[PATCH] libata-dev: fix the device err check sequence (respin)

Current irq-pio checks ERR bit and stops on ERR before it does anything else.
This behavior doesn't look right.
The DRQ bit should take higher precedence than the ERR bit.

Changes:
- Let the HSM do the data transfer whenever the
  device asks for DRQ bit, even if the ERR bit is set.
- For DRQ=1 ERR=1, don't trust the data

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 38 insertions, 6 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index d68f5d5b423a..59cb12993f95 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -3587,12 +3587,6 @@ static int ata_hsm_move(struct ata_port *ap, struct ata_queued_cmd *qc,
          */
         WARN_ON(in_wq != ata_hsm_ok_in_wq(ap, qc));
 
-        /* check error */
-        if (unlikely(status & (ATA_ERR | ATA_DF))) {
-                qc->err_mask |= AC_ERR_DEV;
-                ap->hsm_task_state = HSM_ST_ERR;
-        }
-
 fsm_start:
         DPRINTK("ata%u: protocol %d task_state %d (dev_stat 0x%X)\n",
                 ap->id, qc->tf.protocol, ap->hsm_task_state, status);
@@ -3615,6 +3609,17 @@ fsm_start:
                         goto fsm_start;
                 }
 
+                /* Device should not ask for data transfer (DRQ=1)
+                 * when it finds something wrong.
+                 * Anyway, we respect DRQ here and let HSM go on
+                 * without changing hsm_task_state to HSM_ST_ERR.
+                 */
+                if (unlikely(status & (ATA_ERR | ATA_DF))) {
+                        printk(KERN_WARNING "ata%d: DRQ=1 with device error, dev_stat 0x%X\n",
+                               ap->id, status);
+                        qc->err_mask |= AC_ERR_DEV;
+                }
+
                 /* Send the CDB (atapi) or the first data block (ata pio out).
                  * During the state transition, interrupt handler shouldn't
                  * be invoked before the data transfer is complete and
@@ -3657,6 +3662,17 @@ fsm_start:
                                 goto fsm_start;
                         }
 
+                        /* Device should not ask for data transfer (DRQ=1)
+                         * when it finds something wrong.
+                         * Anyway, we respect DRQ here and let HSM go on
+                         * without changing hsm_task_state to HSM_ST_ERR.
+                         */
+                        if (unlikely(status & (ATA_ERR | ATA_DF))) {
+                                printk(KERN_WARNING "ata%d: DRQ=1 with device error, dev_stat 0x%X\n",
+                                       ap->id, status);
+                                qc->err_mask |= AC_ERR_DEV;
+                        }
+
                         atapi_pio_bytes(qc);
 
                         if (unlikely(ap->hsm_task_state == HSM_ST_ERR))
@@ -3672,6 +3688,22 @@ fsm_start:
                                 goto fsm_start;
                         }
 
+                        /* Some devices may ask for data transfer (DRQ=1)
+                         * alone with ERR=1 for PIO reads.
+                         * We respect DRQ here and let HSM go on without
+                         * changing hsm_task_state to HSM_ST_ERR.
+                         */
+                        if (unlikely(status & (ATA_ERR | ATA_DF))) {
+                                /* For writes, ERR=1 DRQ=1 doesn't make
+                                 * sense since the data block has been
+                                 * transferred to the device.
+                                 */
+                                WARN_ON(qc->tf.flags & ATA_TFLAG_WRITE);
+
+                                /* data might be corrputed */
+                                qc->err_mask |= AC_ERR_DEV;
+                        }
+
                         ata_pio_sectors(qc);
 
                         if (ap->hsm_task_state == HSM_ST_LAST &&