[U-Boot] Doubt in USB driver for Vybrid vf610

[maitysanchayan at gmail.com]

On 15-10-24 18:16:20, Marek Vasut wrote:
> On Saturday, October 24, 2015 at 06:08:57 PM, maitysanchayan at gmail.com wrote:
> > On 15-10-24 18:08:53, Marek Vasut wrote:
> > > On Saturday, October 24, 2015 at 05:23:05 PM, maitysanchayan at gmail.com 
> wrote:
> > > > Hello,
> > > > 
> > > > On 15-10-24 12:09:43, Fabio Estevam wrote:
> > > > > Hi Marek,
> > > > > 
> > > > > On Fri, Oct 23, 2015 at 4:23 PM, Marek Vasut <marex at denx.de> wrote:
> > > > > >> Any inputs on the below?
> > > > > > 
> > > > > > I don't have a Vybrid device, CCing Fabio.
> > > > > 
> > > > > I don't have access to a Vybrid board either.
> > > > > 
> > > > > Sanchayan,
> > > > > 
> > > > > Does drivers/usb/host/ehci-mx6.c behave the same way?
> > > > 
> > > > No.
> > > > 
> > > > I included the particular piece of code below
> > > > 
> > > > 	if (init == USB_INIT_DEVICE && index == 1)
> > > > 	
> > > > 		return -ENODEV;
> > > > 	
> > > > 	if (init == USB_INIT_HOST && index == 0)
> > > > 	
> > > > 		return -ENODEV;
> > > > 
> > > > in the ehci-vf driver because our requirement was to have one port
> > > > as client and other as host. Since on USB start both ports get
> > > > configured as host as it iterates depending on USB EHCI controller
> > > > count, the above was meant to stop the port required as client to be
> > > > configured as host and vice versa while using client functionality
> > > > such as DFU.
> > > > 
> > > > I made the mistake of not thinking that this is not a generic use case,
> > > > someone might want it the other way around or such.
> > > > 
> > > > So coming to the main question, what would be the correct way to fix
> > > > this? I tested that even if the above four lines are removed and USB
> > > > start configures both ports as host, calling dfu later will still
> > > > result in correct functioning. So is this ok and the four lines should
> > > > be nuked or a more appropriate way would be to add something like
> > > > board_ehci_hcd_init_with_type(int index, enum usb_init _type init)
> > > > which would be a weak function and have the board specific code call
> > > > this to do the above which is currently done in ehci-vf.
> > > > 
> > > > I wasn't sure about the right approach to take so I asked.
> > > 
> > > Brief glare over the driver tells me that those four lines are complete
> > > nonsense and should be removed.
> > 
> > Yes very much so. But is removing just ok or it would be better to actually
> > restrict as per a board's requirement what gets configured as host and what
> > gets configured as client by adding the weak function hook I was talking
> > about?
> 
> The mx6 ones does board_usb_phy_mode() to determine this restriction. But (!)
> it'd be even better if this information was obtained from DT. It'd be nice
> if someone started working on converting i.MX to DT.

Yes, that's how iMX6 does it. However note that Vybrid USB is not a true OTG.

I quote the Vybrid TRM here,

"The USB is not a true OTG. It can be configured by software to function either
as a peripheral or as host. The ID pin, which is unique for OTG operation, is
not present in this implementation. There are no five pin interface. The user
will get four pin host/device interface."

As per 44.2.1.2 of the Vybrid TRM.

- Sanchayan.