Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754747AbbFEN7r (ORCPT ); Fri, 5 Jun 2015 09:59:47 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59789 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161044AbbFEN7e (ORCPT ); Fri, 5 Jun 2015 09:59:34 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Thomas Petazzoni , Jason Cooper , =?UTF-8?q?Bj=C3=B8rn=20Mork?= , Luis Henriques Subject: [PATCH 3.16.y-ckt 059/110] ARM: mvebu: do not register custom DMA operations when coherency is disabled Date: Fri, 5 Jun 2015 14:57:42 +0100 Message-Id: <1433512713-22984-60-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1433512713-22984-1-git-send-email-luis.henriques@canonical.com> References: <1433512713-22984-1-git-send-email-luis.henriques@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2503 Lines: 63 3.16.7-ckt13 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Petazzoni 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: Jason Cooper Cc: Bjørn Mork Signed-off-by: Luis Henriques --- 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 2ffccd4eb084..01efe130912e 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; } -- 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/