Re: [PATCH usb-next v4 0/2] fix HCD PHY suspend handling

[Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>]

On Thu, Apr 05, 2018 at 11:47:11AM +0300, Roger Quadros wrote:
> Greg,
> 
> On 28/03/18 00:26, Martin Blumenstingl wrote:
> > This is a follow-up to my previous series "initialize (multiple) PHYs
> > for a HCD": [0].
> > 
> > Roger Quadros reported [1] that it "is breaking low power cases on TI
> > SoCs when USB is in host mode". He further explains that "Not doing the
> > phy_exit() here [when entering suspend] leaves the clocks enabled on
> > our SoC and we're no longer able to reach low power states on system
> > suspend."
> > Chunfeng Yun from Mediatek noted [2] that we cannot unconditionally call
> > phy_exit while entering system suspend, because this would "disconnect
> > plugged devices on MTK platforms, due to re-initialize u2 phys when
> > resume"
> > 
> > In the discussion (which followed Roger's bug report: [1]) Roger,
> > Chunfeng and me came to the conclusion that we can fix suspend on the
> > TI SoCs without breaking it on the Mediatek SoCs by extending the
> > suspend and resume code in usb/core/phy.c by checking whether the USB
> > controller can wake up the system (which is the case for the Mediatek
> > MTU3 controller, but now for the dwc3 controller used on the TI SoCs):
> > - if the controller can wake up the system (Mediatek MTU3 use-case) we
> >   only call usb_phy_roothub_power_off (which calls phy_power_off) when
> >   entering system suspend
> > - if the controller however cannot wake up the system (dwc3 on TI SoCs)
> >   we additionally call usb_phy_roothub_exit (which calls phy_exit) when
> >   entering system suspend
> > - (we undo the previous steps during system resume)
> > 
> > The goal of this series is to fix the issue reported by Roger without
> > breaking suspend/resume on the Mediatek SoCs.
> > Since I neither have a TI nor a Mediatek device I am sending this as
> > RFC. I have tested it on an Amlogic Meson GXM board (Khadas VIM2) which
> > does NOT support suspend/resume yet.
> > 
> > this should be applied on top of [3] "usb: core: phy: fix return value
> > of usb_phy_roothub_exit()" (even though there's no strict dependency,
> > this is the order I wrote the patches in).
> > 
> > changes since RFC v3 at [6]:
> > - added Chunfeng Yun's Tested-by and Roger Quadros' Reviewed-by (thank
> >   you!)
> > - dropped RFC prefix
> > 
> > changes since RFC v2 at [5]:
> > - add missing INIT_LIST_HEAD call in usb_phy_roothub_add_phy (affects
> >   patch #1 - spotted by Roger Quadros, thank you!)
> > - fixed swapped conditions using device_may_wakeup() in
> >   usb_phy_roothub_resume because we need to call usb_phy_roothub_init
> >   if the controller cannot wake up the device (affects patch #2, spotted
> >   by Chunfeng Yun, thank you!)
> > - simplified the error condition to "undo" usb_phy_roothub_init if
> >   usb_phy_roothub_power_on failed in usb_phy_roothub_resume (suggested
> >   by Chunfeng Yun)
> > - updated the commit message (using Roger's wording) because (quote from
> >   Roger "it doesn't prevent the system from entering suspend but just
> >   prevents the system from reaching lowest power levels in the suspend
> >   state."
> > 
> > Changes since RFC v1 (blob attachments) at [4]:
> > - use device_may_wakeup instead of device_can_wakeup as suggested by
> >   Roger Quadros
> > - use the controller device from hcd->self.controller as suggested by
> >   Chunfeng Yun
> > - compile time fixes thanks to Roger Quadros
> > - if usb_phy_roothub_power_on in usb_phy_roothub_resume failes then
> >   we now call usb_phy_roothub_exit to keep the PHYs in the correct
> >   state if usb_phy_roothub_resume partially failed
> > 
> > 
> > [0] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006599.html
> > [1] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006737.html
> > [2] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006758.html
> > [3] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006819.html
> > [4] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006794.html
> > [5] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006820.html
> > [6] http://lists.infradead.org/pipermail/linux-amlogic/2018-March/006847.html
> > 
> > Martin Blumenstingl (2):
> >   usb: core: split usb_phy_roothub_{init,alloc}
> >   usb: core: use phy_exit during suspend if wake up is not supported
> 
> Gentle ping on this one. Without this system suspend/resume is broken on TI platforms.

Sorry, this missed my merge window, I can pick it up after 4.17-rc1 is
out.

thanks,

greg k-h