Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752292AbdI1OGK (ORCPT ); Thu, 28 Sep 2017 10:06:10 -0400 Received: from mail-wr0-f179.google.com ([209.85.128.179]:53787 "EHLO mail-wr0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750759AbdI1OGI (ORCPT ); Thu, 28 Sep 2017 10:06:08 -0400 X-Google-Smtp-Source: AOwi7QAz3Qvm4mqAxn2kBpl4/OizIBLTikVQIsUbmMZtUKmh8e2fQBq/ObFw7L9q8fNZuIvPJyYB1g== Subject: Re: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller To: Vinod Koul Cc: Thierry Reding , Jonathan Hunter , Laxman Dewangan , Peter De Schrijver , Prashant Gaikwad , Michael Turquette , Stephen Boyd , Rob Herring , linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, dmaengine@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org References: <0a45e058baba72124b91c663ce1d908d275f4044.1506380746.git.digetx@gmail.com> <20170928092949.GB30097@localhost> From: Dmitry Osipenko Message-ID: Date: Thu, 28 Sep 2017 17:06:03 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20170928092949.GB30097@localhost> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 785 Lines: 25 On 28.09.2017 12:29, Vinod Koul wrote: >> + default: >> + return -EINVAL; >> + } >> + >> + ahb_seq = burst << TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT; >> + ahb_seq |= TEGRA_AHBDMA_CHANNEL_ADDR_WRAP; >> + ahb_seq |= TEGRA_AHBDMA_CHANNEL_INTR_ENB; >> + >> + writel_relaxed(ahb_seq, >> + ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_SEQ); >> + >> + writel_relaxed(ahb_addr, >> + ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_PTR); > > oh no, you don't write to HW here. This can be called anytime when you have > txn running! You should save these and use them in prep_ calls. > BTW, some of the DMA drivers have exactly the same problem. I now see that it is actually documented explicitly in provider.txt, but that's inconsistent across the actual drivers. -- Dmitry