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

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Message-ID: <20170512174621.GJ3489@atomide.com>
Date:   Fri, 12 May 2017 10:46:21 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Bin Liu <b-liu@...com>,
        Moreno Bartalucci <moreno.bartalucci@...norama.it>,
        Lars Melin <larsm17@...il.com>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alessio Igor Bogani <abogani@...nel.org>
Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected

* Bin Liu <b-liu@...com> [170512 10:43]:
> On Fri, May 12, 2017 at 10:21:35AM -0700, Tony Lindgren wrote:
> > * Bin Liu <b-liu@...com> [170512 08:24]:
> > > On Fri, May 12, 2017 at 07:58:49AM -0700, Tony Lindgren wrote:
> > > > OK. No better ideas except I think we should probably have a separate
> > > > timer for keeping VBUS on after state changes eventually.
> > > 
> > > Currently with the patch below, VBUS is constantly on for host-only
> > > mode, and this is what we want. Why we need a separate timer? No one
> > > cuts VBUs now for host-only mode.
> > 
> > Oh I was just thinking what we might want to do in the future if
> > we want to cut off VBUS when no devices are connected. If we have
> 
> Okay, I see. But I don't think we will ever want to turn off VBUS when
> no devices attached for host-only mode. Any other controllers do this?
> 
> Turning off VBUS doesn't save us much, because it comes from an external
> power rail, and no one consumes it when no devices are attached.
> 
> I believe keeping the controller idle as what we have now is sufficient.

OK fine with me.

Regards,

Tony