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authorWolfram Sang <w.sang@pengutronix.de>2009-11-26 09:22:33 +0100
committerJean Delvare <khali@linux-fr.org>2009-11-26 09:22:33 +0100
commit4d29196c535088e807061ce2a0aa526daec2edfb (patch)
tree960fbfa00bb0372a6be425b8131dd4d937e5d0d8 /drivers/misc/eeprom
parentbbd2d9c9198c6efd449e9d395b3eaf2d03aa3bba (diff)
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: 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>
Diffstat (limited to 'drivers/misc/eeprom')
-rw-r--r--drivers/misc/eeprom/at24.c76
1 files changed, 45 insertions, 31 deletions
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index db39f4a52f5..2cb2736d65a 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -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));
@@ -183,47 +184,60 @@ 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.
+ */
+ i = 0;
+ if (at24->chip.flags & AT24_FLAG_ADDR16)
+ msgbuf[i++] = offset >> 8;
+ msgbuf[i++] = offset;
+
+ msg[0].addr = client->addr;
+ msg[0].buf = msgbuf;
+ msg[0].len = i;
+
+ msg[1].addr = client->addr;
+ msg[1].flags = I2C_M_RD;
+ msg[1].buf = buf;
+ msg[1].len = count;
}
/*
- * 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.
+ * 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.
*/
- i = 0;
- if (at24->chip.flags & AT24_FLAG_ADDR16)
- msgbuf[i++] = offset >> 8;
- msgbuf[i++] = offset;
-
- msg[0].addr = client->addr;
- msg[0].buf = msgbuf;
- msg[0].len = i;
+ 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);
+ if (status == 2)
+ status = count;
+ }
+ dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
+ count, offset, status, jiffies);
- msg[1].addr = client->addr;
- msg[1].flags = I2C_M_RD;
- msg[1].buf = buf;
- msg[1].len = count;
+ if (status == count)
+ return count;
- status = i2c_transfer(client->adapter, msg, 2);
- dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n",
- count, offset, status);
+ /* REVISIT: at HZ=100, this is sloooow */
+ msleep(1);
+ } while (time_before(read_time, timeout));
- if (status == 2)
- return count;
- else if (status >= 0)
- return -EIO;
- else
- return status;
+ return -ETIMEDOUT;
}
static ssize_t at24_read(struct at24_data *at24,