linux-kernel - Re: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB suspend

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Message-ID: <Pine.LNX.4.44L0.1606081352250.2191-100000@iolanthe.rowland.org>
Date:	Wed, 8 Jun 2016 15:13:56 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Wenyou Yang <wenyou.yang@...el.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Brown <broonie@...nel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] usb: ohci-at91: Forcibly suspend ports while USB
 suspend

On Wed, 8 Jun 2016, Wenyou Yang wrote:

> In order to the save power consumption, as a workaround, suspend
> forcibly the USB PORTA/B/C via set the SUSPEND_A/B/C bits of OHCI
> Interrupt Configuration Register in the SFRs while OHCI USB suspend.
> 
> This suspend operation must be done before the USB clock is disabled,
> resume after the USB clock is enabled.
> 
> Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> ---

You never answered the questions I posted for the first version of this 
patch:

What does this mean?  What does suspending a port do?  Is it the same 
as a normal USB port suspend?

If it is the same, why doesn't the USB_PORT_FEAT_SUSPEND subcase of the 
SetPortFeature case in ohci_hub_control() already take care of this?

Alan Stern