From mboxrd@z Thu Jan 1 00:00:00 1970 From: vinod.koul@intel.com (Vinod Koul) Date: Tue, 9 Dec 2014 11:40:03 +0530 Subject: [PATCH] dmaengine: pl330: Set residue in tx_status callback In-Reply-To: <20141208142321.GE11285@n2100.arm.linux.org.uk> References: <1416995095-13763-1-git-send-email-padma.v@samsung.com> <547DF61D.3010909@metafoo.de> <20141205151843.GV11285@n2100.arm.linux.org.uk> <20141208130727.GK16827@intel.com> <20141208142321.GE11285@n2100.arm.linux.org.uk> Message-ID: <20141209061003.GX16827@intel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Dec 08, 2014 at 02:23:21PM +0000, Russell King - ARM Linux wrote: > On Mon, Dec 08, 2014 at 06:37:27PM +0530, Vinod Koul wrote: > > I actually like the split model, you can also prepare txn ahead of time and > > submit them when needed. > > Actually, you can't - that's not permitted. I have email(s) from Dan > explicitly stating that it is permitted for a driver to take a spinlock > in their prepare callback, and release it when the descriptor is > submitted. Several DMA engine drivers (particularly those in for > async_tx) do exactly that. > > The reason that submit is separate from prepare is to allow DMA engine > users to set a callback - if it weren't for that, there wouldn't be a > submit step, prepare would have done everything. Yes thats right. Do you mind pointing to thread Dan replied, I would like to add these bits and anything else missing to Documentation Thanks -- ~Vinod