RE: [PATCH/RFC v3 3/4] usb: gadget: udc: renesas_usb3: use usb role switch API

[Yoshihiro Shimoda]

Hi Simon-san,

> From: Simon Horman, Sent: Tuesday, May 15, 2018 5:04 PM
> 
> On Tue, May 15, 2018 at 08:02:00AM +, Yoshihiro Shimoda wrote:
> > Hi Simon-san,
> >
> > Thank you for your review!
> >
> > > From: Simon Horman, Sent: Tuesday, May 15, 2018 4:54 PM
> > > On Mon, May 14, 2018 at 06:15:59PM +0900, Yoshihiro Shimoda wrote:
> > 
> > > >  static void usb3_set_mode(struct renesas_usb3 *usb3, bool host)
> > > >  {
> > > > -   _usb3_set_mode(usb3, host);
> > > > +   if (usb3->role_sw)
> > > > +   usb_role_switch_set_role(usb3->role_sw, host ?
> > > > +USB_ROLE_HOST : 
> > > > USB_ROLE_DEVICE);
> > > > +   else
> > > > +   _usb3_set_mode(usb3, host);
> > > >  }
> > > >
> > > >  static void usb3_vbus_out(struct renesas_usb3 *usb3, bool enable)
> > > > @@ -672,8 +676,8 @@ static void usb3_mode_config(struct renesas_usb3 
> > > > *usb3, bool host, bool a_dev)
> > > >  {
> > > > unsigned long flags;
> > > >
> > > > -   spin_lock_irqsave(>lock, flags);
> > > > usb3_set_mode(usb3, host);
> > > > +   spin_lock_irqsave(>lock, flags);
> > >
> > > Hi Shimoda-san,
> > >
> > > could you clarify why moving this lock is safe?
> >
> > The usb3_set_mode() is possible to call usb_role_switch_set_role() API
> > and usb_role_switch_set_role() calls mutex_lock().
> > So, this moving this lock (especially avoiding irqsave) needs.
> 
> Thanks, that make sense.
> 
> But usb3_set_mode() may also call _usb3_set_mode().
> It is safe to call _usb3_set_mode() without holding the lock?

Thank you for the pointed out. I am thinking it is possible to be
unsafe without holding the lock. So, I'd like to improve this patch somehow
(for example: Add new usb role switch APIs without mutex).

Best regards,
Yoshihiro Shimoda

Re: [PATCH/RFC v3 3/4] usb: gadget: udc: renesas_usb3: use usb role switch API

[Simon Horman]

On Tue, May 15, 2018 at 08:02:00AM +, Yoshihiro Shimoda wrote:
> Hi Simon-san,
> 
> Thank you for your review!
> 
> > From: Simon Horman, Sent: Tuesday, May 15, 2018 4:54 PM
> > On Mon, May 14, 2018 at 06:15:59PM +0900, Yoshihiro Shimoda wrote:
> 
> > >  static void usb3_set_mode(struct renesas_usb3 *usb3, bool host)
> > >  {
> > > - _usb3_set_mode(usb3, host);
> > > + if (usb3->role_sw)
> > > + usb_role_switch_set_role(usb3->role_sw, host ?
> > > +  USB_ROLE_HOST : USB_ROLE_DEVICE);
> > > + else
> > > + _usb3_set_mode(usb3, host);
> > >  }
> > >
> > >  static void usb3_vbus_out(struct renesas_usb3 *usb3, bool enable)
> > > @@ -672,8 +676,8 @@ static void usb3_mode_config(struct renesas_usb3 
> > > *usb3, bool host, bool a_dev)
> > >  {
> > >   unsigned long flags;
> > >
> > > - spin_lock_irqsave(>lock, flags);
> > >   usb3_set_mode(usb3, host);
> > > + spin_lock_irqsave(>lock, flags);
> > 
> > Hi Shimoda-san,
> > 
> > could you clarify why moving this lock is safe?
> 
> The usb3_set_mode() is possible to call usb_role_switch_set_role() API
> and usb_role_switch_set_role() calls mutex_lock().
> So, this moving this lock (especially avoiding irqsave) needs.

Thanks, that make sense.

But usb3_set_mode() may also call _usb3_set_mode().
It is safe to call _usb3_set_mode() without holding the lock?

> Best regards,
> Yoshihiro Shimoda
> 
> > >   usb3_vbus_out(usb3, a_dev);
> > >   /* for A-Peripheral or forced B-device mode */
> > >   if ((!host && a_dev) ||
> > > --
> > > 1.9.1
> > >
> 

RE: [PATCH/RFC v3 3/4] usb: gadget: udc: renesas_usb3: use usb role switch API

[Yoshihiro Shimoda]

Hi Simon-san,

Thank you for your review!

> From: Simon Horman, Sent: Tuesday, May 15, 2018 4:54 PM
> On Mon, May 14, 2018 at 06:15:59PM +0900, Yoshihiro Shimoda wrote:

> >  static void usb3_set_mode(struct renesas_usb3 *usb3, bool host)
> >  {
> > -   _usb3_set_mode(usb3, host);
> > +   if (usb3->role_sw)
> > +   usb_role_switch_set_role(usb3->role_sw, host ?
> > +USB_ROLE_HOST : USB_ROLE_DEVICE);
> > +   else
> > +   _usb3_set_mode(usb3, host);
> >  }
> >
> >  static void usb3_vbus_out(struct renesas_usb3 *usb3, bool enable)
> > @@ -672,8 +676,8 @@ static void usb3_mode_config(struct renesas_usb3 *usb3, 
> > bool host, bool a_dev)
> >  {
> > unsigned long flags;
> >
> > -   spin_lock_irqsave(>lock, flags);
> > usb3_set_mode(usb3, host);
> > +   spin_lock_irqsave(>lock, flags);
> 
> Hi Shimoda-san,
> 
> could you clarify why moving this lock is safe?

The usb3_set_mode() is possible to call usb_role_switch_set_role() API
and usb_role_switch_set_role() calls mutex_lock().
So, this moving this lock (especially avoiding irqsave) needs.

Best regards,
Yoshihiro Shimoda

> > usb3_vbus_out(usb3, a_dev);
> > /* for A-Peripheral or forced B-device mode */
> > if ((!host && a_dev) ||
> > --
> > 1.9.1
> >

Re: [PATCH/RFC v3 3/4] usb: gadget: udc: renesas_usb3: use usb role switch API

[Simon Horman]

On Mon, May 14, 2018 at 06:15:59PM +0900, Yoshihiro Shimoda wrote:
> This patch uses usb role switch API if the register suceeeded.
> 
> Signed-off-by: Yoshihiro Shimoda 
> ---
>  drivers/usb/gadget/udc/renesas_usb3.c | 8 ++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/renesas_usb3.c 
> b/drivers/usb/gadget/udc/renesas_usb3.c
> index c878449..bfb5803 100644
> --- a/drivers/usb/gadget/udc/renesas_usb3.c
> +++ b/drivers/usb/gadget/udc/renesas_usb3.c
> @@ -657,7 +657,11 @@ static void _usb3_set_mode(struct renesas_usb3 *usb3, 
> bool host)
>  
>  static void usb3_set_mode(struct renesas_usb3 *usb3, bool host)
>  {
> - _usb3_set_mode(usb3, host);
> + if (usb3->role_sw)
> + usb_role_switch_set_role(usb3->role_sw, host ?
> +  USB_ROLE_HOST : USB_ROLE_DEVICE);
> + else
> + _usb3_set_mode(usb3, host);
>  }
>  
>  static void usb3_vbus_out(struct renesas_usb3 *usb3, bool enable)
> @@ -672,8 +676,8 @@ static void usb3_mode_config(struct renesas_usb3 *usb3, 
> bool host, bool a_dev)
>  {
>   unsigned long flags;
>  
> - spin_lock_irqsave(>lock, flags);
>   usb3_set_mode(usb3, host);
> + spin_lock_irqsave(>lock, flags);

Hi Shimoda-san,

could you clarify why moving this lock is safe?

>   usb3_vbus_out(usb3, a_dev);
>   /* for A-Peripheral or forced B-device mode */
>   if ((!host && a_dev) ||
> -- 
> 1.9.1
>