[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: Albert Lee <albertcc@tw.ibm.com>
==========
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 96b8bba..2e0e6cc 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -2790,7 +2790,8 @@
* 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 @@
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 @@
/* another command may start at this point */
- return 1;
+ return 0;
}
@@ -3068,27 +3069,42 @@
*
* 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 @@
/* 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 @@
{
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 @@
if (timeout)
queue_delayed_work(ata_wq, &ap->pio_task, timeout);
- else if (!qc_completed)
+ else if (has_next)
goto fsm_start;
}