linux-kernel - Re: [regression] 2.6.25-rc4 snd-es18xx broken on Alpha

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Date:	Sun, 9 Mar 2008 18:57:59 -0500 (CDT)
From:	rct@...s.com (Bob Tracy)
To:	Ivan Kokshaysky <ink@...assic.park.msu.ru>
CC:	Bob Tracy <rct@...s.com>, linux-kernel@...r.kernel.org,
	linux-alpha@...r.kernel.org
Subject: Re: [regression] 2.6.25-rc4 snd-es18xx broken on Alpha

Ivan Kokshaysky wrote:
> Sounds like a DMA screwup.

Agreed.  There's a comment line near the top of the es18xx.c that has
been there for a *long* time:

	Support for 16 bit DMA seems to be broken. I've no hardware
	to tune it.

Supposedly with the ES1888, dma1 is for capture, dma2 is for playback.
dma2 == 5 is a 16-bit channel, yes?  That could explain much...

As for the values "chosen" for dma1 and dma2, they are the ones that
keep showing up in the Alpha sound "howto" postings/documents.  The
driver can cope with dma1 == dma2 by enforcing half-duplex mode in
software, but the OSS "sb" driver works fine with the indicated DMA
channel values.  Besides, if the ES1888 is really capable of full-duplex
operation, a potential half-duplex workaround doesn't have much appeal.

> I wonder if it still works on x86 - perhaps you ought to ask ALSA folks.

I tried contacting the driver authors as indicated in the driver source
file.  Christian Fischbach seems to have disappeared.  Still waiting to
hear from Abramo Bagnara.

-- 
------------------------------------------------------------------------
Bob Tracy          |  "I was a beta tester for dirt.  They never did
rct@...s.com       |   get all the bugs out." - Steve McGrew on /.
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