Re: [PATCH 1/2] ASoC: codecs: wsa883x: do not set can_multi_write flag

From: Srinivas Kandagatla
Date: Wed May 24 2023 - 06:10:07 EST

On 24/05/2023 10:48, Mark Brown wrote:
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?

No, Codec does not have any such interface to write to device registers directly without going via Soundwire.

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.

By the looks of the code, its other way around.

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.