Re: [PATCH v2 0/3] usb: musb: da8xx: Fix few issues

[David Lechner]

On 10/28/2016 04:31 AM, Alexandre Bailon wrote:
> On 10/27/2016 08:44 PM, David Lechner wrote:
> > On 10/27/2016 12:16 PM, David Lechner wrote:
> > > On 10/26/2016 05:58 AM, Alexandre Bailon wrote:
> > > > Currently, the USB OTG of the da8xx doesn't work.
> > > > This series intend to fix them.
> > > >
> > > > Change in v2:
> > > > * Fix the error path da8xx_musb_init()
> > > >
> > > > Alexandre Bailon (3):
> > > >   usb: musb: da8xx: Call earlier clk_prepare_enable()
> > > >   phy: da8xx-usb: Configure CFGCHIP2 to support OTG workaround
> > > >   usb: musb: da8xx: Only execute the OTG workaround when phy in OTG mode
> > > >
> > > >  drivers/phy/phy-da8xx-usb.c | 17 ++++++++++++-----
> > > >  drivers/usb/musb/da8xx.c    | 28 +++++++++++++++++++---------
> > > >  2 files changed, 31 insertions(+), 14 deletions(-)
> > >
> > > I have found another problem with peripheral mode. When we force
> > > peripheral mode, the glue layer currently uses CFGCHIP2 to override the
> > > VBUS and ID. This causes it to not be able to detect disconnection
> > > because the VBUS is overridden.
> How have you found it ? Does it cause any issues ?
> I mean I had to enable traces to see that disconnect was not happening.

I am also using the device tree patch series. I specified dr_mode = 
"peripheral" in my device tree because the device is only wired for use 
as a peripheral port.

I have actually known about this issue for a long time. See
<https://github.com/ev3dev/ev3dev/issues/244> and 
<http://e2e.ti.com/support/embedded/linux/f/354/p/65332/237094#2370942>


> > > Here is a patch to fix the problem. I have tested this on LEGO
> > > MINDSTORMS EV3 (AM1808). This works because the ID pin is internally
> > > pulled up on the SoC, so we don't need to override it.
> Actually, I'm wonder if that if not related to VBUS sensing.
> May be we should set CFGCHIP2_VBDTCTEN in device mode.

Yes, as we discussed in another thread, we should set CFGCHIP2_VBDTCTEN 
and CFGCHIP2_SESNDEN *always* regardless of mode. I still have the 
problem described above with these two enabled if and only if we are 
also setting CFGCHIP2_OTG_FORCE_PERIPHERAL.

> > > ---
> > >
> > > diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
> > > index 2bc12a2..33daa3b 100644
> > > --- a/drivers/usb/musb/da8xx.c
> > > +++ b/drivers/usb/musb/da8xx.c
> > > @@ -374,9 +374,7 @@ static int da8xx_musb_set_mode(struct musb *musb, u8
> > > musb_mode)
> > >         case MUSB_HOST:         /* Force VBUS valid, ID = 0 */
> > >                 phy_mode = PHY_MODE_USB_HOST;
> > >                 break;
> > > -       case MUSB_PERIPHERAL:   /* Force VBUS valid, ID = 1 */
> > > -               phy_mode = PHY_MODE_USB_DEVICE;
> > > -               break;
> > > +       case MUSB_PERIPHERAL:
> > >         case MUSB_OTG:          /* Don't override the VBUS/ID
> > > comparators */
> > >                 phy_mode = PHY_MODE_USB_OTG;
> > >                 break;
> > >
> > > ---
> > >
> > > If this works for other SoCs/boards, I think we should make this change.
> > > If it doesn't work, we could work around the VBUS problem by polling
> > > VBUSSENSE in CFGCHIP2. But, I like the simple solution above better.
> >
> > I have realized that due to the way my device is wired, I can actually
> > use OTG mode and it will behave exactly as peripheral mode because the
> > ID pin is not connected. So, maybe this patch is not needed after all.
> Actually, I'm sure that is related to ID

The ID pin on my device is not connected, so I don't think this has to 
do with ID. It is always high (internally pulled up).

> I have the same issue except the disconnect is called when I use the
> OTG mode.

This is exactly the behavior I am seeing.