On Tue, Dec 06, 2016 at 06:29:31PM +0530, Sekhar Nori wrote: > On Monday 05 December 2016 10:17 PM, Bin Liu wrote: > > On Fri, Dec 02, 2016 at 03:23:50PM +0100, Alexandre Bailon wrote: > >> On 11/29/2016 06:56 PM, Bin Liu wrote: > >>> On Tue, Nov 29, 2016 at 06:41:04PM +0100, Alexandre Bailon wrote: > >>>> On 11/29/2016 05:16 PM, Bin Liu wrote: > >>>>> Hi, > >>>>> > >>>>> On Mon, Nov 28, 2016 at 05:26:20PM +0100, Alexandre Bailon wrote: > >>>>>> On da8xx, VBUS is not maintained during suspend when musb is in host mode. > >>>>>> On resume, all the connected devices will be disconnected and then will > >>>>>> be enumerated again. > >>>>>> This happens because MUSB_DEVCTL is cleared during suspend. > >>>>>> Add a quirk to preserve MUSB_DEVCTL during a suspend. > >>>>> > >>>>> Will preserving MUSB_DEVCTL prevent the device getting disconnected? > >>>> Yes. Preserving MUSB_DEVCTL keeps VBUS on though the PHY is off during > >>>> suspend. > >>> > >>> VBUS will be on, but does it prevent disconnecting the usb device on > >>> resume? I don't have a DA8xx to test, but I doubt it, since the PHY is > >>> off. > >> Actually, the PHY is not really off. > > > > I guess the PHY should be off when the system is suspended for an > > aggressive power saving. > > > > Sekhar, any comments? > > No, nothing from my side. I haven't really played with this side of > DA850 at all. Ok, I wanted to know the power requirement in system suspend - do we want to power off the PHY to save power as much as possible, or leave the PHY on to not disconnect enumerated devices. > > For your reference, this is what chapter 10.11.1 referenced by Alexandre > says: > > " > The USB modules can be clock gated using the PSC; however, this does not > power down/clock gate the PHY logic. You can put the USB2.0 PHY and OTG > module in the lowest power state, when not in use, by writing to the > USB0PHYPWDN and the USB0OTGPWRDN bits in the Chip Configuration 2 > Register (CFGCHIP2) in the System Configuration (SYSCFG) Module chapter. > " It sounds like the PHY cannot be turned off on DA8xx? > > It is little bit ambiguous on if USB0PHYPWDN and USB0OTGPWRDN do really > power down the PHY. > > I would just program the bits suggested by the manual and assume that > the hardware reaches the safest low power state it can reach. > > Thanks, > Sekhar Regards, -Bin. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
