From patchwork Fri Sep 2 15:54:44 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 9311277 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2EFE760756 for ; Fri, 2 Sep 2016 15:55:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 20A572977A for ; Fri, 2 Sep 2016 15:55:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 153D3297D1; Fri, 2 Sep 2016 15:55:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BA5042977A for ; Fri, 2 Sep 2016 15:55:16 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bfqoG-0006lb-Dv; Fri, 02 Sep 2016 15:55:16 +0000 Received: from casper.infradead.org ([85.118.1.10]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bfqoE-0006e5-LS for linux-rockchip@bombadil.infradead.org; Fri, 02 Sep 2016 15:55:14 +0000 Received: from mail.kernel.org ([198.145.29.136]) by casper.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bfqoC-0001bG-Eg for linux-rockchip@lists.infradead.org; Fri, 02 Sep 2016 15:55:13 +0000 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0ED4D203A4; Fri, 2 Sep 2016 15:54:48 +0000 (UTC) Received: from localhost (173-27-161-33.client.mchsi.com [173.27.161.33]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A7B2C20340; Fri, 2 Sep 2016 15:54:46 +0000 (UTC) Subject: [PATCH v2 06/15] Add comment about why 32-bit read/modify/write isn't safe. To: Shawn Lin From: Bjorn Helgaas Date: Fri, 02 Sep 2016 10:54:44 -0500 Message-ID: <20160902155444.8650.28870.stgit@bhelgaas-glaptop2.roam.corp.google.com> In-Reply-To: <20160902154501.8650.99790.stgit@bhelgaas-glaptop2.roam.corp.google.com> References: <20160902154501.8650.99790.stgit@bhelgaas-glaptop2.roam.corp.google.com> User-Agent: StGit/0.16 MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160902_165512_627018_88F1F54E X-CRM114-Status: GOOD ( 11.56 ) X-BeenThere: linux-rockchip@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Upstream kernel work for Rockchip platforms List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, Brian Norris , Heiko Stuebner , Arnd Bergmann , Marc Zyngier , linux-pci@vger.kernel.org, Wenrui Li , linux-kernel@vger.kernel.org, Doug Anderson , linux-rockchip@lists.infradead.org, Rob Herring , Guenter Roeck Sender: "Linux-rockchip" Errors-To: linux-rockchip-bounces+patchwork-linux-rockchip=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP --- drivers/pci/host/pcie-rockchip.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c index ea75f35..c0c3ad5 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);