From: Philipp Zabel <p.zabel@pengutronix.de>
To: Mark Brown <broonie@kernel.org>, Marco Felsch <m.felsch@pengutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>,
Rob Herring <robh@kernel.org>,
Linux-ALSA <alsa-devel@alsa-project.org>,
Lars-Peter Clausen <lars@metafoo.de>,
devicetree@vger.kernel.org, Sascha Hauer <s.hauer@pengutronix.de>,
Liam Girdwood <lgirdwood@gmail.com>,
kernel@pengutronix.de
Subject: Re: [PATCH] ASoC: ssm2602: Fix ADC powerup sequencing
Date: Fri, 25 May 2018 17:18:09 +0200 [thread overview]
Message-ID: <1527261489.4938.9.camel@pengutronix.de> (raw)
In-Reply-To: <20180525145245.GM4828@sirena.org.uk>
On Fri, 2018-05-25 at 15:52 +0100, Mark Brown wrote:
> On Fri, May 25, 2018 at 01:42:53PM +0200, Marco Felsch wrote:
>
> > Also the formula for the delay time (t = C × 25,000/3.5) depends only on
> > the capacity size.
>
> Why not just have the user specify the capacitance of the capacitor on
> the rail which they can directly read from the schematic rather than
> forcing them to do the calcualtion? That seems a bit clearer and more
> user friendly (plus if someone decides the spec was wrong it's easier to
> roll out fixes).
The exact capacitance may not be known or vary above the nominal value
because of cheap components, and the formula from the datasheet is just
a guideline.
I'd expect the usual method to set this delay to be semi-empirical:
"start from the value calculated from datasheet and schematics and then
increase until no more audio artifacts on a representative sample of
boards".
I think it is be better to specify a delay that works than a bogus
capacitance value that happens to correspond to a delay that works.
regards
Philipp
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next prev parent reply other threads:[~2018-05-25 15:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-17 13:30 [PATCH] ASoC: ssm2602: Fix ADC powerup sequencing Marco Felsch
2018-05-17 16:14 ` Rob Herring
2018-05-18 10:46 ` Philipp Zabel
2018-05-23 16:53 ` Rob Herring
2018-05-25 9:47 ` Marco Felsch
2018-05-25 10:26 ` Mark Brown
2018-05-25 11:42 ` Marco Felsch
2018-05-25 14:52 ` Mark Brown
2018-05-25 15:18 ` Philipp Zabel [this message]
2018-05-25 17:24 ` Mark Brown
2018-06-05 9:58 ` Philipp Zabel
2018-06-05 16:06 ` Mark Brown
2018-05-25 15:42 ` Rob Herring
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