linux-kernel - Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH

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Message-ID: <20181124200942.GS6920@n2100.armlinux.org.uk>
Date:   Sat, 24 Nov 2018 20:09:42 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Aaro Koskinen <aaro.koskinen@....fi>, tony@...mide.com
Cc:     Peter Ujfalusi <peter.ujfalusi@...com>, vkoul@...nel.org,
        dan.j.williams@...el.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH_TYPE for OMAP1

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?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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