From 27693ce5f372c0af3b0730f5152b35432afa0fd7 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Fri, 18 Sep 2009 22:45:43 +0200 Subject: [PATCH] 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 --- drivers/i2c/busses/i2c-taos-evm.c | 45 +++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 21 deletions(-) diff --git a/drivers/i2c/busses/i2c-taos-evm.c b/drivers/i2c/busses/i2c-taos-evm.c index 224aa12ee7c..dd39c1eb03e 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 @@ static int taos_smbus_xfer(struct i2c_adapter *adapter, u16 addr, /* 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 @@ static int taos_smbus_xfer(struct i2c_adapter *adapter, u16 addr, 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 @@ static int taos_smbus_xfer(struct i2c_adapter *adapter, u16 addr, 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 @@ static irqreturn_t taos_interrupt(struct serio *serio, unsigned char data, 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 @@ static int taos_connect(struct serio *serio, struct serio_driver *drv) } 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; -- 2.11.4.GIT