linux-kernel - RE: [alsa-devel] [PATCH] ASoC: da7219: check SRM lock in trigger callback

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Message-ID: <SN6PR11MB2670FA720AB341183478A00B97100@SN6PR11MB2670.namprd11.prod.outlook.com>
Date:   Wed, 19 Feb 2020 05:57:11 +0000
From:   "Lu, Brent" <brent.lu@...el.com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "Sridharan, Ranjani" <ranjani.sridharan@...el.com>
CC:     "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "Support Opensource" <Support.Opensource@...semi.com>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Chiang, Mac" <mac.chiang@...el.com>,
        "Mark Brown" <broonie@...nel.org>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        "cychiang@...gle.com" <cychiang@...gle.com>
Subject: RE: [alsa-devel] [PATCH] ASoC: da7219: check SRM lock in trigger
 callback

> 
> Am not going to make myself popular here. It's MCLK and FSYNC (or WCLK as
> it's termed for our device) that is required for SRM to lock in the PLL.
> 
> So far I've not found a way in the codec driver to be able to get around this.
> I spent a very long time with Sathya in the early days (Apollo Lake) looking at
> options but nothing would fit which is why I have the solution that's in place
> right now. We could probably reduce the number of rechecks before
> timeout in the driver but that's really just papering over the crack and there's
> still the possibility of noise later when SRM finally does lock.

Hi Adam,

For Google CTS requirement (200ms cold output latency), we plan to upload a
patch which reduces the recheck number to 4 and interval to 20ms so the total
delay here would be 80ms for our platform. We think the time is still sufficient
for other platforms to generate a stable WCLK and for the codec SRM to lock but
still needs your confirmation. How do you think?


Regards,
Brent