From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from youngberry.canonical.com ([91.189.89.112]:46841 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751949AbbE1KuT (ORCPT ); Thu, 28 May 2015 06:50:19 -0400 Date: Thu, 28 May 2015 11:50:04 +0100 From: Luis Henriques To: =?iso-8859-1?Q?Bj=F8rn?= Mork Cc: Sasha Levin , Jason Cooper , Andrew Lunn , Sebastian Hesselbarth , Gregory Clement , Ezequiel Garcia , linux-arm-kernel@lists.infradead.org, Thomas Petazzoni , Imre Kaloz , stable@vger.kernel.org Subject: Re: [RESEND PATCH 3.18-stable v2] ARM: mvebu: do not register custom DMA operations when coherency is disabled Message-ID: <20150528105004.GC2437@ares> References: <1432117387-22435-1-git-send-email-bjorn@mork.no> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1432117387-22435-1-git-send-email-bjorn@mork.no> Sender: stable-owner@vger.kernel.org List-ID: On Wed, May 20, 2015 at 12:23:07PM +0200, Bj�rn Mork wrote: > Hello Sasha! > > This backported mvebu fix seems to have slipped through the cracks by > accident. IIUC, the OpenWRT mvebu maintainer(s) are particularily > interested in having this bug fixed for 3.18-stable. See this thread > for the original patch submission and discussion: > http://permalink.gmane.org/gmane.linux.kernel.stable/127243 > Thank you, I'm also queuing this patch for the 3.16 kernel as you tagged it for v3.16..v3.18. Cheers, -- Lu�s > I'm including the full patch below for convenicence. It still applies > to the current 3.18-stable tree (apply with "git am --scissors" if you > use this email as source). > > I hope Thomas, Imre or Andrew can fill in the details if more > background info is necessary... > > > Thanks, > Bj�rn > > ---- >8 ---- >8 ---- > From: Thomas Petazzoni > Subject: ARM: mvebu: do not register custom DMA operations when coherency is disabled > Date: Thu, 12 Mar 2015 11:58:12 +0100 > > This patch is a partial backport of commit ef01c6c36bb8 ("ARM: mvebu: > remove Armada 375 Z1 workaround for I/O coherency"). This commit was > merged in v3.19, so kernel versions later than v3.19 are not affected > by the problem that this commit fixes. > > It does not make a lot of sense to backport this commit entirely, > since it is mainly removing some no longer useful code. However, this > commit is also making sure that the bus_register_notifier that > register the custom DMA operations that should be used for HW I/O > coherency does not get registered when said HW I/O coherency is not > enabled. > > This is particularly critical since we have decided to disable HW I/O > coherency completely in all kernels < 4.0, to be on the safe side, > while experimenting a new implementation of the HW I/O coherency in >= > 4.0. > > Without this commit, kernels earlier than 3.18 have the custom DMA > operations normally used for HW I/O coherency registered (they don't > do cache maintenance operations), while HW I/O coherency is > disabled. It essentially causes every DMA transfer to transfer > garbage. > > The issue fixed by this commit was introduced by 5ab5afd8ba83 ("ARM: > mvebu: implement Armada 375 coherency workaround"), but it was not > visible until now since it didn't cause any problem when HW I/O > coherency is enabled. > > Signed-off-by: Thomas Petazzoni > Cc: v3.16..v3.18 > --- > arch/arm/mach-mvebu/coherency.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-mvebu/coherency.c b/arch/arm/mach-mvebu/coherency.c > index 2ffccd4..01efe13 100644 > --- a/arch/arm/mach-mvebu/coherency.c > +++ b/arch/arm/mach-mvebu/coherency.c > @@ -448,8 +448,9 @@ static int __init coherency_late_init(void) > armada_375_coherency_init_wa(); > } > > - bus_register_notifier(&platform_bus_type, > - &mvebu_hwcc_nb); > + if (coherency_available()) > + bus_register_notifier(&platform_bus_type, > + &mvebu_hwcc_nb); > > return 0; > } > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe stable" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html