[PATCH linux dev-4.13 3/3] i2c: fsi: Use usleep instead of schedule calls

[Eddie James]

Simplify the FSI I2C driver by calling usleep_range while waiting for
data to be made available instead of scheduling a timeout. The schedule
overhead isn't worth it for what should be a short time.

Signed-off-by: Eddie James <eajames at linux.vnet.ibm.com>
---
 drivers/i2c/busses/i2c-fsi.c | 26 ++++++--------------------
 1 file changed, 6 insertions(+), 20 deletions(-)

diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
index adc2e38..52a662c 100644
--- a/drivers/i2c/busses/i2c-fsi.c
+++ b/drivers/i2c/busses/i2c-fsi.c
@@ -20,7 +20,6 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
-#include <linux/sched.h>
 
 #define FSI_ENGID_I2C		0x7
 
@@ -135,7 +134,8 @@
 
 #define I2C_PORT_BUSY_RESET	0x80000000
 
-#define I2C_LOCAL_WAIT_TIMEOUT	2		/* jiffies */
+#define I2C_LOCAL_SLEEP_MAX_US	500
+#define I2C_LOCAL_SLEEP_MIN_US	50
 
 /* choose timeout length from legacy driver; it's well tested */
 #define I2C_ABORT_TIMEOUT	msecs_to_jiffies(100)
@@ -490,10 +490,7 @@ static int fsi_i2c_abort(struct fsi_i2c_port *port, u32 status)
 		if (status & I2C_STAT_CMD_COMP)
 			return 0;
 
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (schedule_timeout(I2C_LOCAL_WAIT_TIMEOUT) > 0)
-			return -EINTR;
-
+		usleep_range(I2C_LOCAL_SLEEP_MIN_US, I2C_LOCAL_SLEEP_MAX_US);
 	} while (time_after(start + I2C_ABORT_TIMEOUT, jiffies));
 
 	return -ETIME;
@@ -556,7 +553,7 @@ static int fsi_i2c_wait(struct fsi_i2c_port *port, struct i2c_msg *msg,
 			unsigned long timeout)
 {
 	u32 status = 0;
-	int rc, rc_abort;
+	int rc;
 	unsigned long start = jiffies;
 
 	do {
@@ -578,21 +575,10 @@ static int fsi_i2c_wait(struct fsi_i2c_port *port, struct i2c_msg *msg,
 			continue;
 		}
 
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (schedule_timeout(I2C_LOCAL_WAIT_TIMEOUT) > 0) {
-			rc = -EINTR;
-			goto abort;
-		}
+		usleep_range(I2C_LOCAL_SLEEP_MIN_US, I2C_LOCAL_SLEEP_MAX_US);
 	} while (time_after(start + timeout, jiffies));
 
-	rc = -ETIME;
-
-abort:
-	rc_abort = fsi_i2c_abort(port, status);
-	if (rc_abort)
-		return rc_abort;
-
-	return rc;
+	return -ETIME;
 }
 
 static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
-- 
1.8.3.1