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

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Date:   Mon, 26 Jun 2023 15:34:38 +0200
From:   neil.armstrong@...aro.org
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Dmitry Rokosov <ddrokosov@...rdevices.ru>
Cc:     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

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.

> 
>> 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.

> 
> [...]
>> +                               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