[PATCH] libata: disable_irq() during polling IDENTIFY (take 2)

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

Problem:
  Kernel got "irq 5: nobody cared" when using
  libata + polling IDENTIFY + Promise 20275 adapter + Benq DW1620 drive.

  Detail message available in bug 8441 (http://bugzilla.kernel.org/show_bug.cgi?id=8441).

Cause:
  The Benq DW1620 drive raises INTRQ during polling IDENTIFY PACKET DEVICE, 
  even if nIEN = 1.

Proposed fix:
  Ack the possibly unexpected irq in ata_interrupt().

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
---
Patch revised per Tejun's advice to ack the unexpected INTRQ in ata_interrupt().
Also, ap->lock is held when transfering PIO data from/to the port in case the
device doesn't like the status register to be read during data transfer.

Patch against 2.6.21.1 for your review, thanks.

diff -Nrup linux-2.6.21.1-ori/drivers/ata/libata-core.c linux-2.6.21.1-mod6/drivers/ata/libata-core.c
--- linux-2.6.21.1-ori/drivers/ata/libata-core.c	2007-05-04 11:22:23.000000000 +0800
+++ linux-2.6.21.1-mod6/drivers/ata/libata-core.c	2007-05-08 19:25:58.000000000 +0800
@@ -4490,8 +4490,17 @@ fsm_start:
 				goto fsm_start;
 			}
 
+			/* prevent ata_interrupt() from reading
+			 * status when transfering data for safty
+			 */
+			if (in_wq)
+				spin_lock_irqsave(ap->lock, flags);
+
 			atapi_pio_bytes(qc);
 
+			if (in_wq)
+				spin_unlock_irqrestore(ap->lock, flags);
+
 			if (unlikely(ap->hsm_task_state == HSM_ST_ERR))
 				/* bad ireason reported by device */
 				goto fsm_start;
@@ -4529,12 +4538,21 @@ fsm_start:
 				/* data might be corrputed */
 				qc->err_mask |= AC_ERR_DEV;
 
+				/* prevent ata_interrupt() from reading
+				 * status when transfering data for safty
+				 */
+				if (in_wq)
+					spin_lock_irqsave(ap->lock, flags);
+
 				if (!(qc->tf.flags & ATA_TFLAG_WRITE)) {
 					ata_pio_sectors(qc);
 					ata_altstatus(ap);
 					status = ata_wait_idle(ap);
 				}
 
+				if (in_wq)
+					spin_unlock_irqrestore(ap->lock, flags);
+
 				if (status & (ATA_BUSY | ATA_DRQ))
 					qc->err_mask |= AC_ERR_HSM;
 
@@ -4546,8 +4564,17 @@ fsm_start:
 				goto fsm_start;
 			}
 
+			/* prevent ata_interrupt() from reading status
+			 * when transfering data for safty
+			 */
+			if (in_wq)
+				spin_lock_irqsave(ap->lock, flags);
+
 			ata_pio_sectors(qc);
 
+			if (in_wq)
+				spin_unlock_irqrestore(ap->lock, flags);
+
 			if (ap->hsm_task_state == HSM_ST_LAST &&
 			    (!(qc->tf.flags & ATA_TFLAG_WRITE))) {
 				/* all data read */
@@ -5227,6 +5254,9 @@ irqreturn_t ata_interrupt (int irq, void
 			if (qc && (!(qc->tf.flags & ATA_TFLAG_POLLING)) &&
 			    (qc->flags & ATA_QCFLAG_ACTIVE))
 				handled |= ata_host_intr(ap, qc);
+			else
+				/* ack possibly unexpected irq */
+				ata_chk_status(ap);
 		}
 	}