Martin,
On Sun, Jun 25, 2023 at 11:07:51PM +0200, Martin Blumenstingl wrote:
> On Wed, Jun 7, 2023 at 10:16 PM Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx> wrote:
> >
> > From: Oleg Lyovin <ovlevin@xxxxxxxxxxxxxx>
> >
> > The Amlogic A1 has a UART_AO port, which can be used, for example, for
> > BT HCI H4 connection.
> >
> > This patch adds mux definitions for it.
> In the past we've only taken the pinctrl definitions if we have a
> board that uses them.
> Neil, do we still have the same policy in place? If so this patch
> should be sent with the series that adds support for your A1 board.
>
> > Signed-off-by: Oleg Lyovin <ovlevin@xxxxxxxxxxxxxx>
> > Signed-off-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx>
> > ---
> > arch/arm64/boot/dts/amlogic/meson-a1.dtsi | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/amlogic/meson-a1.dtsi b/arch/arm64/boot/dts/amlogic/meson-a1.dtsi
> > index 0efd922ca7e1..3eb6aa9c00e0 100644
> > --- a/arch/arm64/boot/dts/amlogic/meson-a1.dtsi
> > +++ b/arch/arm64/boot/dts/amlogic/meson-a1.dtsi
> > @@ -118,6 +118,22 @@ gpio: bank@400 {
> > gpio-ranges = <&periphs_pinctrl 0 0 62>;
> > };
> >
> > + uart_a_pins: uart_a {
> Only our newer .dtsi (e.g. meson-g12-common.dtsi) are following the
> pattern where node names should use dashes instead of underscores.
> So please use: uart_a_pins: uart-a { ...
>
Okay, no problem. I'll rename the nodes in the next patch series
version.
> [...]
> > + uart_a_cts_rts_pins: uart_a_cts_rts {
> similar to the comment from above:
> uart_a_cts_rts_pins: uart-a-cts-rts { ...
>
Ok
> > + mux {
> > + groups = "uart_a_cts",
> > + "uart_a_rts";
> > + function = "uart_a";
> > + bias-pull-down;
> Out of curiosity: is this pull down needed on all boards or just specific ones?
> It seems like all other SoCs use bias-disable for the RTS/CTS pins.
>
That's a good question. The Amlogic custom kernel DTSI declares
bias-pull-down for CTS/RTS pins in UART_A. There is no information about
this in the A1 datasheet. However, from my understanding, it is related
to the usage of the UART_A. Typically, the UART_A endpoint on A1 boards
is used for BT connections, which is why Amlogic applies bias-pull-down
in the common DTSI. If my assumption is correct, it would be better to
move the bias-pull-down node parameter to the custom board DTS. I will
investigate this further and rework it in the next version if necessary.
--
Thank you,
Dmitry
