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[94.29.41.50]) by smtp.googlemail.com with ESMTPSA id h17sm2479535ljj.118.2020.08.06.07.22.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Aug 2020 07:22:45 -0700 (PDT) Subject: Re: [Patch v2 2/4] dmaengine: tegra: Add Tegra GPC DMA driver To: Rajesh Gumasta , Laxman Dewangan , Jonathan Hunter , "vkoul@kernel.org" , "dan.j.williams@intel.com" , "thierry.reding@gmail.com" , "p.zabel@pengutronix.de" , "dmaengine@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" Cc: Krishna Yarlagadda , Pavan Kunapuli References: <1596699006-9934-1-git-send-email-rgumasta@nvidia.com> <1596699006-9934-3-git-send-email-rgumasta@nvidia.com> From: Dmitry Osipenko Message-ID: <8fa139f2-685e-9e19-df55-bc7f84ec9a4c@gmail.com> Date: Thu, 6 Aug 2020 17:22:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-tegra-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org 06.08.2020 16:56, Rajesh Gumasta пишет: ... >>> +static const struct __maybe_unused dev_pm_ops >> tegra_dma_dev_pm_ops = { >>> + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(tegra_dma_pm_suspend, >>> +tegra_dma_pm_resume) }; >> >> Please explain why this is needed. All DMA should be stopped (not >> paused) on system's suspend, shouldn't it? > I have rechecked with HW verification team and they confirmed that after suspend, csr and channel registers will get reset hence on resume we need to restore back. > Also GPCDMA does not support power gate as a unit. But all registers are re-programmed on starting a DMA transfer, hence why do you need to save-restore them on suspend-resume?