From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [PATCH 0/2] RFC: support for audio wall clock Date: Fri, 20 Jul 2012 14:57:38 -0500 Message-ID: <5009B832.5060802@linux.intel.com> References: <1340917955-31422-1-git-send-email-pierre-louis.bossart@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by alsa0.perex.cz (Postfix) with ESMTP id 8EA7626535F for ; Fri, 20 Jul 2012 21:57:38 +0200 (CEST) In-Reply-To: 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: Raymond Yau Cc: Manuel Jander , alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On 6/29/2012 8:03 PM, Raymond Yau wrote: > Do suspsend/resume affect the usage of the wall clock ? Those au88x0 > also have a 32 bit register which return the ticks from a 12.288 Mz > oscillator (i.e. 256 x 48000Hz) , this register wrap around in around > 349.5 seconds Can this clock be used to determine the drift too ? In theory any clock can be used, as long as it's synchronous with the bitclock used in the serial stream. I am planning to use our 19.2 MHz clock on non HDAudio platforms, a 12.288 would work at well. The cycle count will be translated to ns, the initial clock base has a marginal impact on the result. I haven't validated anything related to suspend/resume. It should work if the trigger is invoked on resume where the audio wallclock is reinitialized with the system time -Pierre