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x86/platform: Fix Geode LX timekeeping in the generic x86 build

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In 2007, commit 07190a08ee ("Mark TSC on GeodeLX reliable")
bypassed verification of the TSC on Geode LX. However, this code
(now in the check_system_tsc_reliable() function in
arch/x86/kernel/tsc.c) was only present if CONFIG_MGEODE_LX was
set.

OpenWRT has recently started building its generic Geode target
for Geode GX, not LX, to include support for additional
platforms. This broke the timekeeping on LX-based devices,
because the TSC wasn't marked as reliable:
https://dev.openwrt.org/ticket/20531

By adding a runtime check on is_geode_lx(), we can also include
the fix if CONFIG_MGEODEGX1 or CONFIG_X86_GENERIC are set, thus
fixing the problem.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: Andres Salomon <dilinger@queued.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marcelo Tosatti <marcelo@kvack.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1442409003.131189.87.camel@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
David Woodhouse 2015-09-16 14:10:03 +01:00 committed by Ingo Molnar
parent 5d7c631d92
commit 03da3ff1cf
1 changed files with 10 additions and 7 deletions
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5
arch/x86/kernel/tsc.c
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@ -21,6 +21,7 @@
#include <asm/hypervisor.h>
#include <asm/nmi.h>
#include <asm/x86_init.h>
#include <asm/geode.h>
unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
@ -1015,7 +1016,8 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable);
static void __init check_system_tsc_reliable(void)
{
#ifdef CONFIG_MGEODE_LX
#if defined(CONFIG_MGEODEGX1) || defined(CONFIG_MGEODE_LX) || defined(CONFIG_X86_GENERIC)
if (is_geode_lx()) {
/* RTSC counts during suspend */
#define RTSC_SUSP 0x100
unsigned long res_low, res_high;
@ -1024,6 +1026,7 @@ static void __init check_system_tsc_reliable(void)
/* Geode_LX - the OLPC CPU has a very reliable TSC */
if (res_low & RTSC_SUSP)
tsc_clocksource_reliable = 1;
}
#endif
if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
tsc_clocksource_reliable = 1;