From patchwork Thu Sep 1 16:44:43 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 664973 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3sQ7YC6yyTz9s3T for ; Fri, 2 Sep 2016 02:50:39 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755118AbcIAQow (ORCPT ); Thu, 1 Sep 2016 12:44:52 -0400 Received: from mail.kernel.org ([198.145.29.136]:56750 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754045AbcIAQos (ORCPT ); Thu, 1 Sep 2016 12:44:48 -0400 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 374FA20379; Thu, 1 Sep 2016 16:44:46 +0000 (UTC) Received: from localhost (unknown [69.71.1.1]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 23AE820272; Thu, 1 Sep 2016 16:44:45 +0000 (UTC) Subject: [PATCH 6/9] Add comment about why 32-bit read/modify/write isn't safe. To: Shawn Lin From: Bjorn Helgaas Cc: devicetree@vger.kernel.org, Wenrui Li , Heiko Stuebner , Arnd Bergmann , Marc Zyngier , linux-pci@vger.kernel.org, Brian Norris , linux-kernel@vger.kernel.org, Doug Anderson , linux-rockchip@lists.infradead.org, Rob Herring , Guenter Roeck Date: Thu, 01 Sep 2016 11:44:43 -0500 Message-ID: <20160901164443.14195.13483.stgit@bhelgaas-glaptop2.roam.corp.google.com> In-Reply-To: <20160901163758.14195.15725.stgit@bhelgaas-glaptop2.roam.corp.google.com> References: <20160901163758.14195.15725.stgit@bhelgaas-glaptop2.roam.corp.google.com> User-Agent: StGit/0.16 MIME-Version: 1.0 X-Spam-Status: No, score=-1.0 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, NML_ADSP_CUSTOM_MED,UNPARSEABLE_RELAY autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org --- drivers/pci/host/pcie-rockchip.c | 5 +++++ 1 file changed, 5 insertions(+) --- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c index 17612e5..33bf2e1 100644 --- a/drivers/pci/host/pcie-rockchip.c +++ b/drivers/pci/host/pcie-rockchip.c @@ -282,6 +282,11 @@ static int rockchip_pcie_wr_own_conf(struct rockchip_pcie *rockchip, mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8)); + /* + * N.B. This read/modify/write isn't safe in general because it can + * corrupt RW1C bits in adjacent registers. But the hardware + * doesn't support smaller writes. + */ tmp = readl(rockchip->apb_base + PCIE_RC_CONFIG_BASE + offset) & mask; tmp |= val << ((where & 0x3) * 8); writel(tmp, rockchip->apb_base + PCIE_RC_CONFIG_BASE + offset);