From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH_TYPE for OMAP1 Date: Sat, 24 Nov 2018 17:11:31 -0800 Message-ID: <20181125011131.GK53235@atomide.com> References: <20181119104040.12885-1-peter.ujfalusi@ti.com> <20181119184649.GE16897@darkstar.musicnaut.iki.fi> <6af8c6e7-bf5c-5555-161b-5d3fb7ecae43@ti.com> <20181120210406.GB24888@darkstar.musicnaut.iki.fi> <20181122102948.GN6920@n2100.armlinux.org.uk> <20181122151236.GA9611@n2100.armlinux.org.uk> <6ed280af-edb6-4be7-82f4-7fc00378103e@ti.com> <20181123185215.GH12912@darkstar.musicnaut.iki.fi> <20181124200942.GS6920@n2100.armlinux.org.uk> <20181125010717.GJ53235@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181125010717.GJ53235@atomide.com> Sender: linux-kernel-owner@vger.kernel.org To: Russell King - ARM Linux Cc: Aaro Koskinen , Peter Ujfalusi , vkoul@kernel.org, dan.j.williams@intel.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org List-Id: linux-omap@vger.kernel.org * Tony Lindgren [181125 01:07]: > * Russell King - ARM Linux [181124 20:10]: > > On Fri, Nov 23, 2018 at 08:52:15PM +0200, Aaro Koskinen wrote: > > > Hi, > > > > > > On Fri, Nov 23, 2018 at 02:35:04PM +0200, Peter Ujfalusi wrote: > > > > On 22/11/2018 17.12, Russell King - ARM Linux wrote: > > > > > I'm also not sure about this: > > > > > > > > > > if (cpu_is_omap15xx()) > > > > > end++; > > > > > > > > > > in dma_dest_len() - is that missing from the omap-dma driver? It looks > > > > > like a work-around for some problem on OMAP15xx, but I can't make sense > > > > > about why it's in the UDC driver rather than the legacy DMA driver. > > > > > > > > afaik no other legacy drivers were doing similar thing, this must be > > > > something which is needed for the omap_udc driver to fix up something? > > > > > > Here's the patch that added it: https://marc.info/?l=linux-omap&m=119634396324221&w=2 > > > > > > "Make DMA-OUT behave on the 1510 ... the 1510 CPC register was just > > > off-by-one with respect to the 1611 CDAC" > > > > ... which suggests that's a problem with the CPC register itself, and > > we should fix that in the DMAengine driver rather than the USB gadget > > driver. > > > > Tony, any input on this? > > Yeah that sounds like some hardware work-around for 15xx as described > in the DMA_DEST_LAST macro reading CSAC on 15xx instead of CDAC. Seems > like it should be done in the dmaengine driver.. My guess is that other > dma users never needed to read CSAC register? And it looks like for 15xx we have CPC and CSAC both at offset 0x18 in arch/arm/mach-omap1/dma.c, seems like the dma driver is missing handling for the CPC register that's there only for 15xx. Regards, Tony