Hello,
On Mon, Apr 03, 2017 at 03:25:23PM -0500, Rob Herring wrote:
> On Mon, Apr 3, 2017 at 10:01 AM, Fabio Estevam <festevam@xxxxxxxxx> wrote:
> > Hi Uwe,
> >
> > On Wed, Jul 13, 2016 at 6:01 AM, Uwe Kleine-König
> > <u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
> >> A part of my machine looks as follows (simplified):
> >>
> >> ,------------------------.
> >> | ,---------. |
> >> | | imx25 o--RX----◁---o---
> >> | | o--GPIO--' |
> >> | `---------' |
> >> `------------------------'
> >>
> >> that is, there is a driver on the RX line that must be enabled before
> >> the UART can be used. (That is necessary because the default mux of the
> >> RX pad after reset is an output.)
> >>
> >> To represent this in the device tree I do:
> >>
> >> pinctrl_uart5: uart5 {
> >> fsl,pins = <
> >> ...
> >> MX25_PAD_LBA__UART5_RXD 0x00000000
> >> MX25_PAD_CS5__GPIO_3_21 0x00002001
> >> ...
> >> };
> >>
> >> &uart5 {
> >> pinctrl-names = "default";
> >> pinctrl-0 = <&pinctrl_uart5>;
> >>
> >> enable-gpio = <&gpio3 21 GPIO_ACTIVE_LOW>;
>
> enable-gpios
ack.
> I imagine you already know this needs documentation. Make it common please.
Sure, I first wanted to collect some feedback to get an idea if this
would be accepted at all.
The only candidate for common code to add this functionality would be
uart_add_one_port. I wonder if this is early enough in every case.
> >> ...
> >> };
> >>
> >> This way it's ensured that the gpio is only enabled when the LBA pad is
> >> muxed as RX (together with the bootloader that sets the GPIO high).
> >>
> >> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> >
> > Since this is not imx serial specific it could be made more generic.
> >
> > What about extending
> > Documentation/devicetree/bindings/serial/slave-device.txt to handle
> > this GPIO, or maybe a regulator?
I could add a regulator that would do the right thing, that would not
match the hardware though.
> This is more like a phy than a device you talk to. It could also be
> something like an RS-232 xcvr enable (no one has done that already?).
> I think it belongs in the uart's node. You could additionally have an
> enable-gpios for a slave device.
Yes, I agree here, it is better defined in the uart's node, not in the
slave node.
Is xcvr-enable-gpios or xceiver-enable-gpios a better name?
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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