linux-kernel - Re: [PATCH 2/3] ASoC: dt-bindings: xmos,xvf3500: add bindings for XMOS XVF3500

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Date: Mon, 15 Jan 2024 17:24:27 +0100
From: Javier Carrasco <javier.carrasco@...fvision.net>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>
Cc: Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org
Subject: Re: [PATCH 2/3] ASoC: dt-bindings: xmos,xvf3500: add bindings for
 XMOS XVF3500


On 15.01.24 17:03, Krzysztof Kozlowski wrote:
> On 15/01/2024 16:59, Javier Carrasco wrote:
>>>> The voice data and any other information can be retrieved directly via
>>>> USB from userspace. Once in normal operation, the device acts as a
>>>> regular "onboard" USB device and the driver does not need to do any
>>>> further management.
>>>
>>> So is this an USB device? If yes, then shouldn't be just auto-discovered
>>> and you add here some bindings for other device? This looks like coding
>>> power sequence not in USB node, but in some other, new node.
>>>
>>> Best regards,
>>> Krzysztof
>>>
>> It is an USB device that requires two power supplies and a reset to
>> boot. Afterwards it is auto-discovered and functions normally as a
>> regular USB device. In that sense it works like the onboard USB HUBs:
>>
>> https://github.com/torvalds/linux/blob/master/drivers/usb/misc/onboard_usb_hub.c
>>
>> The onboard USB HUB driver is of course more complex because it has to
>> support other features, but the idea of enabling the power supplies and
>> toggling the reset signal is essentially the same.
>>
> 
> Yeah, about that... so this is not really correct device representation
> for DT. There is no such device as XVF3500 outside of USB bus. There is
> XVF3500 but on USB bus and this should be there. In the past we allowed
> such root-level devices just because we did not have other way to handle
> them. Now we have.
> 
> Best regards,
> Krzysztof
> 

Do you mean that the XVF3500 should not be represented as a platform
device and instead it should turn into an USB device represented as a
node of an USB controller? Something like this (Rockchip SoC):

&usb_host1_xhci {
	...

	xvf3500 {
		...
	};
};

Did I get you right or is that not the correct representation? Thank you
again.

Best regards,
Javier Carrasco