On Wed, Aug 16, 2017 at 2:06 PM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > * Liam Breck <liam@xxxxxxxxxxxxxxxxx> [170816 13:11]: >> On Wed, Aug 16, 2017 at 8:47 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: >> > * Liam Breck <liam@xxxxxxxxxxxxxxxxx> [170812 12:00]: >> >> On Sat, Aug 12, 2017 at 9:42 AM, Sebastian Reichel <sre@xxxxxxxxxx> wrote: >> >> > On Fri, Aug 11, 2017 at 02:57:10PM -0700, Liam Breck wrote: >> >> >> >> +Other features: >> >> >> >> +- Use gpio-hog to set the OTG pin high to enable 500mA charge current on USB SDP port. >> >> >> > >> >> >> > Why doesn't the charger driver control this? >> >> >> >> >> >> This pin/gpio has to be high when USB is plugged in to make the >> >> >> charger chip negotiate 500mA from a SDP port. It should generally be >> >> >> configured that way even if the driver is not loaded, as the chip does >> >> >> not require a driver to function. Some boards may do that with a >> >> >> pull-up. Also the user may want to change this via sysfs and not have >> >> >> the driver "fix" it. >> >> > >> >> > drivers/power/supply/qcom_smbb.c exposes the otg feature as >> >> > regulator. I think in this case it could be exposed as >> >> > gpio-regulator. >> >> >> >> Hans is doing that here: >> >> https://patchwork.kernel.org/patch/9883717/ >> >> >> >> The datasheet labels one pin "OTG" but that's misleading; it really >> >> enables negotiation of 500mA input current, but does not turn on OTG >> >> mode. If this pin is low, it only prevents the driver from starting >> >> OTG mode via I2C msg. >> > >> > Yeah so before the device has enumerated this pin keeps the >> > max current at 100mA as required by the USB spec. This pin >> > should be only toggled after enumerating in bootloader or >> > by the kernel driver. I tink the USB PHY driver can also >> > be wired to control this line. >> > >> > Probably best to set it up as just a GPIO that the bq24190 >> > driver controls optionally. >> > >> > Then later on we should have some Linux generic way for >> > USB gadget subsystem to tell the charger that we have >> > enumerated, and then bq24190 driver can toggle this GPIO >> > to enable higher charge rates. >> >> I discovered a few months ago that setting this pin high after USB >> connect has NO effect on iinlim. It has to be high at connect to >> auto-negotiate 500mA. There is no point in making the driver control >> this pin; we already tried that. >> >> Here we are just documenting how the DT can enable this pin via gpio-hog. > > Or in bootloader. Yeah this is mostly for completely empty > battery to start charging at 100mA until bootloader can start > and enable higher rates. > >> I believe the only way to defer 500mA negotiation is to leave this pin >> off and set iinlim via I2C msg to chip. We can do that in a gadget >> script via sysfs input_current_limit. Hans does not have to enable >> this pin to start OTG-host on his x86 device, perhaps because it is >> wired high there. Our script can set the linked gpio high if nec for >> OTG-host. > > Yeah once something is running? I haven't tried OTG-host on the anvl yet since it requires a special cable. > If the kernel does not need to do anything about it, how about > just leave it out of the binding docs then? It seemed useful to document the OTG pin DT config for boards that have it wired to a gpio... Is that not wise? -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
