From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anssi Hannula Subject: Re: Radeon unconnected HDMI eats samples at 280 kHz Date: Thu, 18 Sep 2014 00:26:54 +0300 Message-ID: <5419FC9E.9010302@iki.fi> References: <54198F38.30002@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from webmail.tpnet.fi (webmail.tpnet.fi [62.106.63.33]) by alsa0.perex.cz (Postfix) with ESMTP id 21931265452 for ; Wed, 17 Sep 2014 23:26:56 +0200 (CEST) In-Reply-To: <54198F38.30002@canonical.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: David Henningsson Cc: Alex Deucher , "alsa-devel@alsa-project.org" List-Id: alsa-devel@alsa-project.org 17.09.2014, 16:40, David Henningsson kirjoitti: > Hi, Hi, > While investigating some interesting debug output from PulseAudio, I > tried to figure out the cause. > > From what I can tell, my Radeon seems to ask for new samples at a very > high rate, which I estimate to be around 280 kHz. My radeon card has > DVI, HDMI and VGA connectors, and the only thing connected is my screen > over DVI. > > I'm currently running the 3.13 kernel with updated hda directory from > Takashi's tree, but I think it's been this way for a long time. > > Note that if a screen is connected to the HDMI card, the problem > disappears and sample rates are normal. > In short, do you think this is a driver bug, or just something we have > to live with as some sort of hw anomaly? > Since nothing is connected, it does not really hurt, except PulseAudio > gets confused (in a way that could potentially cause problems for > low-latency output, should something be connected later on). Not sure. IIRC, unlike the other gpus, on radeon the video driver needs to "manually" set sample rate dividers/etc based on the pixel clock rate, so I guess this might mean we can't have a proper audio clock without enabled video... Alex, any thoughts/info? If this is the case, it would probably be best if we prevented opening the device when output is not active (unless this causes some other issues), but I guess there is currently no easy way for the _audio_ driver to know that... > For reference, here's lspci of the HDMI card: > > 01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. > [AMD/ATI] RV710 [Radeon HD 4550] [1002:9540] (prog-if 00 [VGA controller]) > Subsystem: PC Partner Limited / Sapphire Technology Device [174b:e106] > 01:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] > RV710/730 HDMI Audio [Radeon HD 4000 series] [1002:aa38] > Subsystem: PC Partner Limited / Sapphire Technology Device [174b:aa38] > > -- Anssi Hannula