linux-kernel - Re: [PATCH 1/2] ASoC: codecs: wsa883x: do not set can_multi

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Date:   Wed, 24 May 2023 10:48:40 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     perex@...ex.cz, tiwai@...e.com, lgirdwood@...il.com,
        ckeepax@...nsource.cirrus.com, kuninori.morimoto.gx@...esas.com,
        linux-kernel@...r.kernel.org, pierre-louis.bossart@...ux.intel.com,
        alsa-devel@...a-project.org
Subject: Re: [PATCH 1/2] ASoC: codecs: wsa883x: do not set can_multi_write
 flag

On Wed, May 24, 2023 at 10:42:21AM +0100, Srinivas Kandagatla wrote:
> On 24/05/2023 09:57, Mark Brown wrote:

> > I'm unclear, is this a limitation of the hardware or of the current
> > Soundwire code?

> Its both.

> Codec itself does not have any private write callback to support this and
> AFAIU Qualcomm Soundwire controller does not have any such hw facility to
> program multi-registers for device at one shot.

How about the *CODEC* hardware?

> Is write callback used for both Bulk writes and multi-writes?

Only multi-write at this point but we probably should consider redoing
bulk writes to use it as well.

> Is multi-write feature of regmap bus or device?

Well, I don't think any buses that understand registers have implemented
it yet but there's nothing fundamental that means that a bus couldn't
usefully do something with multi-write.  The current users all use raw
buses that don't know anything about registers or values.

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