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

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Message-ID: <aeeb0dfb-87e2-4024-9d4a-0b9529477315@linaro.org>
Date: Mon, 15 Jan 2024 21:43:21 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Javier Carrasco <javier.carrasco@...fvision.net>,
 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,
 linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/3] ASoC: dt-bindings: xmos,xvf3500: add bindings for
 XMOS XVF3500

On 15/01/2024 20:43, Javier Carrasco wrote:
> On 15.01.24 19:11, Krzysztof Kozlowski wrote:
>> On 15/01/2024 17:24, Javier Carrasco wrote:
>>> 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.
>>
>> I believe it should be just like onboard hub. I don't understand why
>> onboard hub was limited to hub, because other USB devices also could be
>> designed similarly by hardware folks :/
>>
>> And if we talk about Linux drivers, then your current solution does not
>> support suspend/resume and device unbind.
>>
>> Best regards,
>> Krzysztof
>>
> 
> Actually this series is an attempt to get rid of a misuse of the
> onboard_usb_hub driver by a device that is not a HUB, but requires the
> platform-part of that driver for the initialization.

That's just naming issue, isn't it?

> 
> What would be the best approach to provide support upstream? Should I
> turn this driver into a generic USB driver that does what the
> platform-part of the onboard HUB does? Or are we willing to accept

No, because you did not solve the problems I mentioned. This is neither
accurate hardware description nor proper Linux driver model handling PM
and unbind.

> non-HUB devices in the onboard_usb_hub driver even though it supports
> more operations?
> 
> I am adding linux-usb to this thread in case someone has other suggestions.

I don't see any difference between this device and onboard hub. The
concept and the problem is the same. Therefore either treat it as as
onboard hub or come with USB-version of PCI power sequencing.

https://lore.kernel.org/all/20240104130123.37115-1-brgl@bgdev.pl/

Best regards,
Krzysztof