Fix take a long time on IDE probe. fix bug 4678.

Kernel is hanging for a long time on probing the IDE, even
when there's no hard disk connected. This patch fix a bug,
Now we can pass parameters to kernel to skip drive probing
if none exist.
Summary of ide driver parameters for kernel command line:
"hdx=noprobe"  : drive may be present, but don't probe for it

arch/arm/configs/ntosd_644xA_defconfig

@@ -496,7 +496,7 @@ CONFIG_BLK_DEV_RAM_BLOCKSIZE=1024
 # CONFIG_CDROM_PKTCDVD is not set
 # CONFIG_ATA_OVER_ETH is not set
 CONFIG_IDE=y
-CONFIG_IDE_MAX_HWIFS=4
+CONFIG_IDE_MAX_HWIFS=1
 CONFIG_BLK_DEV_IDE=y
 
 #

drivers/ide/ide-probe.c

@@ -643,6 +643,7 @@ static void hwif_register (ide_hwif_t *hwif)
 static int wait_hwif_ready(ide_hwif_t *hwif)
 {
 	int rc;
+	unsigned int unit;
 
 	printk(KERN_DEBUG "Probing IDE interface %s...\n", hwif->name);
 
@@ -659,16 +660,24 @@ static int wait_hwif_ready(ide_hwif_t *hwif)
 		return rc;
 
 	/* Now make sure both master & slave are ready */
-	SELECT_DRIVE(&hwif->drives[0]);
+    for (unit = 0; unit < MAX_DRIVES; ++unit) {
+            /* Ignore disks that we will not probe for later. */
+            if (!hwif->drives[unit].noprobe ||
+                hwif->drives[unit].present) {
+                    SELECT_DRIVE(&hwif->drives[unit]);
                     hwif->OUTB(8, hwif->io_ports[IDE_CONTROL_OFFSET]);
                     mdelay(2);
                     rc = ide_wait_not_busy(hwif, 35000);
-	if (rc)
+                    if (rc) {
+                            /* Exit function with master reselected */
+                            if (unit != 0)
+                                    SELECT_DRIVE(&hwif->drives[0]);
                             return rc;
-	SELECT_DRIVE(&hwif->drives[1]);
-	hwif->OUTB(8, hwif->io_ports[IDE_CONTROL_OFFSET]);
-	mdelay(2);
-	rc = ide_wait_not_busy(hwif, 35000);
+                    }
+            } else {
+                    printk("Skip ide_wait_not_busy for %s:%d\n",hwif->name, unit);
+            }
+    }
 
 	/* Exit function with master reselected (let's be sane) */
 	SELECT_DRIVE(&hwif->drives[0]);
@@ -723,8 +732,6 @@ static void probe_hwif(ide_hwif_t *hwif, void (*fixup)(ide_hwif_t *hwif))
 	unsigned long flags;
 	unsigned int irqd;
 
-    if(!hwif->present)
-        return;
 	if (hwif->noprobe)
 		return;
 

drivers/ide/ide.c

@@ -121,9 +121,16 @@ EXPORT_SYMBOL(ide_hwifs);
 static void init_hwif_data(ide_hwif_t *hwif, unsigned int index)
 {
 	unsigned int unit;
+	unsigned int noprobe[MAX_DRIVES];
 
 	/* bulk initialize hwif & drive info with zeros */
+	for(unit = 0; unit < MAX_DRIVES; unit++) {
+		noprobe[unit] = hwif->drives[unit].noprobe;
+	}
 	memset(hwif, 0, sizeof(ide_hwif_t));
+	for(unit = 0; unit < MAX_DRIVES; unit++) {
+		hwif->drives[unit].noprobe = noprobe[unit];
+	}
 
 	/* fill in any non-zero initial values */
 	hwif->index	= index;