linux-kernel - Re: [PATCH V2 2/6] usb: core: Add ability to skip phy exit on suspend and init on resume

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Date:   Fri, 9 Nov 2018 07:14:50 -0500
From:   Alan Cooper <alcooperx@...il.com>
To:     chunfeng yun <chunfeng.yun@...iatek.com>
Cc:     ": Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Alban Bedel <albeu@...e.fr>, Alex Elder <elder@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Avi Fishman <avifishman70@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        DTML <devicetree@...r.kernel.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Hans de Goede <hdegoede@...hat.com>,
        James Hogan <jhogan@...nel.org>,
        Jianguo Sun <sunjianguo1@...wei.com>,
        Johan Hovold <johan@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        USB list <linux-usb@...r.kernel.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Rishabh Bhatnagar <rishabhb@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>, Roger Quadros <rogerq@...com>
Subject: Re: [PATCH V2 2/6] usb: core: Add ability to skip phy exit on suspend
 and init on resume

On Fri, Nov 9, 2018 at 3:08 AM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
>
> On Thu, 2018-11-08 at 17:50 -0500, Alan Cooper wrote:
> > On Wed, Nov 7, 2018 at 8:43 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
> > >
> > > hi,
> > > On Tue, 2018-10-30 at 18:30 -0400, Alan Cooper wrote:
> > > > On 10/17/18 9:46 PM, Chunfeng Yun wrote:> hi,
> > > > >
> > > > > On Wed, 2018-10-17 at 18:29 -0400, Al Cooper wrote:
> > > > >> Add the ability to skip calling the PHY's exit routine on suspend
> > > > >> and the PHY's init routine on resume. This is to handle a USB PHY
> > > > >> that should have it's power_off function called on suspend but
> > > > cannot
> > > > >> have it's exit function called because on exit it will disable the
> > > > >> PHY to the point where register accesses to the Host Controllers
> > > > >> using the PHY will be disabled and the host drivers will crash.
> > > > >>
> > > > >> This is enabled with the HCD flag "suspend_without_phy_exit" which
> > > > >> can be set from any HCD driver.
> > > > >>
> > > > >> Signed-off-by: Al Cooper<alcooperx@...il.com>
> > > > >> ---
> > > > >>   drivers/usb/core/hcd.c  |  8 ++++----
> > > > >>   drivers/usb/core/phy.c  | 18 ++++++++++++------
> > > > >>   drivers/usb/core/phy.h  |  9 ++++++---
> > > > >>   include/linux/usb/hcd.h |  3 +++
> > > > >>   4 files changed, 25 insertions(+), 13 deletions(-)
> > > > >>
> > >
> > >
> > > > >>       unsigned        skip_phy_initialization:1;
> > > > >>
> > > > >> +    /* Some phys don't want the phy's exit/init called on
> > > > suspend/resume */
> > > > >> +    unsigned        suspend_without_phy_exit:1;
> > > > > As suggested before, you can skip phy's exit/init during
> > > > suspend/resume
> > > > > by enabling wakeup of hcd, so needn't add a new variable for it.
> > > >
> > > > I still need to be able to enable and disable wakeup for this driver.
> > > Just use device_init_wakeup(dev, true) instead of
> > > device_wakeup_enable(dev) for your controller driver, you can try it.
> > >
> > > Sorry for the late replay
> >
> > What about the case where sysfs is used to disable wakeup?
> Oh, It's a problem in this case.
>
> BTW: Why the host driver will crash when access host controller's
> register after power-off phy? they are usually independent.

Unfortunately, they are not independent in our design. The PHY
supplies the clock needed to read/write the OHCI, EHCI and XHCI
registers.

Al

>
> >
> > Al
> > > >
> > > > >
> > > > >> +
> > > > >>       /* The next flag is a stopgap, to be removed when all the
> > > > HCDs
> > > > >>        * support the new root-hub polling mechanism. */
> > > > >>       unsigned        uses_new_polling:1;
> > > > >
> > >
> > >
>
>