linux-kernel - Re: [PATCH v3] riscv: dts: spacemit: add UART pinctrl combinations

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Message-ID: <20250917012941-GYA1263349@gentoo.org>
Date: Wed, 17 Sep 2025 09:29:41 +0800
From: Yixun Lan <dlan@...too.org>
To: Hendrik Hamerlinck <hendrik.hamerlinck@...mernet.be>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	alex@...ti.fr, skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] riscv: dts: spacemit: add UART pinctrl combinations

Hi Hendrik,

On 08:47 Tue 16 Sep     , Hendrik Hamerlinck wrote:
> Add UART pinctrl configurations based on the SoC datasheet and the
> downstream Bianbu Linux tree. The drive strength values were taken from
> the downstream implementation, which uses medium drive strength.
> CTS/RTS are moved to separate *-cts-rts-cfg states so boards can enable
> hardware flow control conditionally.
> 
> Signed-off-by: Hendrik Hamerlinck <hendrik.hamerlinck@...mernet.be>
> ---
> Changes in v3:
> - Added /omit-if-no-ref/ to pinctrl states to reduce DT size
> 
> Changes in v2:
> - Split cts/rts into separate pinctrl configs as suggested
> - Removed options from board DTS files to keep them cleaner
> ---
>  arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi | 432 ++++++++++++++++++-
>  1 file changed, 429 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi b/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> index 381055737422..7811fb485bd4 100644
> --- a/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> +++ b/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> @@ -11,12 +11,438 @@
>  #define K1_GPIO(x)	(x / 32) (x % 32)
>  
>  &pinctrl {
> +	/omit-if-no-ref/
> +	uart0_0_cfg: uart0-0-cfg {
> +		uart0-0-pins {
> +			pinmux = <K1_PADCONF(104, 3)>,	/* uart0_txd */
> +				 <K1_PADCONF(105, 3)>;	/* uart0_rxd */
> +			power-source = <3300>;
> +			bias-pull-up;
> +			drive-strength = <19>;
> +		};
> +	};
> +
> +	/omit-if-no-ref/
> +	uart0_1_cfg: uart0-1-cfg {
> +		uart0-1-pins {
> +			pinmux = <K1_PADCONF(108, 1)>,	/* uart0_txd */
> +				 <K1_PADCONF(80, 3)>;	/* uart0_rxd */
> +			power-source = <3300>;
..
> +			bias-pull-up;
here, see comment below
> +			drive-strength = <19>;
> +		};
> +	};
> +
> +	/omit-if-no-ref/
>  	uart0_2_cfg: uart0-2-cfg {
>  		uart0-2-pins {
> -			pinmux = <K1_PADCONF(68, 2)>,
> -				 <K1_PADCONF(69, 2)>;
> +			pinmux = <K1_PADCONF(68, 2)>,	/* uart0_txd */
> +				 <K1_PADCONF(69, 2)>;	/* uart0_rxd */
> +			bias-pull-up;
> +			drive-strength = <32>;
> +		};
> +	};
>  
> -			bias-pull-up = <0>;

Sorry, I've overlooked this, the bias-pull-up need to explicitly set to
a vale of 0, 1 - normal pull up, or strong pull up.. for uart, the normal
pull up should be ok

please refer Documentation/devicetree/bindings/pinctrl/spacemit,k1-pinctrl.yaml

Since the rc6 is already tagged, I'm about to prepare a PR, so If you able 
to respin a new version quickly, I'd be happy to take, otherwise let's wait
for next merge window (which shouldn't be a big problem)

btw, please always do a DT check: 
  make ARCH=riscv dtbs_check W=1

-- 
Yixun Lan (dlan)