linux-kernel - Re: [PATCH v2 3/8] ASoC: mediatek: mt8188: Treat DMIC_GAINx

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Message-ID: <173e41bd-4fa0-4b54-8739-546536ad7c3b@collabora.com>
Date: Tue, 25 Feb 2025 15:41:53 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
 Matthias Brugger <matthias.bgg@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Trevor Wu <trevor.wu@...iatek.com>
Cc: kernel@...labora.com, linux-sound@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 3/8] ASoC: mediatek: mt8188: Treat DMIC_GAINx_CUR as
 non-volatile

Il 25/02/25 15:33, Nícolas F. R. A. Prado ha scritto:
> The DMIC_GAINx_CUR registers contain the current (as in present) gain of
> each DMIC. During capture, this gain will ramp up until a target value
> is reached, and therefore the register is volatile since it is updated
> automatically by hardware.
> 
> However, after capture the register's value returns to the value that
> was written to it. So reading these registers returns the current gain,
> and writing configures the initial gain for every capture.
> 
>  From an audio configuration perspective, reading the instantaneous gain
> is not really useful. Instead, reading back the initial gain that was
> configured is the desired behavior. For that reason, consider the
> DMIC_GAINx_CUR registers as non-volatile, so the regmap's cache can be
> used to retrieve the values, rather than requiring pm runtime resuming
> the device.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>