i2c-taos-evm: Switch echo off to improve performance
When echo is on, we waste time reading back our orders. Switching echo
off makes performance much better: SMBus byte data transactions are 47%
faster and byte transactions are 24% faster.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/i2c/busses/i2c-taos-evm.c b/drivers/i2c/busses/i2c-taos-evm.c
index 224aa12..dd39c1e 100644
--- a/drivers/i2c/busses/i2c-taos-evm.c
+++ b/drivers/i2c/busses/i2c-taos-evm.c
@@ -32,10 +32,12 @@
#define TAOS_STATE_INIT 0
#define TAOS_STATE_IDLE 1
-#define TAOS_STATE_SEND 2
+#define TAOS_STATE_EOFF 2
#define TAOS_STATE_RECV 3
#define TAOS_CMD_RESET 0x12
+#define TAOS_CMD_ECHO_ON '+'
+#define TAOS_CMD_ECHO_OFF '-'
static DECLARE_WAIT_QUEUE_HEAD(wq);
@@ -102,17 +104,9 @@
/* Send the transaction to the TAOS EVM */
dev_dbg(&adapter->dev, "Command buffer: %s\n", taos->buffer);
- taos->pos = 0;
- taos->state = TAOS_STATE_SEND;
- serio_write(serio, taos->buffer[0]);
- wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
- msecs_to_jiffies(250));
- if (taos->state != TAOS_STATE_IDLE) {
- dev_err(&adapter->dev, "Transaction failed "
- "(state=%d, pos=%d)\n", taos->state, taos->pos);
- taos->addr = 0;
- return -EIO;
- }
+ for (p = taos->buffer; *p; p++)
+ serio_write(serio, *p);
+
taos->addr = addr;
/* Start the transaction and read the answer */
@@ -122,7 +116,7 @@
wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
msecs_to_jiffies(150));
if (taos->state != TAOS_STATE_IDLE
- || taos->pos != 6) {
+ || taos->pos != 5) {
dev_err(&adapter->dev, "Transaction timeout (pos=%d)\n",
taos->pos);
return -EIO;
@@ -130,7 +124,7 @@
dev_dbg(&adapter->dev, "Answer buffer: %s\n", taos->buffer);
/* Interpret the returned string */
- p = taos->buffer + 2;
+ p = taos->buffer + 1;
p[3] = '\0';
if (!strcmp(p, "NAK"))
return -ENODEV;
@@ -173,13 +167,9 @@
wake_up_interruptible(&wq);
}
break;
- case TAOS_STATE_SEND:
- if (taos->buffer[++taos->pos])
- serio_write(serio, taos->buffer[taos->pos]);
- else {
- taos->state = TAOS_STATE_IDLE;
- wake_up_interruptible(&wq);
- }
+ case TAOS_STATE_EOFF:
+ taos->state = TAOS_STATE_IDLE;
+ wake_up_interruptible(&wq);
break;
case TAOS_STATE_RECV:
taos->buffer[taos->pos++] = data;
@@ -257,6 +247,19 @@
}
strlcpy(adapter->name, name, sizeof(adapter->name));
+ /* Turn echo off for better performance */
+ taos->state = TAOS_STATE_EOFF;
+ serio_write(serio, TAOS_CMD_ECHO_OFF);
+
+ wait_event_interruptible_timeout(wq, taos->state == TAOS_STATE_IDLE,
+ msecs_to_jiffies(250));
+ if (taos->state != TAOS_STATE_IDLE) {
+ err = -ENODEV;
+ dev_err(&adapter->dev, "Echo off failed "
+ "(state=%d)\n", taos->state);
+ goto exit_close;
+ }
+
err = i2c_add_adapter(adapter);
if (err)
goto exit_close;