From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082Ab3J0Mze (ORCPT ); Sun, 27 Oct 2013 08:55:34 -0400 Received: from mout.gmx.net ([212.227.17.22]:54891 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753161Ab3J0Mzc (ORCPT ); Sun, 27 Oct 2013 08:55:32 -0400 From: Andreas Werner To: tglx@linutronix.de Cc: mingo@redhat.com, hpa@zytor.com, x86@kernel.org, dave@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, wernerandy@gmx.de Subject: [PATCH] X86: MM: Add PAT Type write-through in combination with mtrr Date: Sun, 27 Oct 2013 13:55:25 +0100 Message-Id: <1382878525-3410-1-git-send-email-wernerandy@gmx.de> X-Mailer: git-send-email 1.8.4 X-Provags-ID: V03:K0:UWU8ETfk5NJf6LCIu7TtMKKnZMqmJr7LtJhYcMH+c/dMVqIZ0F3 iVvfYh6I7RqrXoUT7Rn/GmzaL/kkjSRY+PSeDC/xc5e0Ci9z9QN6YjYNIJyq9/imzlbNJ8o WknskP4ReepBzi3wn30b6E+1a02KMGyav/EEYfx35eO2rZAXIidp27RdtjpOW9Y6MHExUoS 6FDY9JIa0PColiVXIVtkA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch adds the Write-through memory type in combination with mtrr. If you call ioremap_cache to request cachable memory (write-back) the function tries to set the PAT to write-back only if the mtrr setting of the requested region is also marked as Write-Back. If the mttr regions are marked e.g. as Write-through or with other types, the function will always return UC- memory. If you check the Intel document " IA-32 SDM vol 3a table Effective Memory Type", there are many other combinations possible. This patch will only add the following combination: PAT=Write-Back + MTRR=Write-Through = Effective Memory of Write-Through Tested on - Intel (R) Atom E680 (Tunnel Creek) - Intel (R) Core(TM)2 Duo Signed-off-by: Andreas Werner --- arch/x86/mm/pat.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 6574388..9cfe107 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -149,10 +149,15 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type) u8 mtrr_type; mtrr_type = mtrr_type_lookup(start, end); - if (mtrr_type != MTRR_TYPE_WRBACK) - return _PAGE_CACHE_UC_MINUS; - return _PAGE_CACHE_WB; + switch (mtrr_type) { + case MTRR_TYPE_WRBACK: + case MTRR_TYPE_WRTHROUGH: + return _PAGE_CACHE_WB; + + default: + return _PAGE_CACHE_UC_MINUS; + } } return req_type; -- 1.8.4