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Commit fbcdd80b authored by Albert Lee's avatar Albert Lee Committed by Jeff Garzik
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[PATCH] libata irq-pio: eliminate unnecessary queuing in ata_pio_first_block() 



   - change the return value of ata_pio_complete() 0 <-> 1
   - add return value for ata_pio_first_block()
   - rename variable "qc_completed" to "has_next" in ata_pio_task()
   - use has_next to eliminate unnecessary queuing in ata_pio_first_block()

Signed-off-by: default avatarAlbert Lee <albertcc@tw.ibm.com>

==========
Signed-off-by: default avatarJeff Garzik <jgarzik@pobox.com>
parent e27486db

drivers/scsi/libata-core.c

+33 −20
Original line number Diff line number Diff line
@@ -2790,7 +2790,8 @@ static unsigned long ata_pio_poll(struct ata_port *ap) 
 *	None.  (executing in kernel thread context)

 *

 *	RETURNS:

 *	Non-zero if qc completed, zero otherwise.

 *	Zero if qc completed.

 *	Non-zero if has next.

 */



static int ata_pio_complete (struct ata_port *ap)
@@ -2812,14 +2813,14 @@ static int ata_pio_complete (struct ata_port *ap) 
		if (drv_stat & (ATA_BUSY | ATA_DRQ)) {

			ap->hsm_task_state = HSM_ST_LAST_POLL;

			ap->pio_task_timeout = jiffies + ATA_TMOUT_PIO;

			return 0;

			return 1;

		}

	}



	drv_stat = ata_wait_idle(ap);

	if (!ata_ok(drv_stat)) {

		ap->hsm_task_state = HSM_ST_ERR;

		return 0;

		return 1;

	}



	qc = ata_qc_from_tag(ap, ap->active_tag);
@@ -2831,7 +2832,7 @@ static int ata_pio_complete (struct ata_port *ap) 


	/* another command may start at this point */



	return 1;

	return 0;

}
@@ -3068,27 +3069,42 @@ static void atapi_send_cdb(struct ata_port *ap, struct ata_queued_cmd *qc) 
 *

 *	LOCKING:

 *	Kernel thread context (may sleep)

 *

 *	RETURNS:

 *	Zero if irq handler takes over

 *	Non-zero if has next (polling).

 */



static void ata_pio_first_block(struct ata_port *ap)

static int ata_pio_first_block(struct ata_port *ap)

{

	struct ata_queued_cmd *qc;

	u8 status;

	unsigned long flags;

	int has_next;



	qc = ata_qc_from_tag(ap, ap->active_tag);

	assert(qc != NULL);

	assert(qc->flags & ATA_QCFLAG_ACTIVE);



	/* if polling, we will stay in the work queue after sending the data.

	 * otherwise, interrupt handler takes over after sending the data.

	 */

	has_next = (qc->tf.flags & ATA_TFLAG_POLLING);



	/* sleep-wait for BSY to clear */

	DPRINTK("busy wait\n");

	if (ata_busy_sleep(ap, ATA_TMOUT_DATAOUT_QUICK, ATA_TMOUT_DATAOUT))

	if (ata_busy_sleep(ap, ATA_TMOUT_DATAOUT_QUICK, ATA_TMOUT_DATAOUT)) {

		ap->hsm_task_state = HSM_ST_TMOUT;

		goto err_out;

	}



	/* make sure DRQ is set */

	status = ata_chk_status(ap);

	if ((status & (ATA_BUSY | ATA_DRQ)) != ATA_DRQ)

	if ((status & (ATA_BUSY | ATA_DRQ)) != ATA_DRQ) {

		/* device status error */

		ap->hsm_task_state = HSM_ST_ERR;

		goto err_out;

	}



	/* Send the CDB (atapi) or the first data block (ata pio out).

	 * During the state transition, interrupt handler shouldn't
@@ -3112,18 +3128,15 @@ static void ata_pio_first_block(struct ata_port *ap) 
		/* send CDB */

		atapi_send_cdb(ap, qc);



	spin_unlock_irqrestore(&ap->host_set->lock, flags);



	/* if polling, ata_pio_task() handles the rest.

	 * otherwise, interrupt handler takes over from here.

	 */

	if (qc->tf.flags & ATA_TFLAG_POLLING)

		queue_work(ata_wq, &ap->pio_task);



	spin_unlock_irqrestore(&ap->host_set->lock, flags);



	return;

	return has_next;



err_out:

	ata_pio_error(ap);

	return 1; /* has next */

}



/**
@@ -3338,23 +3351,23 @@ static void ata_pio_task(void *_data) 
{

	struct ata_port *ap = _data;

	unsigned long timeout;

	int qc_completed;

	int has_next;



fsm_start:

	timeout = 0;

	qc_completed = 0;

	has_next = 1;



	switch (ap->hsm_task_state) {

	case HSM_ST_FIRST:

		ata_pio_first_block(ap);

		return;

		has_next = ata_pio_first_block(ap);

		break;



	case HSM_ST:

		ata_pio_block(ap);

		break;



	case HSM_ST_LAST:

		qc_completed = ata_pio_complete(ap);

		has_next = ata_pio_complete(ap);

		break;



	case HSM_ST_POLL:
@@ -3374,7 +3387,7 @@ static void ata_pio_task(void *_data) 


	if (timeout)

		queue_delayed_work(ata_wq, &ap->pio_task, timeout);

	else if (!qc_completed)

	else if (has_next)

		goto fsm_start;

}