[PATCH] hpet: Enable hidden HPET on NVidia motherboards

[Mikko Tiihonen <mikko.tiihonen@iki.fi>]

Enables HPET for NVidia motherboards with broken BIOS. The patch reads the 
HPET address from the pci config space. The patch should also work if ACPI is 
disabled.

The HPET search is done in early-quirks because even DECLARE_PCI_FIXUP_EARLY 
was too late. If the new quirk causes problems it can be disabled with the
nohpet boot option.

The patch assumes that the BIOS has done the basic setup of HPET, but has not 
published the result in ACPI tables. This is at least true for some Asus and 
Gigabyte motherboards.

Patch is against 2.6.21-rc6-git7 but should apply cleanly to most kernels.

Signed-off-by: Mikko Tiihonen <mikko.tiihonen@iki.fi>

---

It looks probable that most NVidia chipsets have the HPET address at 0x44. It 
might be possible to enable the HPET even if BIOS did not initialize it 
properly by writing the wanted address there. Some other pci config space bits 
might need to be fiddled around too, most likely candidates are 0x74 bit 2 and 
0xA3 bit ?. One or both of them have been identified to change in some 
motherboards when HPET is enabled/disabled in BIOS.

--- arch/x86_64/kernel/early-quirks.c.orig	2007-04-16 01:30:33.000000000 +0300
+++ arch/x86_64/kernel/early-quirks.c	2007-04-16 01:27:23.000000000 +0300
@@ -15,6 +15,7 @@
 #include <asm/pci-direct.h>
 #include <asm/proto.h>
 #include <asm/dma.h>
+#include <linux/bootmem.h>

 static void __init via_bugs(void)
 {
@@ -36,6 +37,104 @@ static int __init nvidia_hpet_check(stru
 }
 #endif

+#ifdef CONFIG_HPET
+
+static u32 nvidia_hpet_chips[] __initdata = {
+	/* ISA Bridge */
+	PCI_VENDOR_ID_NVIDIA | (0x0050 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0051 << 16),
+	/* LPC Bridge */
+	PCI_VENDOR_ID_NVIDIA | (0x0360 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0361 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0362 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0363 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0364 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0365 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0366 << 16),
+	PCI_VENDOR_ID_NVIDIA | (0x0367 << 16),
+	0,
+};
+
+static int __init force_enable_nvidia_hpet(void)
+{
+	int num, slot, func;
+	u32 addr;
+	struct resource *hpet_res;
+
+	if (hpet_address || nohpet)
+		return 0;
+
+	/* Poor man's PCI discovery */
+	for (num = 0; num < 32; num++) {
+		for (slot = 0; slot < 32; slot++) {
+			for (func = 0; func < 8; func++) {
+				u32 class;
+				u32 vendor;
+				u8 type;
+				int i;
+				class = read_pci_config(num,slot,func,
+							PCI_CLASS_REVISION);
+				if (class == 0xffffffff)
+					break;
+				vendor = read_pci_config(num, slot, func,
+							 PCI_VENDOR_ID);
+
+				for (i = 0; nvidia_hpet_chips[i]; i++)
+					if (nvidia_hpet_chips[i] == vendor) {
+						goto found;
+					}
+
+				type = read_pci_config_byte(num, slot, func,
+							    PCI_HEADER_TYPE);
+				if (!(type & 0x80))
+					break;
+			}
+		}
+	}
+	return 0;
+
+ found:
+	addr = read_pci_config(num, slot, func, 0x44);
+	if (!addr) {
+		return 0;
+	}
+
+#define HPET_RESOURCE_NAME_SIZE 12
+	hpet_res = alloc_bootmem(sizeof(*hpet_res) + HPET_RESOURCE_NAME_SIZE);
+	if (!hpet_res) {
+		/* We could try writing to the 0x44 and see if that is enough
+		 * to enable HPET even if BIOS did not initialize it.
+		 */
+		printk(KERN_INFO "HPET not set up by BIOS.\n");
+		return 0;
+	}
+
+	memset(hpet_res, 0, sizeof(*hpet_res));
+	hpet_res->name = (void *)&hpet_res[1];
+	hpet_res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	strncpy((char *)hpet_res->name, "NVidia HPET", 
+		HPET_RESOURCE_NAME_SIZE);
+	hpet_res->start = addr;
+	hpet_res->end = hpet_res->start + HPET_MMAP_SIZE - 1;
+
+	if (request_resource(&iomem_resource, hpet_res)) {
+		printk(KERN_INFO "NVidia quirk failed. Could not "
+		       "reserve resources for HPET at base: %#x\n", addr);
+		return 0;
+	}
+
+	hpet_address = addr;
+	printk(KERN_INFO "NVidia quirk. Enabled hidden HPET that BIOS had "
+	       "configured at base: %#x\n", addr);
+	return 1;
+}
+#else
+static int __init force_enable_nvidia_hpet(void)
+{
+	return 0;
+}
+#endif
+
 static void __init nvidia_bugs(void)
 {
 #ifdef CONFIG_ACPI
@@ -50,6 +149,10 @@ static void __init nvidia_bugs(void)
 		return;

 	if (acpi_table_parse(ACPI_SIG_HPET, nvidia_hpet_check)) {
+		if (force_enable_nvidia_hpet()) {
+			return;
+		}
+
 		acpi_skip_timer_override = 1;
 		printk(KERN_INFO "Nvidia board "
 		       "detected. Ignoring ACPI "
@@ -57,6 +160,8 @@ static void __init nvidia_bugs(void)
 		printk(KERN_INFO "If you got timer trouble "
 			"try acpi_use_timer_override\n");
 	}
+#else
+	force_enable_nvidia_hpet();
 #endif
 	/* RED-PEN skip them on mptables too? */


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