linux-kernel - Re: [PATCH v1 5/6] arm64: dts: meson: a1: introduce UART

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Date:   Wed, 28 Jun 2023 17:51:10 +0300
From:   Dmitry Rokosov <ddrokosov@...rdevices.ru>
To:     <neil.armstrong@...aro.org>
CC:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <jbrunet@...libre.com>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <khilman@...libre.com>,
        <conor+dt@...nel.org>, <kernel@...rdevices.ru>,
        <sdfw_system_team@...rdevices.ru>, <rockosov@...il.com>,
        <linux-amlogic@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Oleg Lyovin <ovlevin@...rdevices.ru>
Subject: Re: [PATCH v1 5/6] arm64: dts: meson: a1: introduce UART_AO mux
 definitions

Neil, Martin,

On Mon, Jun 26, 2023 at 03:34:38PM +0200, neil.armstrong@...aro.org wrote:
> Hi,
> 
> On 25/06/2023 23:07, Martin Blumenstingl wrote:
> > On Wed, Jun 7, 2023 at 10:16 PM Dmitry Rokosov <ddrokosov@...rdevices.ru> wrote:
> > > 
> > > From: Oleg Lyovin <ovlevin@...rdevices.ru>
> > > 
> > > 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.
> 
> Yes and no, if the work is done I'll take it, but yeah since upstream linux
> hates dead code, let's only define what's necessary.
> 

I'll prepare the patches for ad401 reference board, and share the in the
next patch series version.

> > 
> > > Signed-off-by: Oleg Lyovin <ovlevin@...rdevices.ru>
> > > Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
> > > ---
> > >   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 { ...
> 
> The new scheme which should be use should be:
> 
> uart_a_pins: uart-a-pins-state {
> 
> but it wasn't enforced in the pinctrl yaml pushed by heiner, but for sure
> no underscores in the node name.
> 

Okay, got it

> > 
> > [...]
> > > +                               uart_a_cts_rts_pins: uart_a_cts_rts {
> > similar to the comment from above:
> > uart_a_cts_rts_pins: uart-a-cts-rts { ...
> > 
> > > +                                       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.
> > 
> > 
> > Best regards,
> > Martin
> 

-- 
Thank you,
Dmitry