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

[Yang, Wenyou]

Hi Alan, 

> -----Original Message-----
> From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx]
> Sent: 2016年6月9日 3:14
> To: Yang, Wenyou <Wenyou.Yang@xxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Ferre, Nicolas
> <Nicolas.FERRE@xxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Pawel Moll
> <pawel.moll@xxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>; Ian Campbell
> <ijc+devicetree@xxxxxxxxxxxxxx>; Kumar Gala <galak@xxxxxxxxxxxxxx>;
> Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>; Kernel development
> list <linux-kernel@xxxxxxxxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; USB list <linux-usb@xxxxxxxxxxxxxxx>
> 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@xxxxxxxxx>
> > ---
> 
> 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?

I remembered I answered your questions, http://lists.infradead.org/pipermail/linux-arm-kernel/2016-May/429245.html

Maybe not very clear.

> 
> Alan Stern


Best Regards,
Wenyou Yang