[PATCH/RFC 5/9] libata: use freeze()/thaw() for polling

[Albert Lee <albertcc@tw.ibm.com>]

Patch 5/9:

  This patch changes polling codes to use freeze()/thaw() for irq off/on.
ata_qc_set_polling() is also removed since now unused.

The reason for freeze()/thaw(): some ATAPI devices raises INTRQ even if nIEN = 1.
Using the host adapter irq mask mechanism, if available, is more reliable than using the device nIEN bit.

Considerations:
 1. the semantic of freeze()/thaw() maybe more than irq off/on?
 2. HSM, the new user of freeze()/thaw(), will call freeze()/thaw() more frequently than EH.
    Can current implemention of freeze()/thaw() handle it?

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

diff -Nrup 04_convert_freeze/drivers/ata/libata-core.c 05_convert_hsm_to_freeze/drivers/ata/libata-core.c
--- 04_convert_freeze/drivers/ata/libata-core.c	2007-06-11 17:37:24.000000000 +0800
+++ 05_convert_hsm_to_freeze/drivers/ata/libata-core.c	2007-06-12 13:33:03.000000000 +0800
@@ -4753,7 +4753,7 @@ static void ata_hsm_qc_complete(struct a
 			qc = ata_qc_from_tag(ap, qc->tag);
 			if (qc) {
 				if (likely(!(qc->err_mask & AC_ERR_HSM))) {
-					ap->ops->irq_on(ap);
+					ap->ops->thaw(ap);
 					ata_qc_complete(qc);
 				} else
 					ata_port_freeze(ap);
@@ -4769,7 +4769,7 @@ static void ata_hsm_qc_complete(struct a
 	} else {
 		if (in_wq) {
 			spin_lock_irqsave(ap->lock, flags);
-			ap->ops->irq_on(ap);
+			ap->ops->thaw(ap);
 			ata_qc_complete(qc);
 			spin_unlock_irqrestore(ap->lock, flags);
 		} else
@@ -5421,7 +5421,7 @@ unsigned int ata_qc_issue_prot(struct at
 	switch (qc->tf.protocol) {
 	case ATA_PROT_NODATA:
 		if (qc->tf.flags & ATA_TFLAG_POLLING)
-			ata_qc_set_polling(qc);
+			ap->ops->freeze(ap);
 
 		ata_tf_to_host(ap, &qc->tf);
 		ap->hsm_task_state = HSM_ST_LAST;
@@ -5442,7 +5442,7 @@ unsigned int ata_qc_issue_prot(struct at
 
 	case ATA_PROT_PIO:
 		if (qc->tf.flags & ATA_TFLAG_POLLING)
-			ata_qc_set_polling(qc);
+			ap->ops->freeze(ap);
 
 		ata_tf_to_host(ap, &qc->tf);
 
@@ -5471,7 +5471,7 @@ unsigned int ata_qc_issue_prot(struct at
 	case ATA_PROT_ATAPI:
 	case ATA_PROT_ATAPI_NODATA:
 		if (qc->tf.flags & ATA_TFLAG_POLLING)
-			ata_qc_set_polling(qc);
+			ap->ops->freeze(ap);
 
 		ata_tf_to_host(ap, &qc->tf);
 
diff -Nrup 04_convert_freeze/include/linux/libata.h 05_convert_hsm_to_freeze/include/linux/libata.h
--- 04_convert_freeze/include/linux/libata.h	2007-06-11 17:37:24.000000000 +0800
+++ 05_convert_hsm_to_freeze/include/linux/libata.h	2007-06-12 13:40:14.000000000 +0800
@@ -1100,11 +1100,6 @@ static inline u8 ata_wait_idle(struct at
 	return status;
 }
 
-static inline void ata_qc_set_polling(struct ata_queued_cmd *qc)
-{
-	qc->tf.ctl |= ATA_NIEN;
-}
-
 static inline struct ata_queued_cmd *__ata_qc_from_tag(struct ata_port *ap,
 						       unsigned int tag)
 {