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authorWilly Tarreau <w@1wt.eu>2008-01-30 13:33:33 +0100
committerIngo Molnar <mingo@elte.hu>2008-01-30 13:33:33 +0100
commite6c4dc6c36b01d33a2e0c8a89828d8dd44fb4c1b (patch)
treecae199356ef2a55876ad1ffec0729738e838270c
parent45078cb5e2fb5a0e55c373755ed45b43d901f9e4 (diff)
x86: GEODE add the "mfgptfix" boot time option to fix MFGPT timers
The new "mfgptfix" boot command line option may be usd to fix MFGPT timers on AMD Geode platforms when the BIOS has incorrectly applied a workaround. TinyBIOS version 0.98 is known to be affected, 0.99 fixes the problem by letting the user disable the workaround. Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--Documentation/kernel-parameters.txt5
-rw-r--r--arch/x86/kernel/mfgpt_32.c15
2 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fe3031d5643..5d171b7b839 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1092,6 +1092,11 @@ and is between 256 and 4096 characters. It is defined in the file
Multi-Function General Purpose Timers on AMD Geode
platforms.
+ mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
+ the BIOS has incorrectly applied a workaround. TinyBIOS
+ version 0.98 is known to be affected, 0.99 fixes the
+ problem by letting the user disable the workaround.
+
mga= [HW,DRM]
mousedev.tap_time=
diff --git a/arch/x86/kernel/mfgpt_32.c b/arch/x86/kernel/mfgpt_32.c
index 3960ab7e149..219f86eb612 100644
--- a/arch/x86/kernel/mfgpt_32.c
+++ b/arch/x86/kernel/mfgpt_32.c
@@ -63,6 +63,21 @@ static int __init mfgpt_disable(char *s)
}
__setup("nomfgpt", mfgpt_disable);
+/* Reset the MFGPT timers. This is required by some broken BIOSes which already
+ * do the same and leave the system in an unstable state. TinyBIOS 0.98 is
+ * affected at least (0.99 is OK with MFGPT workaround left to off).
+ */
+static int __init mfgpt_fix(char *s)
+{
+ u32 val, dummy;
+
+ /* The following udocumented bit resets the MFGPT timers */
+ val = 0xFF; dummy = 0;
+ wrmsr(0x5140002B, val, dummy);
+ return 1;
+}
+__setup("mfgptfix", mfgpt_fix);
+
/*
* Check whether any MFGPTs are available for the kernel to use. In most
* cases, firmware that uses AMD's VSA code will claim all timers during