From mboxrd@z Thu Jan 1 00:00:00 1970 From: viresh kumar Subject: Re: [PATCH V2 6/6] spi/spi-pl022: Request/free DMA channels as and when required. Date: Wed, 10 Aug 2011 14:59:31 +0530 Message-ID: <4E424F7B.2000800@st.com> References: <566c0525199f498f04422d4c3b2ddd7466648c20.1312965742.git.viresh.kumar@st.com> <20110810090042.GE1831@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Pratyush ANAND , Rajeev KUMAR , Bhavna YADAV , Bhupesh SHARMA , Armando VISCONTI , "linus.walleij@linaro.org" , "jassisinghbrar@gmail.com" , Vipin KUMAR , "grant.likely@secretlab.ca" , Shiraz HASHIM , Amit VIRDI , Vipul Kumar SAMAR , "viresh.linux@gmail.com" , Deepak SIKRI , "spi-devel-general@lists.sourceforge.net" , "linux-arm-kernel@lists.infradead.org" To: Russell King - ARM Linux , Dan Williams , "Koul, Vinod" Return-path: In-Reply-To: <20110810090042.GE1831@n2100.arm.linux.org.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: linux-spi.vger.kernel.org On 08/10/2011 02:30 PM, Russell King - ARM Linux wrote: >> > They must be allocated when they are required and must be freed after we are >> > done with transfers. So that they can be used by other users. > Which DMA engine driver requires this? > dw_dmac.c > Normally, when we have DMA engine drivers with multiple request signals, > the slave peripheral side publishes several virtual channels which are > claimed by the peripheral drivers. This (amongst other things) allows > the peripheral drivers to hold claim to one of the virtual channels > all the time that it's required. If users of DMA expect DMA engine drivers to work this way, then we should have this mentioned clearly in DMA slave documentation. @Dan/Vinod: What do you say? -- viresh