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authorFeng Tang <feng.tang@intel.com>2015-06-15 17:40:01 +0800
committerIngo Molnar <mingo@kernel.org>2015-06-18 10:57:38 +0200
commitb58d930750135d6c5b8e5aa084c0e9303c78c286 (patch)
treefd7aacf41b5fbc6e6d3c7ffae910aa2322450a9c /arch/x86/kernel
parent956079e081427fe0c929eb284ab7e39f9b8e2023 (diff)
x86/platform/intel/baytrail: Add comments about why we disabled HPET on Baytrail
This question has been asked many times, and finally I found the official document which explains the problem of HPET on Baytrail, that it will halt in deep idle states. Signed-off-by: Feng Tang <feng.tang@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: john.stultz@linaro.org Cc: len.brown@intel.com Cc: matthew.lee@intel.com Link: http://lkml.kernel.org/r/1434361201-31743-1-git-send-email-feng.tang@intel.com [ Prettified things a bit. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/early-quirks.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
index fe9f0b79a18b..5cb9a4d6f623 100644
--- a/arch/x86/kernel/early-quirks.c
+++ b/arch/x86/kernel/early-quirks.c
@@ -627,8 +627,12 @@ static struct chipset early_qrk[] __initdata = {
{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, PCI_CLASS_DISPLAY_VGA, PCI_ANY_ID,
QFLAG_APPLY_ONCE, intel_graphics_stolen },
/*
- * HPET on current version of Baytrail platform has accuracy
- * problems, disable it for now:
+ * HPET on the current version of the Baytrail platform has accuracy
+ * problems: it will halt in deep idle state - so we disable it.
+ *
+ * More details can be found in section 18.10.1.3 of the datasheet:
+ *
+ * http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/atom-z8000-datasheet-vol-1.pdf
*/
{ PCI_VENDOR_ID_INTEL, 0x0f00,
PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet},