linux-kernel - Re: [PATCH 3/3] arm64: dts: rockchip: Enable UART8 on rock-3b

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Message-ID: <9330ebb370780c001fd2aaee49aec9e8@manjaro.org>
Date: Tue, 12 Nov 2024 16:07:10 +0100
From: Dragan Simic <dsimic@...jaro.org>
To: Tamás Szűcs <tszucs@...ux.com>
Cc: Jonas Karlman <jonas@...boo.se>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>, FUKAUMI Naoki
 <naoki@...xa.com>, Chukun Pan <amadeus@....edu.cn>,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: rockchip: Enable UART8 on rock-3b

Hello Tamas,

On 2024-11-12 15:35, Tamás Szűcs wrote:
> I agree; it's not possible to tell if the user will use a PCIe/USB,
> PCIe/UART, SDIO/UART, perhaps USB/UART device, or any other HIF
> combination. The way I see it is UART8 is hardwired to the M2E, so
> there is a reasonable expectation that it should work too if need be.

Please correct me if I'm wrong, but isn't this UART supposed to be
used for the Bluetooth part of an SDIO WiFi + Bluetooth module, in
form of a non-standard M.2 module that Radxa sells?

With that in mind, I see very little sense in just enabling the UART,
without defining the entire Bluetooth interface, which AFAIK produces
nasty looking error messages in the kernel log when there's actually
nothing connected to the UART.

As a side note, please use inline replying. [*]

[*] https://en.wikipedia.org/wiki/Posting_style

> On Mon, Nov 11, 2024 at 8:12 PM Jonas Karlman <jonas@...boo.se> wrote:
>> 
>> Hi Tamás,
>> 
>> On 2024-11-11 19:17, Tamás Szűcs wrote:
>> > Enable UART lines on Radxa ROCK 3 Model B M.2 Key E.
>> >
>> > Signed-off-by: Tamás Szűcs <tszucs@...ux.com>
>> > ---
>> >  arch/arm64/boot/dts/rockchip/rk3568-rock-3b.dts | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/arch/arm64/boot/dts/rockchip/rk3568-rock-3b.dts b/arch/arm64/boot/dts/rockchip/rk3568-rock-3b.dts
>> > index b7527ba418f7..61d4ba2d312a 100644
>> > --- a/arch/arm64/boot/dts/rockchip/rk3568-rock-3b.dts
>> > +++ b/arch/arm64/boot/dts/rockchip/rk3568-rock-3b.dts
>> > @@ -732,7 +732,7 @@ &uart8 {
>> >       pinctrl-names = "default";
>> >       pinctrl-0 = <&uart8m0_xfer &uart8m0_ctsn &uart8m0_rtsn>;
>> >       uart-has-rtscts;
>> > -     status = "disabled";
>> > +     status = "okay";
>> 
>> This should probably be enabled using an dt-overlay, there is no UART
>> device embedded on the board and the reason I left it disabled in
>> original board DT submission.
>> 
>> On second thought maybe they should be enabled, think PCIe and USB 
>> lines
>> on the M.2 Key E is already enabled by default. I probably only tested
>> with a pcie/usb wifi/bt card and not a sido/uart wifi/bt card.
>> 
>> >  };
>> >
>> >  &usb_host0_ehci {