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Re: [PATCH] usb-musb: keep VBUS on when device is disconnected

From Moreno Bartalucci <moreno.bartalucci@tecnorama.it>
Newsgroups linux.kernel
Subject Re: [PATCH] usb-musb: keep VBUS on when device is disconnected
Date 2017-03-27 15:00 +0200
Message-ID <tpCpA-8bK-15@gated-at.bofh.it> (permalink)
References <tlipr-wL-1@gated-at.bofh.it> <toCBj-5D8-5@gated-at.bofh.it> <toOj7-5Ya-5@gated-at.bofh.it>
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> Il giorno 25 mar 2017, alle ore 08:21, Lars Melin <larsm17@gmail.com> ha scritto:
> 
>> 
>> The usb device has been disconnected, why it still cares about VBUS
>> power?
> 
> Morphing devices (3G dongles, wifi dongles, some printers) boots up in install mode, usually only as a virtual cd-rom containing Windows drivers and software.
> [...]
> why a host only configured port should cut the VBUS supply, it could be always on right?
> 

Yes, that’s exactly the problem I tried to solve with this patch.
I have to add that the problem was not there with kernels up to 4.8.17, I started to see it with 4.9 and up.

By git-bisecting kernel sources, it appears this behaviour has been introduced by this commit:

2f3fd2c5bde1f94513c3dc311ae64494085ec371

I also agree that, in my opinion, a host only port should never remove the VBUS supply, as it happens on all the PCs (linux+windows+mac) that I tested until now.

I saw this problem on a beaglebone black. Of course I’m available to do all the tests that you might suggest me to help you better understand the issue.

Moreno Bartalucci

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Thread

[PATCH] usb-musb: keep VBUS on when device is disconnected Moreno Bartalucci <moreno.bartalucci@tecnorama.it> - 2017-03-15 15:50 +0100
  Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Bin Liu <b-liu@ti.com> - 2017-03-24 20:00 +0100
    Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Lars Melin <larsm17@gmail.com> - 2017-03-25 08:30 +0100
      Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Moreno Bartalucci <moreno.bartalucci@tecnorama.it> - 2017-03-27 15:00 +0200
        Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Bin Liu <b-liu@ti.com> - 2017-03-27 15:20 +0200
          Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Tony Lindgren <tony@atomide.com> - 2017-03-27 16:50 +0200
            Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Moreno Bartalucci <moreno.bartalucci@tecnorama.it> - 2017-03-27 18:30 +0200
              Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Tony Lindgren <tony@atomide.com> - 2017-03-27 19:20 +0200
                Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Bin Liu <b-liu@ti.com> - 2017-03-27 19:20 +0200
                Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Tony Lindgren <tony@atomide.com> - 2017-03-27 20:00 +0200
                Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Moreno Bartalucci <moreno.bartalucci@tecnorama.it> - 2017-03-28 08:20 +0200
                Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Tony Lindgren <tony@atomide.com> - 2017-03-28 17:10 +0200

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