS_BLOCK_MAX;
status = i2c_smbus_read_i2c_block_data(client, offset, } else {
count, buf);
dev_dbg(&client->dev, "smbus read %zu@%d --> %d\n",
count, offset, status);
return (status < 0) ? -EIO : status;
}
/* /*
* When we have a better choice than SMBus calls, use a combined * When we have a better choice than SMBus calls, use a
* I2C message. Write address; then read up to io_limit data bytes. * combined I2C message. Write address; then read up to
* Note that read page rollover helps us here (unlike writes). * io_limit data bytes. Note that read page rollover helps us
* msgbuf is u8 and will cast to our needs. * here (unlike writes). msgbuf is u8 and will cast to our
* needs.
*/ */
i = 0; i = 0;
if (at24->chip.flags & AT24_FLAG_ADDR16) if (at24->chip.flags & AT24_FLAG_ADDR16)
@ -213,17 +209,35 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
msg[1].flags = I2C_M_RD; msg[1].flags = I2C_M_RD;
msg[1].buf = buf; msg[1].buf = buf;
msg[1].len = count; msg[1].len = count;
}
/*
* Reads fail if the previous write didn't complete yet. We may
* loop a few times until this one succeeds, waiting at least
* long enough for one entire page write to work.
*/
timeout = jiffies + msecs_to_jiffies(write_timeout);
do {
read_time = jiffies;
if (at24->use_smbus) {
status = i2c_smbus_read_i2c_block_data(client, offset,
count, buf);
} else {
status = i2c_transfer(client->adapter, msg, 2); status = i2c_transfer(client->adapter, msg, 2);
dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n",
count, offset, status);
if (status == 2) if (status == 2)
status = count;
}
dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
count, offset, status, jiffies);
if (status == count)
return count; return count;
else if (status >= 0)
return -EIO; /* REVISIT: at HZ=100, this is sloooow */
else msleep(1);
return status; } while (time_before(read_time, timeout));
return -ETIMEDOUT;
} }
static ssize_t at24_read(struct at24_data *at24, static ssize_t at24_read(struct at24_data *at24,