linux-kernel - RE: [alsa-devel] [PATCH 1/6] hda_intel: Add Lynx Point HD Audio Controller DeviceIDs

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Date:	Wed, 8 Feb 2012 00:35:33 +0000
From:	"Heasley, Seth" <seth.heasley@...el.com>
To:	David Henningsson <david.henningsson@...onical.com>
CC:	Takashi Iwai <tiwai@...e.de>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"perex@...ex.cz" <perex@...ex.cz>,
	"Ralston, James D" <james.d.ralston@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [alsa-devel] [PATCH 1/6] hda_intel: Add Lynx Point HD Audio
 Controller DeviceIDs

>> I'm also in favor of not rocking the boat, but I'm curious what
>changing this would entail, and what would be the advantage or rationale
>for making the change?
>
>Reading the LPIB register, and reading the DMA position buffer, are two
>different methods of reading the current playback (or recording)
>position, i e which sample is currently being played back.
>
>The problem is that some chipsets prefer one method over the other, i e,
>only one of the methods work reliably. And if the other method only
>breaks occasionally, this can be quite difficult to detect and track
>down - we will have users complaining about their audio sometimes either
>sounding distorted, maybe not working at all, or just once in a while
>glitches. All of these symptoms can have many causes, so deducing that
>to a broken playback position is time consuming. That's why I think it's
>worth the extra question, to get it right from the start.
>
>So...thanks in advance for looking it up for us? :-)

I'm inquiring about it, but I can say that it seems to work just fine using the DMA position buffer.

-Seth


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