linux-kernel - RE: [PATCH] ASoC: da7219: remove SRM lock check retry

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Message-ID: <CF33C36214C39B4496568E5578BE70C7403CACC7@PGSMSX108.gar.corp.intel.com>
Date:   Tue, 3 Dec 2019 14:36:23 +0000
From:   "Lu, Brent" <brent.lu@...el.com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
CC:     Support Opensource <Support.Opensource@...semi.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ASoC: da7219: remove SRM lock check retry

> 
> But on platforms where they can enable the WCLK early they shouldn't be
> looping around here for anything like 400ms. In an ideal world when that
> widget is run SRM should hopefully be already locked but the code does
> allow for some delay. Actually, having a long delay also helps show the user
> that something isn't right here so I'm somewhat loathed to change this.
> 
> Even if you do reduce the retry timings what you're still not protecting
> against is the possibility of audio artefacts when SRM finally locks. You want
> this to lock before the any of the audio path is up so I think we need to find a
> way to resolve that rather than relying on getting lucky with a smooth power-
> up.
> 
Hi Adam,

Thanks for the explanation. So the purpose of the code is providing some
timing tolerance for SRM to lock? If so, I would suggest adding warning message
for the lock fail so people have a clue if their design fails the CTS test. Hard to say
if Google further reduces the Cold latency again in the future.


Regards,
Brent