libata: IDENTIFY backwards for drive side cable detection

For drive side cable detection to work correctly, drives need to be
identified backwards such that the slave device releases PDIAG- before
the mater drive tries to detect cable type.  ata_bus_probe() was fixed
by commit f31f0cc2f0b7527072d94d02da332d9bb8d7d94c but the new EH path
wasn't fixed.  This patch makes new EH path do IDENTIFY backwards.

ata_dev_configure() for new devices are still performed master first.
This is to keep the detection messages in forward order.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 42 insertions, 24 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 361953a50203..c89664a77a9c 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1743,12 +1743,17 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 {
         struct ata_eh_context *ehc = &ap->eh_context;
         struct ata_device *dev;
+        unsigned int new_mask = 0;
         unsigned long flags;
         int i, rc = 0;
 
         DPRINTK("ENTER\n");
 
-        for (i = 0; i < ATA_MAX_DEVICES; i++) {
+        /* For PATA drive side cable detection to work, IDENTIFY must
+         * be done backwards such that PDIAG- is released by the slave
+         * device before the master device is identified.
+         */
+        for (i = ATA_MAX_DEVICES - 1; i >= 0; i--) {
                 unsigned int action, readid_flags = 0;
 
                 dev = &ap->device[i];
@@ -1760,13 +1765,13 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
                 if (action & ATA_EH_REVALIDATE && ata_dev_ready(dev)) {
                         if (ata_port_offline(ap)) {
                                 rc = -EIO;
-                                break;
+                                goto err;
                         }
 
                         ata_eh_about_to_do(ap, dev, ATA_EH_REVALIDATE);
                         rc = ata_dev_revalidate(dev, readid_flags);
                         if (rc)
-                                break;
+                                goto err;
 
                         ata_eh_done(ap, dev, ATA_EH_REVALIDATE);
 
@@ -1784,40 +1789,53 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 
                         rc = ata_dev_read_id(dev, &dev->class, readid_flags,
                                              dev->id);
-                        if (rc == 0) {
-                                ehc->i.flags |= ATA_EHI_PRINTINFO;
-                                rc = ata_dev_configure(dev);
-                                ehc->i.flags &= ~ATA_EHI_PRINTINFO;
-                        } else if (rc == -ENOENT) {
+                        switch (rc) {
+                        case 0:
+                                new_mask |= 1 << i;
+                                break;
+                        case -ENOENT:
                                 /* IDENTIFY was issued to non-existent
                                  * device.  No need to reset.  Just
                                  * thaw and kill the device.
                                  */
                                 ata_eh_thaw_port(ap);
                                 dev->class = ATA_DEV_UNKNOWN;
-                                rc = 0;
-                        }
-
-                        if (rc) {
-                                dev->class = ATA_DEV_UNKNOWN;
                                 break;
+                        default:
+                                dev->class = ATA_DEV_UNKNOWN;
+                                goto err;
                         }
+                }
+        }
 
-                        if (ata_dev_enabled(dev)) {
-                                spin_lock_irqsave(ap->lock, flags);
-                                ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
-                                spin_unlock_irqrestore(ap->lock, flags);
+        /* Configure new devices forward such that user doesn't see
+         * device detection messages backwards.
+         */
+        for (i = 0; i < ATA_MAX_DEVICES; i++) {
+                dev = &ap->device[i];
 
-                                /* new device discovered, configure xfermode */
-                                ehc->i.flags |= ATA_EHI_SETMODE;
-                        }
-                }
+                if (!(new_mask & (1 << i)))
+                        continue;
+
+                ehc->i.flags |= ATA_EHI_PRINTINFO;
+                rc = ata_dev_configure(dev);
+                ehc->i.flags &= ~ATA_EHI_PRINTINFO;
+                if (rc)
+                        goto err;
+
+                spin_lock_irqsave(ap->lock, flags);
+                ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
+                spin_unlock_irqrestore(ap->lock, flags);
+
+                /* new device discovered, configure xfermode */
+                ehc->i.flags |= ATA_EHI_SETMODE;
         }
 
-        if (rc)
-                *r_failed_dev = dev;
+        return 0;
 
-        DPRINTK("EXIT\n");
+ err:
+        *r_failed_dev = dev;
+        DPRINTK("EXIT rc=%d\n", rc);
         return rc;
 }