[PATCH] x86: Fix verify_quirk_intel_irqbalance()

Fix verify_quirk_intel_irqbalance(). genapic checks should really
happen only on affected versions of the E7520/E7320/E7525 based platforms.

AK: This should akpm's Coyote SDV

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/i386/kernel/quirks.c

@@ -10,13 +10,38 @@
 #if defined(CONFIG_X86_IO_APIC) && defined(CONFIG_SMP) && defined(CONFIG_PCI)
 static void __devinit verify_quirk_intel_irqbalance(struct pci_dev *dev)
 {
+	u8 config, rev;
+	u32 word;
+
+	/* BIOS may enable hardware IRQ balancing for
+	 * E7520/E7320/E7525(revision ID 0x9 and below)
+	 * based platforms.
+	 * For those platforms, make sure that the genapic is set to 'flat'
+	 */
+	pci_read_config_byte(dev, PCI_CLASS_REVISION, &rev);
+	if (rev > 0x9)
+		return;
+
+	/* enable access to config space*/
+	pci_read_config_byte(dev, 0xf4, &config);
+	pci_write_config_byte(dev, 0xf4, config|0x2);
+
+	/* read xTPR register */
+	raw_pci_ops->read(0, 0, 0x40, 0x4c, 2, &word);
+
+	if (!(word & (1 << 13))) {
 #ifdef CONFIG_X86_64
-	if (genapic !=  &apic_flat)
-		panic("APIC mode must be flat on this system\n");
+		if (genapic !=  &apic_flat)
+			panic("APIC mode must be flat on this system\n");
 #elif defined(CONFIG_X86_GENERICARCH)
-	if (genapic != &apic_default)
-		panic("APIC mode must be default(flat) on this system. Use apic=default\n");
+		if (genapic != &apic_default)
+			panic("APIC mode must be default(flat) on this system. Use apic=default\n");
 #endif
+	}
+
+	/* put back the original value for config space*/
+	if (!(config & 0x2))
+		pci_write_config_byte(dev, 0xf4, config);
 }
 
 void __init quirk_intel_irqbalance(void)