linux-kernel - Re: [PATCH v3 2/2] ASoC: tas5805m: add missing page switch.

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Message-ID: <20230206204546.GA233871@nyquist.nev>
Date:   Tue, 7 Feb 2023 09:45:46 +1300
From:   Daniel Beer <daniel.beer@...rinstitute.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Andy Liu <andy-liu@...com>
Subject: Re: [PATCH v3 2/2] ASoC: tas5805m: add missing page switch.

On Mon, Feb 06, 2023 at 01:11:09PM +0000, Mark Brown wrote:
> On Thu, Oct 27, 2022 at 09:38:38PM +1300, Daniel Beer wrote:
> > In tas5805m_refresh, we switch pages to update the DSP volume control,
> > but we need to switch back to page 0 before trying to alter the
> > soft-mute control. This latter page-switch was missing.
> 
> You should just use the register windowing support in regmap, it will
> take care of this for you, avoiding any further similar errors.

Hi Mark,

Thanks for reviewing.

We did discuss this a while back when the driver first went in.
Unfortunately the vendor software tools provide configuration for the
part in the form of a sequence of raw register writes, including
explicit page changes:

    https://lore.kernel.org/lkml/Yd85bjKEX9JnoOlI@sirena.org.uk/

Aside from this, I have two other practical issues.

The first is that I'm not sure how exactly to implement the paging
scheme in terms of regmap_range_cfg (assuming this is what you're
referring to). This chip has multi-level paging (books/pages), with the
book selection register itself requiring paging to access. A sequence of
three register writes is therefore required in the general case to
select the correct page. I had a quick look at a random assortment of
existing regmap_range_cfg uses, but didn't find anything that looked
like the same problem.

Secondly, the patches as submitted here have been tested, but I don't
currently have access to hardware. I'm very hesitant to make a
significant change without retesting and leave the driver in a broken
state again.

Cheers,
Daniel

-- 
Daniel Beer
Firmware Engineer at Igor Institute
daniel.beer@...rinstitute.com or +64-27-420-8101
Offices in Seattle, San Francisco, and Vancouver BC or (206) 494-3312