linux-kernel - Re: [PATCH v3 17/20] ASoC: dt-bindings: tas2770: add flags for SDOUT pulldown and zero-fill

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Message-ID: <CAHgNfTyVKFuT0fZ3Qj=MdcXs67KscwkSepAH95xkAAKWM1g8Xg@mail.gmail.com>
Date: Wed, 5 Mar 2025 01:19:15 +0000
From: James Calligeros <jcalligeros99@...il.com>
To: Rob Herring <robh@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, Shenghao Ding <shenghao-ding@...com>, 
	Kevin Lu <kevin-lu@...com>, Baojun Xu <baojun.xu@...com>, Dan Murphy <dmurphy@...com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Shi Fu <shifu0704@...ndersoft.com>, Jean Delvare <jdelvare@...e.com>, 
	Guenter Roeck <linux@...ck-us.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>, 
	Martin Povišer <povik+lin@...ebit.org>, 
	Hector Martin <marcan@...can.st>, linux-sound@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	asahi@...ts.linux.dev, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v3 17/20] ASoC: dt-bindings: tas2770: add flags for SDOUT
 pulldown and zero-fill

On Tue, Mar 4, 2025 at 1:50 PM Rob Herring <robh@...nel.org> wrote:
> Can't you align this with the other property you added? Or extend the
> existing TDM properties we have.

I don't think either option makes sense given the functionality. This chip
behaves differently to TAS2764, and instead of using a bitmask to determine
which slots to ignore, we only get a single bit to tell the chip whether we want
it to fill or pull down *all* inactive slots. The property being a u32 mask
therefore does not make sense here.

Building the logic off the existing generic TDM slot properties would alter
behaviour of existing implementations where zero-fill and pulldown may not be
required or even wanted. This may continue to be the case going forward so I'd
rather make it an explicit opt-in rather than some unconditional thing we try to
turn on heuristically.

I gave some thought to flipping these bits if a TDM slot mask is passed to the
driver, however it can still be the case that we don't want both zero-fill *and*
pulldown active at the same time, or as above some implementations may want
neither, so we still need to be able to specify them individually.

Regards,
James