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>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ba6e65884603..ad80a1c718c6 100644
--- a/arch/x86/kernel/hpet.c
+++ b/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;