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Commit 27693ce5 authored by Jean Delvare's avatar Jean Delvare
Browse files

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: default avatarJean Delvare <khali@linux-fr.org>
parent 6a891a31

drivers/i2c/busses/i2c-taos-evm.c

+24 −21
Original line number Diff line number Diff line
@@ -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 {

	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;