From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65F7EC35280 for ; Mon, 30 Sep 2019 10:56:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4778121855 for ; Mon, 30 Sep 2019 10:56:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730882AbfI3K42 (ORCPT ); Mon, 30 Sep 2019 06:56:28 -0400 Received: from mga09.intel.com ([134.134.136.24]:51423 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730705AbfI3K42 (ORCPT ); Mon, 30 Sep 2019 06:56:28 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Sep 2019 03:56:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,565,1559545200"; d="scan'208";a="204804555" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga001.fm.intel.com with SMTP; 30 Sep 2019 03:56:24 -0700 Received: by lahna (sSMTP sendmail emulation); Mon, 30 Sep 2019 13:56:23 +0300 Date: Mon, 30 Sep 2019 13:56:23 +0300 From: Mika Westerberg To: Tuowen Zhao Cc: lee.jones@linaro.org, linux-kernel@vger.kernel.org, andriy.shevchenko@linux.intel.com, acelan.kao@canonical.com, bhelgaas@google.com, kai.heng.feng@canonical.com Subject: Re: [PATCH] mfd: intel-lpss: use devm_ioremap_uc for mmio Message-ID: <20190930105623.GU2714@lahna.fi.intel.com> References: <20190927175513.31054-1-ztuowen@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190927175513.31054-1-ztuowen@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, In $subject, use MMIO instead of mmio. On Fri, Sep 27, 2019 at 11:55:13AM -0600, Tuowen Zhao wrote: > Write-combining BAR for intel-lpss-pci in MTRR causes system hangs > during boot. > > This patch adds devm_ioremap_uc as a new managed wrapper to ioremap_uc > and with it forces the use of strongly uncachable mmio in intel-lpss. > > This bahavior is seen on Dell XPS 13 7390 2-in-1: > > [ 0.001734] 5 base 4000000000 mask 6000000000 write-combining I think it is worth mentioning that this is actually a BIOS bug and fixed by some vendors via BIOS upgrade. > 4000000000-7fffffffff : PCI Bus 0000:00 > 4000000000-400fffffff : 0000:00:02.0 (i915) > 4010000000-4010000fff : 0000:00:15.0 (intel-lpss-pci) > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=203485 > Signed-off-by: Tuowen Zhao > --- > drivers/mfd/intel-lpss.c | 2 +- > include/linux/io.h | 2 ++ > lib/devres.c | 19 +++++++++++++++++++ > 3 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c > index 277f48f1cc1c..06106c9320bb 100644 > --- a/drivers/mfd/intel-lpss.c > +++ b/drivers/mfd/intel-lpss.c > @@ -395,7 +395,7 @@ int intel_lpss_probe(struct device *dev, > if (!lpss) > return -ENOMEM; > > - lpss->priv = devm_ioremap(dev, info->mem->start + LPSS_PRIV_OFFSET, > + lpss->priv = devm_ioremap_uc(dev, info->mem->start + LPSS_PRIV_OFFSET, > LPSS_PRIV_SIZE); Can you add a comment here explaining why this particular driver needs to use _uc version? Normally drivers call the plain devm_ioremap() and expect to get non-cached memory, however ioremap() (which resolves to ioremap_nocache()) does not touch x86 PAT configuration which is the reason we need to call _uc variant here. Otherwise looks good to me.