Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932123AbbBTNzM (ORCPT ); Fri, 20 Feb 2015 08:55:12 -0500 Received: from mail-wg0-f49.google.com ([74.125.82.49]:35999 "EHLO mail-wg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754041AbbBTNyL (ORCPT ); Fri, 20 Feb 2015 08:54:11 -0500 MIME-Version: 1.0 In-Reply-To: <54E6DF09.9060505@gmail.com> References: <1424365606-19964-1-git-send-email-dinguyen@opensource.altera.com> <1424365606-19964-2-git-send-email-dinguyen@opensource.altera.com> <54E6DF09.9060505@gmail.com> From: Rob Herring Date: Fri, 20 Feb 2015 07:53:50 -0600 Message-ID: Subject: Re: [RESEND PATCH 2/2] arm: socfpga: Set share override bit of the l2 cache controller To: Dinh Nguyen Cc: Dinh Nguyen , Russell King - ARM Linux , Arnd Bergmann , "linux-kernel@vger.kernel.org" , Olof Johansson , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1465 Lines: 35 On Fri, Feb 20, 2015 at 1:15 AM, Dinh Nguyen wrote: > Hi Rob, > > On 2/19/15 12:13 PM, Rob Herring wrote: >> On Thu, Feb 19, 2015 at 11:06 AM, wrote: >>> From: Dinh Nguyen >>> >>> By not having bit 22 set in the PL310 Auxiliary Control register (shared >>> attribute override enable) has the side effect of transforming Normal >>> Shared Non-cacheable reads into Cacheable no-allocate reads. >>> >>> Coherent DMA buffers in Linux always have a Cacheable alias via the >>> kernel linear mapping and the processor can speculatively load cache >>> lines into the PL310 controller. With bit 22 cleared, Non-cacheable >>> reads would unexpectedly hit such cache lines leading to buffer >>> corruption. >> >> You really should be doing this in your bootloader. >> > > Can I ask what is your reasoning for doing this in the bootloader? It's > seems like this is such a nice mechanism to do it here. Primarily, this register is secure only and we try to avoid secure mode setup in the kernel. Russell also has had a patch to do this generically in his patch queue forever. If we want this in the kernel, then we should apply that. Rob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/