From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754212AbbFOJqN (ORCPT ); Mon, 15 Jun 2015 05:46:13 -0400 Received: from mga09.intel.com ([134.134.136.24]:43085 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753953AbbFOJqE (ORCPT ); Mon, 15 Jun 2015 05:46:04 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,618,1427785200"; d="scan'208";a="587967745" From: Feng Tang To: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , linux-kernel@vger.kernel.org, len.brown@intel.com, john.stultz@linaro.org Cc: matthew.lee@intel.com, Feng Tang Subject: [PATCH] x86/intel: Add comments about why we disabled HPET on Baytrail Date: Mon, 15 Jun 2015 17:40:01 +0800 Message-Id: <1434361201-31743-1-git-send-email-feng.tang@intel.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The 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 --- arch/x86/kernel/early-quirks.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c index fe9f0b7..9cdc6acb 100644 --- a/arch/x86/kernel/early-quirks.c +++ b/arch/x86/kernel/early-quirks.c @@ -628,7 +628,10 @@ static struct chipset early_qrk[] __initdata = { QFLAG_APPLY_ONCE, intel_graphics_stolen }, /* * HPET on current version of Baytrail platform has accuracy - * problems, disable it for now: + * problems, that it will halt in deep idle state, so disable it. + * + * Please refer section 18.10.1.3 of http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/atom-z8000-datasheet-vol-1.pdf + * for more details. */ { PCI_VENDOR_ID_INTEL, 0x0f00, PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet}, -- 1.7.9.5