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i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()

PATCH Applied Alexander Sverdlin 3 participants 6 messages May 13, 2015 – Jun 10, 2015 2 messages not in the archive

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I2C subsystem host drivers TI DaVinci machine support
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Alexander Sverdlin

author
#0 lore raw

PATCH v2 1/1 i2c: davinci: Refactor i2c_davinci_wait_bus_not_busy()

There are several problems in the function:
- "to_cnt" variable does nothing
- schedule_timeout() call without setting current state does nothing
- "allow_sleep" parameter is not really used

Refactor the function so that it really tries to wait. In case of timeout try to recover the bus.

Signed-off-by Alexander Sverdlin <[email protected]>

---
Changes in v2:
- rebased on 110bc76729d4 of Linus's tree;

 drivers/i2c/busses/i2c-davinci.c |   42 +++++++++++++++++--------------------
 1 files changed, 19 insertions(+), 23 deletions(-)
drivers/i2c/busses/i2c-davinci.c +19 -23
index df96ab6..03afdee 100644
@@ -350,29 +350,25 @@ static struct i2c_bus_recovery_info davinci_i2c_scl_recovery_info = {
 /*
  * Waiting for bus not busy
  */
-static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
-					 char allow_sleep)
+static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev)
 {
-	unsigned long timeout;
-	static u16 to_cnt;
-
-	timeout = jiffies + dev->adapter.timeout;
-	while (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG)
-	       & DAVINCI_I2C_STR_BB) {
-		if (to_cnt <= DAVINCI_I2C_MAX_TRIES) {
-			if (time_after(jiffies, timeout)) {
-				dev_warn(dev->dev,
-				"timeout waiting for bus ready\n");
-				to_cnt++;
-				return -ETIMEDOUT;
-			} else {
-				to_cnt = 0;
-				i2c_recover_bus(&dev->adapter);
-			}
-		}
-		if (allow_sleep)
-			schedule_timeout(1);
-	}
+	unsigned long timeout = jiffies + dev->adapter.timeout;
+
+	do {
+		if (!(davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB))
+			return 0;
+		schedule_timeout_uninterruptible(1);
+	} while (time_before_eq(jiffies, timeout));
+
+	dev_warn(dev->dev, "timeout waiting for bus ready\n");
+	i2c_recover_bus(dev);
+
+	/*
+	 * if bus is still "busy" here, it's most probably a HW problem like
+	 * short-circuit
+	 */
+	if (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB)
+		return -EIO;
 
 	return 0;
 }

@@ -508,7 +504,7 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 
 	dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);
 
-	ret = i2c_davinci_wait_bus_not_busy(dev, 1);
+	ret = i2c_davinci_wait_bus_not_busy(dev);
 	if (ret < 0) {
 		dev_warn(dev->dev, "timeout waiting for bus ready\n");
 		return ret;
Reviewed-by
#2 lore raw
In reply to a message not in the archive
Quoted 7 lines · Alexander Sverdlin

There are several problems in the function:
- "to_cnt" variable does nothing
- schedule_timeout() call without setting current state does nothing
- "allow_sleep" parameter is not really used

Refactor the function so that it really tries to wait. In case of timeout try to recover the bus.

Reviewed-by Grygorii Strashko <[email protected]>
Quoted 7 lines
Signed-off-by Alexander Sverdlin <[email protected]>

---
Changes in v2:
- rebased on 110bc76729d4 of Linus's tree;

  drivers/i2c/busses/i2c-davinci.c |   42 +++++++++++++++++--------------------
  1 files changed, 19 insertions(+), 23 deletions(-)
Signature · 2 lines
regards,
-grygorii
#3 lore raw
In reply to a message not in the archive
Quoted 9 lines · Alexander Sverdlin

There are several problems in the function:
- "to_cnt" variable does nothing
- schedule_timeout() call without setting current state does nothing
- "allow_sleep" parameter is not really used

Refactor the function so that it really tries to wait. In case of timeout try to recover the bus.

Signed-off-by Alexander Sverdlin <[email protected]>

Don't you get a build warning?

drivers/i2c/busses/i2c-davinci.c: In function 'i2c_davinci_wait_bus_not_busy':
drivers/i2c/busses/i2c-davinci.c:364:18: warning: passing argument 1 of 'i2c_recover_bus' from incompatible pointer type

  i2c_recover_bus(dev);
                  ^

In file included from drivers/i2c/busses/i2c-davinci.c:26:0:
include/linux/i2c.h:446:5: note: expected 'struct i2c_adapter *' but argument is of type 'struct davinci_i2c_dev *'
int i2c_recover_bus(struct i2c_adapter *adap);

Or sparse complains, too:

drivers/i2c/busses/i2c-davinci.c:364:25: warning: incorrect type in argument 1 (different base types)
drivers/i2c/busses/i2c-davinci.c:364:25: expected struct i2c_adapter *adap
drivers/i2c/busses/i2c-davinci.c:364:25: got struct davinci_i2c_dev *dev

author
#4 lore raw

Hello Wolfram,

Quoted 11 lines · ext Wolfram Sang
Quoted 9 lines

There are several problems in the function:

Quoted 8 lines

- "to_cnt" variable does nothing
- schedule_timeout() call without setting current state does nothing
- "allow_sleep" parameter is not really used

Refactor the function so that it really tries to wait. In case of timeout try to recover the bus.

Signed-off-by Alexander Sverdlin <[email protected]>

Don't you get a build warning?

Quoted 7 lines

drivers/i2c/busses/i2c-davinci.c: In function 'i2c_davinci_wait_bus_not_busy':
drivers/i2c/busses/i2c-davinci.c:364:18: warning: passing argument 1 of 'i2c_recover_bus' from incompatible pointer type

  i2c_recover_bus(dev);
                  ^

In file included from drivers/i2c/busses/i2c-davinci.c:26:0:
include/linux/i2c.h:446:5: note: expected 'struct i2c_adapter *' but argument is of type 'struct davinci_i2c_dev *'
int i2c_recover_bus(struct i2c_adapter *adap);

oh, this is awful copy-paster error... I'll re-send!

Signature · 2 lines
Best regards,
Alexander Sverdlin.
author
#5 lore raw
In reply to a message not in the archive

There are several problems in the function:
- "to_cnt" variable does nothing
- schedule_timeout() call without setting current state does nothing
- "allow_sleep" parameter is not really used

Refactor the function so that it really tries to wait. In case of timeout try to recover the bus.

Signed-off-by Alexander Sverdlin <[email protected]>

---
Changes in v3:
- corrected argument of i2c_recover_bus()
Changes in v2:
- rebased on 110bc76729d4 of Linus's tree;

 drivers/i2c/busses/i2c-davinci.c |   42 +++++++++++++++++--------------------
 1 files changed, 19 insertions(+), 23 deletions(-)
drivers/i2c/busses/i2c-davinci.c +19 -23
index df96ab6..03afdee 100644
@@ -350,29 +350,25 @@ static struct i2c_bus_recovery_info davinci_i2c_scl_recovery_info = {
 /*
  * Waiting for bus not busy
  */
-static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
-					 char allow_sleep)
+static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev)
 {
-	unsigned long timeout;
-	static u16 to_cnt;
-
-	timeout = jiffies + dev->adapter.timeout;
-	while (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG)
-	       & DAVINCI_I2C_STR_BB) {
-		if (to_cnt <= DAVINCI_I2C_MAX_TRIES) {
-			if (time_after(jiffies, timeout)) {
-				dev_warn(dev->dev,
-				"timeout waiting for bus ready\n");
-				to_cnt++;
-				return -ETIMEDOUT;
-			} else {
-				to_cnt = 0;
-				i2c_recover_bus(&dev->adapter);
-			}
-		}
-		if (allow_sleep)
-			schedule_timeout(1);
-	}
+	unsigned long timeout = jiffies + dev->adapter.timeout;
+
+	do {
+		if (!(davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB))
+			return 0;
+		schedule_timeout_uninterruptible(1);
+	} while (time_before_eq(jiffies, timeout));
+
+	dev_warn(dev->dev, "timeout waiting for bus ready\n");
+	i2c_recover_bus(&dev->adapter);
+
+	/*
+	 * if bus is still "busy" here, it's most probably a HW problem like
+	 * short-circuit
+	 */
+	if (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB)
+		return -EIO;
 
 	return 0;
 }

@@ -508,7 +504,7 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 
 	dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);
 
-	ret = i2c_davinci_wait_bus_not_busy(dev, 1);
+	ret = i2c_davinci_wait_bus_not_busy(dev);
 	if (ret < 0) {
 		dev_warn(dev->dev, "timeout waiting for bus ready\n");
 		return ret;