Commit 4d29196c authored by Wolfram Sang's avatar Wolfram Sang Committed by Jean Delvare
Browse files

at24: Use timeout also for read 

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: default avatarAleksandar Ivanov <ivanov.aleks@gmail.com>
Signed-off-by: default avatarWolfram Sang <w.sang@pengutronix.de>
Tested-by: default avatarAleksandar Ivanov <ivanov.aleks@gmail.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent bbd2d9c9

drivers/misc/eeprom/at24.c

+45 −31
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, 
	struct i2c_msg msg[2];

	u8 msgbuf[2];

	struct i2c_client *client;

	unsigned long timeout, read_time;

	int status, i;



	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)

		count = io_limit;



	/* Smaller eeproms can work given some SMBus extension calls */

	if (at24->use_smbus) {

		/* Smaller eeproms can work given some SMBus extension calls */

		if (count > I2C_SMBUS_BLOCK_MAX)

			count = I2C_SMBUS_BLOCK_MAX;

		status = i2c_smbus_read_i2c_block_data(client, offset,

				count, buf);

		dev_dbg(&client->dev, "smbus read %zu@%d --> %d\n",

				count, offset, status);

		return (status < 0) ? -EIO : status;

	}



	} else {

		/*

	 * When we have a better choice than SMBus calls, use a combined

	 * I2C message. Write address; then read up to io_limit data bytes.

	 * Note that read page rollover helps us here (unlike writes).

	 * msgbuf is u8 and will cast to our needs.

		 * When we have a better choice than SMBus calls, use a

		 * combined I2C message. Write address; then read up to

		 * io_limit data bytes. Note that read page rollover helps us

		 * here (unlike writes). msgbuf is u8 and will cast to our

		 * needs.

		 */

		i = 0;

		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].buf = buf;

		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);

	dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n",

			count, offset, status);



			if (status == 2)

				status = count;

		}

		dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",

				count, offset, status, jiffies);



		if (status == count)

			return count;

	else if (status >= 0)

		return -EIO;

	else

		return status;



		/* REVISIT: at HZ=100, this is sloooow */

		msleep(1);

	} while (time_before(read_time, timeout));



	return -ETIMEDOUT;

}



static ssize_t at24_read(struct at24_data *at24,

CRA Git | Maintained and supported by SUSTech CRA and CCSE