From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753196AbdASO57 (ORCPT ); Thu, 19 Jan 2017 09:57:59 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:33606 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752934AbdASO54 (ORCPT ); Thu, 19 Jan 2017 09:57:56 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 19 Jan 2017 20:27:43 +0530 From: Abhishek Sahu To: Andy Gross Cc: Vinod Koul , dan.j.williams@intel.com, stanimir.varbanov@linaro.org, mcgrof@suse.com, okaya@codeaurora.org, pramod.gurav@linaro.org, arnd@arndb.de, linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH 2/5] dmaengine: Add support for custom data mapping In-Reply-To: <20170119141317.GA9631@hector.attlocal.net> References: <20161219050642.GA3047@hector.attlocal.net> <20161219154923.GT25795@localhost> <20161219175210.GB3047@hector.attlocal.net> <20161220202511.GD3047@hector.attlocal.net> <61cb961a6f448cfc48b983329e329b34@codeaurora.org> <20161229175450.GB17770@hector.attlocal.net> <8055fa20b35139e7d13831583ebf4f4f@codeaurora.org> <20170102161233.GC17770@hector.attlocal.net> <20170119050150.GI3573@localhost> <20170119141317.GA9631@hector.attlocal.net> Message-ID: <5332b039ab52d2ef7353121615871757@codeaurora.org> User-Agent: Roundcube Webmail/1.2.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-01-19 19:43, Andy Gross wrote: > On Thu, Jan 19, 2017 at 10:31:50AM +0530, Vinod Koul wrote: > > > >> > > > >> > > >I really think that we need some additional API that allows for the flag >> > > >munging >> > > >for the descriptors instead of overriding the prep_slave_sg. We already >> > > >needed >> > > >to change the way the flags are passed anyway. And instead of building up >> > > >a >> > > >special sg list, the API should take a structure that has a 1:1 mapping of >> > > >the >> > > >flags to the descriptors. And you would call this API on your descriptor >> > > >before >> > > >issuing it. >> >> Munging wont be a good idea, but for some of the cases current flags >> can be >> used, and if need be, we can add additional flags > > Is adding flags a possibility? I tried to match up BAM flags to ones > that made > sense that were currently defined, but adding a CMD flag would be kind > of odd. > > It was kind of a stretch to use the PREP_FENCE for the notify when done > flag. > >> > > > >> > > >So build up the sglist. Call the prep_slave_sg. You get back a tx >> > > >descriptor >> > > >that underneath is a bam descriptor. Then call the API giving the >> > > >descriptor >> > > >and the structure that defines the flags for the descriptors. Then submit >> > > >the >> > > >descriptor. >> > > > >> > > >Something like: >> > > >int qcom_bam_apply_descriptor_flags(struct dma_async_tx_descriptor *tx, >> > > > u16 *flags) >> > > >{ >> > > > struct bam_async_desc async_desc = container_of(tx, >> > > > struct bam_async_desc, >> > > > vd.tx); >> > > > int i; >> > > > >> > > > for (i = 0; i < async_desc->num_desc; i++) >> > > > async_desc->desc[i].flags = cpu_to_le16(flags[i]); >> > > >} >> > > > >> > > >EXPORT_SYMBOL(qcom_bam_apply_descriptor_flags) >> >> This makes it bam specific and causes issues if we want to use this >> code in >> generic libs, but yes this is an option but should be last resort. > > If adding flags is a possibility (which it didn't seem to be in the > past), that > would make things much easier. Also, Main reason for this approach was to set different flags for each BAM descriptor present in a TX descriptor. > > Regards, > > Andy -- Abhishek Sahu