linux-kernel - Re: [PATCH v17 1/7] usb: misc: Add onboard_usb

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Date:   Sat, 1 Jan 2022 15:23:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Felipe Balbi <balbi@...nel.org>, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Peter Chen <peter.chen@...nel.org>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Roger Quadros <rogerq@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Bastien Nocera <hadess@...ess.net>
Subject: Re: [PATCH v17 1/7] usb: misc: Add onboard_usb_hub driver

30.12.2021 23:17, Matthias Kaehlcke пишет:
> On Mon, Dec 20, 2021 at 11:05:28PM +0300, Dmitry Osipenko wrote:
>> 16.11.2021 23:07, Matthias Kaehlcke пишет:
>>> +static const struct usb_device_id onboard_hub_id_table[] = {
>>> +	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x0411) }, /* RTS0411 USB 3.0 */
>>> +	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5411) }, /* RTS5411 USB 2.0 */
>>> +	{},
>>> +};
>>
>> RTS5411 two times in the comments?
> 
> One time, the other is RTS0511
> 
>> Internet suggests that RTS5411 is USB 3.0
> 
> Correct, however the chip internally has two hubs, one for USB2 and one for
> USB3:
> 
>   Bus 002 Device 002: ID 0bda:0411 Realtek Semiconductor Corp. 4-Port USB 3.1 Hub
>   Bus 001 Device 002: ID 0bda:5411 Realtek Semiconductor Corp. 4-Port USB 2.1 Hub

Alright, thanks.

>> Are these hubs expected to be powered-on only when upstream port is
>> enabled? Shouldn't runtime PM be used for that somehow?
> 
> In the general case I would expect that a onboard hub is connected to a port
> that is enabled. For now I think it's fine to power the hub always when the
> system is running (which is also the current situation with using always-on
> regulators). If someone has an actual use case where the upstream port can
> be disabled they can add support for that later.
> 

I see that you're handling the wakeup-capable devices during the
driver's suspend, perhaps it should work okay then.

BTW, shouldn't the "companion-hub" need to be turned into a generic USB
property? The onboard-usb-hub looks like a generic thing, but
"companion-hub" is specific to the RTS5411 binding.