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Date:      Thu, 11 Feb 2016 12:48:42 +0100
From:      Hans Petter Selasky <hps@selasky.org>
To:        Dee Zay <julianpark90611@gmail.com>
Cc:        freebsd-acpi@freebsd.org
Subject:   Re: Regarding Wake On USB input from S3 Sleep
Message-ID:  <56BC751A.4030707@selasky.org>
In-Reply-To: <CACMcRdfk6_jba3YJhi=uPwo82CG1NmfAkM06sOs_EcKGmf_VFg@mail.gmail.com>
References:  <CACMcRdfLERKud5_0GMKK1m7RF1DS8hxrhSxpZFEUyqpMWNS7EQ@mail.gmail.com> <56BC289F.2070208@selasky.org> <CACMcRdcVnCshhPpc9qAyGeg62DgYxFxRbkiNMVsCeMF7SOmmrA@mail.gmail.com> <56BC31CD.2000509@selasky.org> <CACMcRdfk6_jba3YJhi=uPwo82CG1NmfAkM06sOs_EcKGmf_VFg@mail.gmail.com>

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On 02/11/16 12:30, Dee Zay wrote:
> Hello,
>
> I am a bit confused about the resume problem and its procedures.
> Could you explain briefly about the difference between resuming from
> standby(powered) and completely off HC?
>
> Thank you,
> Julian

Hi,

Only the XHCI can resume completely off HC. It knows about which devices 
are enumerated and so on. The other HC's don't.

You need to ensure that filesystem reloads everything when you resume. 
No assumptions can be made about which disk is connected. A USB keyboard 
is simpler, of course.

There is also something called a BIOS, which sometimes enable and 
enumerate the USB devices before the OS is resuming. I think there is a 
standard somewhere how the BIOS can handover enumerated devices to the 
USB stack, but I'm not sure if it is public. In any case FreeBSD will 
reset the HC and start from scratch when resuming. That always works.

--HPS



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