diff mbox

[RESEND,v2,04/13] eeprom: at24: make locking more fine-grained

Message ID 1460401049-25459-5-git-send-email-bgolaszewski@baylibre.com
State New
Headers show

Commit Message

Bartosz Golaszewski April 11, 2016, 6:57 p.m. UTC 
The only field in struct at24_data that needs locking in the module
code is u8 *writebuf. Other data is already protected by i2c core.

Rename the lock in at24_data to wrbuf_lock and only use it where
writebuf is accessed.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

---
 drivers/misc/eeprom/at24.c | 28 +++++-----------------------
 1 file changed, 5 insertions(+), 23 deletions(-)

-- 
2.7.4

Comments

Bartosz Golaszewski May 3, 2016, 5:55 p.m. UTC | #1 
2016-04-16 22:56 GMT+02:00 Wolfram Sang <wsa@the-dreams.de>:
> On Mon, Apr 11, 2016 at 11:57:20AM -0700, Bartosz Golaszewski wrote:

>> The only field in struct at24_data that needs locking in the module

>> code is u8 *writebuf. Other data is already protected by i2c core.

>>

>> Rename the lock in at24_data to wrbuf_lock and only use it where

>> writebuf is accessed.

>>

>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

>

> Did you run some tests to verify our assumption?

>


Hi Wolfram,

I had done concurrent read/write tests on a chip using i2c operations,
but I carried this patch over from before porting at24 to nvmem. I
didn't notice previously, but currently all read/write operations are
protected by the regmap lock in regmap_raw_write()/read().

There's no need for any locking in the driver anymore. I'll remove the
mutex altogether in the next version of the patchset.

Speaking of which: I don't think I'll find the time to complete the
driver rework before the next merge window. Would you mind picking up
patches [2/13] & [3/13] for 4.7?

Best regards,
Bartosz Golaszewski
diff mbox

Patch

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 744c526..9e01428 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -59,13 +59,8 @@  struct at24_data {
 	int use_smbus;
 	int use_smbus_write;
 
-	/*
-	 * Lock protects against activities from other Linux tasks,
-	 * but not from changes by other I2C masters.
-	 */
-	struct mutex lock;
-
 	u8 *writebuf;
+	struct mutex wrbuf_lock;
 	unsigned write_max;
 	unsigned num_addresses;
 
@@ -260,12 +255,6 @@  static ssize_t at24_read(struct at24_data *at24,
 	if (unlikely(!count))
 		return count;
 
-	/*
-	 * Read data from chip, protecting against concurrent updates
-	 * from this host, but not from other I2C masters.
-	 */
-	mutex_lock(&at24->lock);
-
 	while (count) {
 		ssize_t	status;
 
@@ -281,8 +270,6 @@  static ssize_t at24_read(struct at24_data *at24,
 		retval += status;
 	}
 
-	mutex_unlock(&at24->lock);
-
 	return retval;
 }
 
@@ -322,6 +309,8 @@  static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 		msg.addr = client->addr;
 		msg.flags = 0;
 
+		mutex_lock(&at24->wrbuf_lock);
+
 		/* msg.buf is u8 and casts will mask the values */
 		msg.buf = at24->writebuf;
 		if (at24->chip.flags & AT24_FLAG_ADDR16)
@@ -356,6 +345,7 @@  static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 				status = count;
 		} else {
 			status = i2c_transfer(client->adapter, &msg, 1);
+			mutex_unlock(&at24->wrbuf_lock);
 			if (status == 1)
 				status = count;
 		}
@@ -380,12 +370,6 @@  static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 	if (unlikely(!count))
 		return count;
 
-	/*
-	 * Write data to chip, protecting against concurrent updates
-	 * from this host, but not from other I2C masters.
-	 */
-	mutex_lock(&at24->lock);
-
 	while (count) {
 		ssize_t	status;
 
@@ -401,8 +385,6 @@  static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 		retval += status;
 	}
 
-	mutex_unlock(&at24->lock);
-
 	return retval;
 }
 
@@ -566,7 +548,7 @@  static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	if (!at24)
 		return -ENOMEM;
 
-	mutex_init(&at24->lock);
+	mutex_init(&at24->wrbuf_lock);
 	at24->use_smbus = use_smbus;
 	at24->use_smbus_write = use_smbus_write;
 	at24->chip = chip;