From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [PATCH 15/27] ALSA: hda - Use timecounter_initialize interface Date: Tue, 2 Jan 2018 13:53:01 -0600 Message-ID: <9f09abee-68b8-4515-131f-0f3e210503b0@linux.intel.com> References: <1513323522-15021-1-git-send-email-sagar.a.kamble@intel.com> <1513323522-15021-16-git-send-email-sagar.a.kamble@intel.com> <20171215165125.avkz25eek56i5md4@localhost> <20171228164944.crphv46zegvwautk@localhost> <1a9a1507-7ca3-459b-c2ce-02fc2afad2ff@intel.com> <3c5734a2-8f97-4a8b-26d4-42852cc86352@linux.intel.com> <20180102182146.vbfnihz73lhgf6lc@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by alsa0.perex.cz (Postfix) with ESMTP id 9E455267556 for ; Tue, 2 Jan 2018 20:53:03 +0100 (CET) In-Reply-To: <20180102182146.vbfnihz73lhgf6lc@localhost> Content-Language: en-US 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: Richard Cochran Cc: alsa-devel@alsa-project.org, Takashi Iwai , linux-kernel@vger.kernel.org, Vinod Koul , Thomas Gleixner , Sagar Arun Kamble List-Id: alsa-devel@alsa-project.org On 1/2/18 12:21 PM, Richard Cochran wrote: > On Tue, Jan 02, 2018 at 11:15:45AM -0600, Pierre-Louis Bossart wrote: >> I wrote the code for HDaudio and I remember wasting time trying to figure >> out the gory details of the cycle counter stuff when all I wanted was a >> conversion from a 24MHz counter to ns values using a 125/3 operation in the >> right order - as explained in the comments > > Would using clocks_calc_mult_shift() work for you? In theory yes, but I'd need to re-check what the results would be. I remember applying the 1/3 factor separately to avoid wrap-around after 4 hours [1], but I can't remember the details on the analysis. I can't figure out what the 'maxsec' argument should be either. [1] http://elixir.free-electrons.com/linux/latest/source/sound/hda/hdac_stream.c#L486