On Wed, Feb 25, 2009 at 11:36:27AM -0800, David Brownell wrote: > On Wednesday 25 February 2009, Felipe Balbi wrote: > > The default limits on vbus would cause strange behaviours > > on bus-powered musb-based devices. > > You actually have hardware that can run Linux from USB > suspend currents? I thought the only such hardware used > 8-bit microcontrollers. And that Nokia's devices have > batteries, and are thus "self" powered, not bus powered. > (Self powered doesn't mean "won't use VBUS".) I didn't express myself nicely. I meant devices that charge battery over usb. > Recall that such hardware must suspend at about 0.5 mA > current, though after enumeration into a "high power" > configuration (such as 500 mA) it could use 2.5 mA. > > > With a 500mA configuration, the vbus draw would not switch > > from 0 to 500, it would have one step in either 8mA or 100mA > > depending whether gadget have otg enabled or not. > > I don't follow. This function is called right after a USB > reset. No SET_CONFIGURATION has been done yet. It's just Exactly, which makes our device starts drawing 8mA (or 100mA if non-otg) even though the gadget driver didn't ask it to. > returning to the default state; no bug that I see. Once > the SET_CONFIGURATION is issued, it can use more current. what would happen in this case is that we would try to charge at 8mA and a few jiffies later we would have to change our charging profile to 500mA since we just got a high power configuration chosen. What I mean with this patch is that musb shouldn't try to figure default values for vbus_draw(); that should be the gadget driver's role to call usb_gadget_vbus_draw(), right ? Moreover, I don't see any other gadget controller driver calling their vbus_draw() function themselves. -- balbi -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
