From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller Date: Thu, 28 Sep 2017 17:35:59 +0300 Message-ID: <260fa409-0d07-ec9e-9e3b-fb08255026d8@gmail.com> References: <0a45e058baba72124b91c663ce1d908d275f4044.1506380746.git.digetx@gmail.com> <20170928092949.GB30097@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: devicetree@vger.kernel.org On 28.09.2017 17:06, Dmitry Osipenko wrote: > 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. > Also, shouldn't prep_ and dma_slave_config be protected with locking? I don't see DMA core doing any locking and seems none of the drivers too. -- Dmitry