x86: Disable HPET MSI on ATI SB700/SB800

HPET MSI on platforms with ATI SB700/SB800 as they seem to have some
side-effects on floppy DMA. Do not use HPET MSI on such platforms.

Original problem report from Mark Hounschell
http://lkml.indiana.edu/hypermail/linux/kernel/0912.2/01118.html

[ This patch needs to go to stable as well. But, there are some
  conflicts that prevents the patch from going as is. I can
  rebase/resubmit to stable once the patch goes upstream.
  hpa: still Cc:'ing stable@ as an FYI. ]

Tested-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: <stable@kernel.org>
LKML-Reference: <20100121190952.GA32523@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/hpet.h

@@ -67,6 +67,7 @@ extern unsigned long hpet_address;
 extern unsigned long force_hpet_address;
 extern u8 hpet_blockid;
 extern int hpet_force_user;
+extern u8 hpet_msi_disable;
 extern int is_hpet_enabled(void);
 extern int hpet_enable(void);
 extern void hpet_disable(void);

arch/x86/kernel/hpet.c

@@ -34,6 +34,8 @@
  */
 unsigned long				hpet_address;
 u8					hpet_blockid; /* OS timer block num */
+u8					hpet_msi_disable;
+
 #ifdef CONFIG_PCI_MSI
 static unsigned long			hpet_num_timers;
 #endif
@@ -596,6 +598,9 @@ static void hpet_msi_capability_lookup(unsigned int start_timer)
 	unsigned int num_timers_used = 0;
 	int i;
 
+	if (hpet_msi_disable)
+		return;
+
 	if (boot_cpu_has(X86_FEATURE_ARAT))
 		return;
 	id = hpet_readl(HPET_ID);
@@ -928,6 +933,9 @@ static __init int hpet_late_init(void)
 	hpet_reserve_platform_timers(hpet_readl(HPET_ID));
 	hpet_print_config();
 
+	if (hpet_msi_disable)
+		return 0;
+
 	if (boot_cpu_has(X86_FEATURE_ARAT))
 		return 0;
 

arch/x86/kernel/quirks.c

@@ -491,6 +491,19 @@ void force_hpet_resume(void)
 		break;
 	}
 }
+
+/*
+ * HPET MSI on some boards (ATI SB700/SB800) has side effect on
+ * floppy DMA. Disable HPET MSI on such platforms.
+ */
+static void force_disable_hpet_msi(struct pci_dev *unused)
+{
+	hpet_msi_disable = 1;
+}
+
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS,
+			 force_disable_hpet_msi);
+
 #endif
 
 #if defined(CONFIG_PCI) && defined(CONFIG_NUMA)