From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@lst.de (Christoph Hellwig) Date: Tue, 14 May 2019 08:11:41 +0200 Subject: [PATCH] nvme/pci: Use host managed power state for suspend In-Reply-To: References: <20190510212937.11661-1-keith.busch@intel.com> <0080aaff18e5445dabca509d4113eca8@AUSX13MPC105.AMER.DELL.COM> <955722d8fc16425dbba0698c4806f8fd@AUSX13MPC105.AMER.DELL.COM> <20190513143754.GE15318@localhost.localdomain> <7ab8274ef1ce46fcae54a50abc76ae4a@AUSX13MPC105.AMER.DELL.COM> <20190513145708.GA25897@lst.de> Message-ID: <20190514061141.GA7059@lst.de> On Mon, May 13, 2019@06:01:39PM +0000, Mario.Limonciello@dell.com wrote: > When using HMB the SSD will be writing to some memory mapped region. > Writing to > that region would use DMA to access host memory, no? Memory mapped region? It will use the devices DMA engine to write host memory, which we explicitly allowed it. > If the DMA controller is not functional writing to that region won't work properly as > it can't access that memory. The DMA controller is in the device. External DMA controllers are only used on very low-end periphals, usually cheap IP blocks like SPI controllers or similar. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] nvme/pci: Use host managed power state for suspend Date: Tue, 14 May 2019 08:11:41 +0200 Message-ID: <20190514061141.GA7059@lst.de> References: <20190510212937.11661-1-keith.busch@intel.com> <0080aaff18e5445dabca509d4113eca8@AUSX13MPC105.AMER.DELL.COM> <955722d8fc16425dbba0698c4806f8fd@AUSX13MPC105.AMER.DELL.COM> <20190513143754.GE15318@localhost.localdomain> <7ab8274ef1ce46fcae54a50abc76ae4a@AUSX13MPC105.AMER.DELL.COM> <20190513145708.GA25897@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mario.Limonciello@dell.com Cc: hch@lst.de, kbusch@kernel.org, keith.busch@intel.com, sagi@grimberg.me, linux-nvme@lists.infradead.org, rafael@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, kai.heng.feng@canonical.com List-Id: linux-pm@vger.kernel.org On Mon, May 13, 2019 at 06:01:39PM +0000, Mario.Limonciello@dell.com wrote: > When using HMB the SSD will be writing to some memory mapped region. > Writing to > that region would use DMA to access host memory, no? Memory mapped region? It will use the devices DMA engine to write host memory, which we explicitly allowed it. > If the DMA controller is not functional writing to that region won't work properly as > it can't access that memory. The DMA controller is in the device. External DMA controllers are only used on very low-end periphals, usually cheap IP blocks like SPI controllers or similar.