[PATCH] Fix HPET operation on 32-bit NVIDIA platforms

From: "Andy Currid" <ACurrid@nvidia.com>

This patch fixes a kernel panic during boot that occurs on NVIDIA platforms
that have HPET enabled.

When HPET is enabled, the standard timer IRQ is routed to IOAPIC pin 2 and is
advertised as such in the ACPI APIC table - but an earlier workaround in the
kernel was ignoring this override.  The fix is to honor timer IRQ overrides
from ACPI when HPET is detected on an NVIDIA platform.
Signed-off-by: Andy Currid <acurrid@nvidia.com>
Cc: "Brown, Len" <len.brown@intel.com>
Cc: "Yu, Luming" <luming.yu@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/acpi/earlyquirk.c

@@ -5,18 +5,35 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
+#include <linux/acpi.h>
+
 #include <asm/pci-direct.h>
 #include <asm/acpi.h>
 #include <asm/apic.h>
 
+#ifdef CONFIG_ACPI
+
+static int nvidia_hpet_detected __initdata;
+
+static int __init nvidia_hpet_check(unsigned long phys, unsigned long size)
+{
+	nvidia_hpet_detected = 1;
+	return 0;
+}
+#endif
+
 static int __init check_bridge(int vendor, int device)
 {
 #ifdef CONFIG_ACPI
-	/* According to Nvidia all timer overrides are bogus. Just ignore
-	   them all. */
+	/* According to Nvidia all timer overrides are bogus unless HPET
+	   is enabled. */
 	if (vendor == PCI_VENDOR_ID_NVIDIA) {
+		nvidia_hpet_detected = 0;
+		acpi_table_parse(ACPI_HPET, nvidia_hpet_check);
+		if (nvidia_hpet_detected == 0) {
 			acpi_skip_timer_override = 1;
 		}
+	}
 #endif
 	if (vendor == PCI_VENDOR_ID_ATI && timer_over_8254 == 1) {
 		timer_over_8254 = 0;

arch/i386/kernel/setup.c

@@ -1547,15 +1547,18 @@ void __init setup_arch(char **cmdline_p)
 	if (efi_enabled)
 		efi_map_memmap();
 
-#ifdef CONFIG_X86_IO_APIC
-	check_acpi_pci();	/* Checks more than just ACPI actually */
-#endif
-
 #ifdef CONFIG_ACPI
 	/*
 	 * Parse the ACPI tables for possible boot-time SMP configuration.
 	 */
 	acpi_boot_table_init();
+#endif
+
+#ifdef CONFIG_X86_IO_APIC
+	check_acpi_pci();	/* Checks more than just ACPI actually */
+#endif
+
+#ifdef CONFIG_ACPI
 	acpi_boot_init();
 
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_PC)