From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH] ARM:SAMSUNG: Move S3C DMA driver to drivers/dma Date: Wed, 8 Jun 2011 09:55:27 +0100 Message-ID: <20110608085526.GA2828@opensource.wolfsonmicro.com> References: <1307432901-22781-1-git-send-email-alim.akhtar@samsung.com> <20110607081527.GB20929@n2100.arm.linux.org.uk> <20110607182923.GA28451@n2100.arm.linux.org.uk> <20110607184329.GA20849@sirena.org.uk> <20110607214151.GA7712@opensource.wolfsonmicro.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from opensource.wolfsonmicro.com ([80.75.67.52]:32945 "EHLO opensource2.wolfsonmicro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754523Ab1FHIz3 (ORCPT ); Wed, 8 Jun 2011 04:55:29 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-samsung-soc-owner@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org To: Jassi Brar Cc: Russell King - ARM Linux , linux-samsung-soc@vger.kernel.org, Kyungmin Park , Jassi Brar , kgene.kim@samsung.com, root , linux-arm-kernel@lists.infradead.org On Wed, Jun 08, 2011 at 08:21:08AM +0530, Jassi Brar wrote: > On Wed, Jun 8, 2011 at 3:11 AM, Mark Brown > > That's fairly unusual, though - usually DMA controllers seem to support > > chaining requests before they support circular operation, at which point > > unless the hardware is badly misdone you can just chain another buffer, > > giving that buffer's worth of time for the CPU to respond. > While writing PL330 driver, I wasn't able to figure out a way to implement LLI. > Please have a look at the PL330 trm and suggest if we can implement it in a > generic way without considering them special requests. > I know pl080 supports LLI and it's fine. I'm perfectly prepared to believe that there's poorly designed hardware out there (either due to just poor design or deploying a controller in an inappropriate application) that requires us to do things in software; it's just relatively unusual as users tend to run into issues which either can't be resolved or are excessively painful to resolve. From mboxrd@z Thu Jan 1 00:00:00 1970 From: broonie@opensource.wolfsonmicro.com (Mark Brown) Date: Wed, 8 Jun 2011 09:55:27 +0100 Subject: [PATCH] ARM:SAMSUNG: Move S3C DMA driver to drivers/dma In-Reply-To: References: <1307432901-22781-1-git-send-email-alim.akhtar@samsung.com> <20110607081527.GB20929@n2100.arm.linux.org.uk> <20110607182923.GA28451@n2100.arm.linux.org.uk> <20110607184329.GA20849@sirena.org.uk> <20110607214151.GA7712@opensource.wolfsonmicro.com> Message-ID: <20110608085526.GA2828@opensource.wolfsonmicro.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jun 08, 2011 at 08:21:08AM +0530, Jassi Brar wrote: > On Wed, Jun 8, 2011 at 3:11 AM, Mark Brown > > That's fairly unusual, though - usually DMA controllers seem to support > > chaining requests before they support circular operation, at which point > > unless the hardware is badly misdone you can just chain another buffer, > > giving that buffer's worth of time for the CPU to respond. > While writing PL330 driver, I wasn't able to figure out a way to implement LLI. > Please have a look at the PL330 trm and suggest if we can implement it in a > generic way without considering them special requests. > I know pl080 supports LLI and it's fine. I'm perfectly prepared to believe that there's poorly designed hardware out there (either due to just poor design or deploying a controller in an inappropriate application) that requires us to do things in software; it's just relatively unusual as users tend to run into issues which either can't be resolved or are excessively painful to resolve.