[PATCH 3/9] USB: add devicetree helpers for determining dr_mode and phy_type

[s.hauer@pengutronix.de (Sascha Hauer)]

On Thu, Feb 14, 2013 at 03:10:15PM +0200, Felipe Balbi wrote:
> On Thu, Feb 14, 2013 at 12:24:49PM +0100, Sascha Hauer wrote:
> > On Thu, Feb 14, 2013 at 12:15:10PM +0200, Felipe Balbi wrote:
> > > Hi,
> > > 
> > > On Thu, Feb 14, 2013 at 11:07:22AM +0100, Sascha Hauer wrote:
> > > > > > >> @@ -32,4 +35,37 @@ const char *usb_speed_string(enum usb_device_speed speed)
> > > > > > >>  }
> > > > > > >>  EXPORT_SYMBOL_GPL(usb_speed_string);
> > > > > > >>  
> > > > > > >> +#ifdef CONFIG_OF
> > > > > > >> +static const char *usb_dr_modes[] = {
> > > > > > >> +	[USB_DR_MODE_UNKNOWN]		= "",
> > > > > > >> +	[USB_DR_MODE_HOST]		= "host",
> > > > > > >> +	[USB_DR_MODE_PERIPHERAL]	= "peripheral",
> > > > > > >> +	[USB_DR_MODE_OTG]		= "otg",
> > > > > > >> +};
> > > > > > > 
> > > > > > > It turns out this is a problem, especially since this is generic usb
> > > > > > > code: we have a chipidea controller (a patchset just arrived) that does
> > > > > > > both host and peripheral, but not otg. And I'm told now that dwc3
> > > > > > > controller can be synthesized like that too.
> > > > > 
> > > > > I wonder if this part is really necessary. Usually you would read it
> > > > > from HW's registers. For dwc3, it's quite recently that we allowed the
> > > > > driver to be built with host-only, device-only or DRD functionality.
> > > > 
> > > > We have quite some boards on which the ID pin is not wired up, so if a
> > > > core is both host and device capable there is no way to detect the
> > > > wanted mode if not given from the devicetree.
> > > 
> > > right, that's fair. But that doesn't mean board can't work as both,
> > > right. The IP is still the same, just the board is wired differently ;-)
> > 
> > Yes, it is. Usually I run kernels with both host and device support enabled.
> > Consider the IP is OTG capable, the chipidea driver will initialize
> > both roles. Now if a board only supports one role and does not have an
> > ID pin, how do I make sure the driver is in the correct mode? I need to
> > specify it somehow. Otherwise I may end up on a host-only board with the
> > driver sitting in device mode, or with a device-only board with the
> > driver sitting in host mode.
> 
> right.
> 
> > > > > Maybe we can ignore dr_mode in host-only and device-only builds and only
> > > > > look at it for DRD builds ?
> > > > 
> > > > If something is or is not compiled in the kernel this doesn't mean the kernel
> > > > is not started on boards with a different situation.
> > > 
> > > who said kernel wouldn't start ? If you request a host-only build, you
> > > need to force your IP into working as host, since that's all you have,
> > > either that or you bail out on probe().
> > 
> > Let me clarify, I don't want to use Kconfig to specify my boards
> > capabilities. If a kernel is compiled for host mode only and the
> > devicetree specifies a port is device-only, then yes, the driver
> > should bail out on probe, maybe leaving a message that it found
> > a device for which the suitable role is not compiled in.
> 
> yeah, this is why I said we should ignore dr_mode (or bail out) when
> !OTG.

Ok, that's what the patch effectively does. We have this in chipidea/core.c:

| 	dr_mode = ci->platdata->dr_mode;
| 	if (dr_mode == USB_DR_MODE_UNKNOWN)
| 		dr_mode = USB_DR_MODE_OTG;

default to otg if nothing specified.

| 
| 	/* initialize role(s) before the interrupt is requested */
| 	if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_HOST) {
| 		ret = ci_hdrc_host_init(ci);
| 		if (ret)
| 			dev_info(dev, "doesn't support host\n");
| 	}

If we can do OTG or host, try to initialize host role,

| 
| 	if (dr_mode == USB_DR_MODE_OTG || dr_mode == USB_DR_MODE_PERIPHERAL) {
| 		ret = ci_hdrc_gadget_init(ci);
| 		if (ret)
| 			dev_info(dev, "doesn't support gadget\n");
| 	}

if we can do otg or peripheral, try to initialize device role,

| 
| 	if (!ci->roles[CI_ROLE_HOST] && !ci->roles[CI_ROLE_GADGET]) {
| 		dev_err(dev, "no supported roles\n");
| 		ret = -ENODEV;
| 		goto rm_wq;
| 	}

If we have no roles, complain and bail out.

ci_hdrc_host_init / ci_hdrc_gadget_init are static inline noops when
gadget or host are disabled.

Sascha

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