Re: [PATCH v2 10/10] usb: dwc2/gadget: rework suspend/resume code to correctly restore gadget state

[Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>]

Hello,

On 2014-10-27 08:18, Marek Szyprowski wrote:
> On 2014-10-25 03:16, Paul Zimmerman wrote:
> > > From: Marek Szyprowski [mailto:m.szyprowski@xxxxxxxxxxx]
> > > Sent: Monday, October 20, 2014 3:46 AM
> > >
> > > Suspend/resume code assumed that the gadget was always enabled and
> > > connected to usb bus. This means that the actual state of the gadget
> > > (soft-enabled/disabled or connected/disconnected) was not correctly
> > > preserved on suspend/resume cycle. This patch fixes this issue.
> > >
> > > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > > ---
> > >   drivers/usb/dwc2/core.h   |  4 +++-
> > >   drivers/usb/dwc2/gadget.c | 43 
> > > +++++++++++++++++++++++++++----------------
> > >   2 files changed, 30 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
> > > index bf015ab3b44c..3648b76a18b4 100644
> > > --- a/drivers/usb/dwc2/core.h
> > > +++ b/drivers/usb/dwc2/core.h
> > > @@ -210,7 +210,9 @@ struct s3c_hsotg {
> > >       u8                      ctrl_buff[8];
> > >
> > >       struct usb_gadget       gadget;
> > > -    unsigned int            setup;
> > > +    unsigned int            setup:1;
> > > +    unsigned int        connected:1;
> > > +    unsigned int        enabled:1;
> > >       unsigned long           last_rst;
> > >       struct s3c_hsotg_ep     *eps;
> > >   };
> > > diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> > > index 0d34cfc71bfb..c6c6cf982c90 100644
> > > --- a/drivers/usb/dwc2/gadget.c
> > > +++ b/drivers/usb/dwc2/gadget.c
> > > @@ -2925,6 +2925,8 @@ static int s3c_hsotg_udc_start(struct 
> > > usb_gadget *gadget,
> > >       spin_lock_irqsave(&hsotg->lock, flags);
> > >       s3c_hsotg_init(hsotg);
> > >       s3c_hsotg_core_init_disconnected(hsotg);
> > > +    hsotg->enabled = 1;
> > > +    hsotg->connected = 0;
> > >       spin_unlock_irqrestore(&hsotg->lock, flags);
> > >
> > >       dev_info(hsotg->dev, "bound driver %s\n", driver->driver.name);
> > > @@ -2961,6 +2963,8 @@ static int s3c_hsotg_udc_stop(struct 
> > > usb_gadget *gadget,
> > >
> > >       hsotg->driver = NULL;
> > >       hsotg->gadget.speed = USB_SPEED_UNKNOWN;
> > > +    hsotg->enabled = 0;
> > > +    hsotg->connected = 0;
> > >
> > >       spin_unlock_irqrestore(&hsotg->lock, flags);
> > >
> > > @@ -2999,11 +3003,14 @@ static int s3c_hsotg_pullup(struct 
> > > usb_gadget *gadget, int is_on)
> > >       dev_dbg(hsotg->dev, "%s: is_on: %d\n", __func__, is_on);
> > >
> > >       spin_lock_irqsave(&hsotg->lock, flags);
> > > +
> > >       if (is_on) {
> > >           clk_enable(hsotg->clk);
> > > +        hsotg->connected = 1;
> > >           s3c_hsotg_core_connect(hsotg);
> > >       } else {
> > >           s3c_hsotg_core_disconnect(hsotg);
> > > +        hsotg->connected = 0;
> > >           clk_disable(hsotg->clk);
> > >       }
> > >
> > > @@ -3652,16 +3659,18 @@ static int s3c_hsotg_suspend(struct 
> > > platform_device *pdev, pm_message_t state)
> > >           dev_info(hsotg->dev, "suspending usb gadget %s\n",
> > >                hsotg->driver->driver.name);
> > >
> > > -    spin_lock_irqsave(&hsotg->lock, flags);
> > > -    s3c_hsotg_core_disconnect(hsotg);
> > > -    s3c_hsotg_disconnect(hsotg);
> > > -    hsotg->gadget.speed = USB_SPEED_UNKNOWN;
> > > -    spin_unlock_irqrestore(&hsotg->lock, flags);
> > > +    if (hsotg->enabled) {
> > Hmm. Are you sure it's safe to check ->enabled outside of the spinlock?
> > What happens if s3c_hsotg_udc_stop() runs right after this, before the
> > spinlock is taken, and disables stuff? Sure, it's a tiny window, but
> > still...
>
> This code is called only in system suspend path, when userspace has 
> been already frozen.
> udc_stop() can be called only as a result of userspace action, so it 
> is imho safe to
> assume that the above code doesn't need additional locking.

However if you prefer the version with explicit locking, I will send v3 
in a few minutes.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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