linux-kernel - Re: [PATCH v3] USB: Don't set USB_PORT_FEAT

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Message-ID: <20210419141921.GA133494@rowland.harvard.edu>
Date:   Mon, 19 Apr 2021 10:19:21 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Chris Chiu <chris.chiu@...onical.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, m.v.b@...box.com,
        hadess@...ess.net, linux-usb@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] USB: Don't set USB_PORT_FEAT_SUSPEND on WD19's
 Realtek Hub

On Mon, Apr 19, 2021 at 01:11:38AM -0400, Chris Chiu wrote:
> Sorry that I didn't make myself clear. I found that if I applied RESET_RESUME
> quirk on the problematic hub, the Set-Port-Feature(suspend) timeout error
> disappeared. SInce the timeout is not happening for each suspend by default,
> I suspect maybe reset-resume take everything back to clean state for the hub
> and the Set-Port-Feature(suspend) can be taken care of w/o problems.

Okay, that's a good solution for system	suspend.

> I didn't like RESET_RESUME because runtime PM would not work on the quirked
> device.

A more interesting question is whether it will work for	devices	plugged	
into the hub.  Even though the hub won't be runtime suspended, the 
things attached	to it might be.

>  But if the Set-Port-Feature(suspend) can't be handled and
> skipped, I can't
> expect the runtime PM to work for all devices connected to the hub either.
> Is that right? If what I proposed in the patch can not get better
> result than existing
> quirk, I think using the RESET_RESUME would be a better option. Any suggestions?

Try the RESET_RESUME quirk and see how well it works with runtime 
suspend.

Alan Stern