linux-kernel - Re: [PATCH v3 3/3] riscv: dts: spacemit: define a SPI controller node

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Message-ID: <78FF4A33F1D1916E+aNNhDuW28Ia6o8gm@troy-wujie14pro-arch>
Date: Wed, 24 Sep 2025 11:10:06 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Alex Elder <elder@...cstar.com>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
	Yixun Lan <dlan@...too.org>
Cc: broonie@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, ziyao@...root.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, paul.walmsley@...ive.com,
	palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr,
	p.zabel@...gutronix.de, spacemit@...ts.linux.dev,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] riscv: dts: spacemit: define a SPI controller node

On Tue, Sep 23, 2025 at 07:49:34AM -0500, Alex Elder wrote:
> On 9/22/25 9:59 PM, Troy Mitchell wrote:
> > On Tue, Sep 23, 2025 at 08:19:30AM +0800, Yixun Lan wrote:
> > > Hi Alex,
> > > 
> > > On 11:17 Mon 22 Sep     , Alex Elder wrote:
> > > > Define a node for the fourth SoC SPI controller (number 3) on
> > > > the SpacemiT K1 SoC.
> > > > 
> > > > Enable it on the Banana Pi BPI-F3 board, which exposes this feature
> > > > via its GPIO block:
> > > >    GPIO PIN 19:  MOSI
> > > >    GPIO PIN 21:  MISO
> > > >    GPIO PIN 23:  SCLK
> > > >    GPIO PIN 24:  SS (inverted)
> 
> Note that the pin numbers I'm mentioning above are the numbers
> (1-26) on the 26-pin GPIO header on the BPI-F3 board.
> 
> > > > 
> > > > Define pincontrol configurations for the pins as used on that board.
> > > > 
> > > > (This was tested using a GigaDevice GD25Q64E SPI NOR chip.)
> > > > 
> > > > Signed-off-by: Alex Elder <elder@...cstar.com>
> > > > ---
> > > > v3: - Moved the SPI controller into the dma-bus memory region
> > > > 
> > > >   .../boot/dts/spacemit/k1-bananapi-f3.dts      |  7 +++++++
> > > >   arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi  | 20 +++++++++++++++++++
> > > >   arch/riscv/boot/dts/spacemit/k1.dtsi          | 16 +++++++++++++++
> > > >   3 files changed, 43 insertions(+)
> > > > 
> > > > diff --git a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > > index 2aaaff77831e1..d9d865fbe320e 100644
> > > > --- a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > > +++ b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > > @@ -14,6 +14,7 @@ aliases {
> > > >   		ethernet0 = &eth0;
> > > >   		ethernet1 = &eth1;
> > > >   		serial0 = &uart0;
> > > > +		spi3 = &spi3;
> > > >   	};
> > > >   	chosen {
> > > > @@ -92,6 +93,12 @@ &pdma {
> > > >   	status = "okay";
> > > >   };
> > > > +&spi3 {
> > > > +	pinctrl-0 = <&ssp3_0_cfg>;
> > > > +	pinctrl-names = "default";
> > > > +	status = "okay";
> > > > +};
> > > > +
> > > >   &uart0 {
> > > >   	pinctrl-names = "default";
> > > >   	pinctrl-0 = <&uart0_2_cfg>;
> > > > diff --git a/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi b/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> > > > index aff19c86d5ff3..205c201a3005c 100644
> > > > --- a/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> > > > +++ b/arch/riscv/boot/dts/spacemit/k1-pinctrl.dtsi
> > > > @@ -76,4 +76,24 @@ pwm14-1-pins {
> > > >   			drive-strength = <32>;
> > > >   		};
> > > >   	};
> > > > +
> > > > +	ssp3_0_cfg: ssp3-0-cfg {
> > > ..
> > > > +		ssp3-0-no-pull-pins {
> > > I'd prefer not to enforce "pull" info inside the name, you can't embed
> > > all property info, besides, what's if you want to change/override later?
> > > 
> > > how about just name it as ssp3-0-defaul-pins or simply ssp3-0-pins?
> > uart: uart0_2_cfg and function is 2.
> > pwm: pwm14_1_cfg and function is 4
> > spi: ssp3_0_cfg and function is 2
> > 
> > I’m a bit confused about the meaning of the second number here.
> > Is it intended to be an index, or the function number?
> 
> It is an index, and it seems arbitrary but it is based on the
> order in which they occur in a spreadsheet that defines a set
> of possible pin configurations.
> 
> For example, SPI3 lists 2 possible pin combinations:
> SCLK	GPIO[75] function 2	GPIO[59] function 2
> FRM	GPIO[76] function 2	GPIO[60] function 2
> TXD	GPIO[77] function 2	GPIO[61] function 2
> RXD	GPIO[78] function 2	GPIO[62] function 2
> 
> > If it’s an index, should it start from 0 or 1?
> 
> It starts with 0.
> 
> > The starting point seems inconsistent across pwm/spi/uart.
> > If it’s supposed to be the function number,
> > then the spi and pwm parts look incorrect.
> 
> The first one (index 0) shows up earlier (lower line number) in
> the spreadsheet, even though the GPIO numbers used are higher
> than those in the second one.  They're grouped, and the first
> one is in GPIO group 2 and the second is in GPIO group 5.
Thanks! It makes sense.

                - Troy

> 
> 					-Alex
> 
> > Could you clarify this? Yixun.
> > 
> >                  - Troy
> > > 
> > > > +			pinmux = <K1_PADCONF(75, 2)>,	/* SCLK */
> > > > +				 <K1_PADCONF(77, 2)>,	/* MOSI  */
> > > > +				 <K1_PADCONF(78, 2)>;	/* MISO */
> > > > +
> > > > +			bias-disable;
> > > > +			drive-strength = <19>;
> > > > +			power-source = <3300>;
> > > > +		};
> > > > +
> > > > +		ssp3-0-frm-pins {
> > > > +			pinmux = <K1_PADCONF(76, 2)>;	/* FRM (frame) */
> > > > +
> > > > +			bias-pull-up = <0>;
> > > > +			drive-strength = <19>;
> > > > +			power-source = <3300>;
> > > > +		};
> > > > +	};
> > > >   };
> > > > diff --git a/arch/riscv/boot/dts/spacemit/k1.dtsi b/arch/riscv/boot/dts/spacemit/k1.dtsi
> > > > index 6cdcd80a7c83b..eb8a14dd72ea4 100644
> > > > --- a/arch/riscv/boot/dts/spacemit/k1.dtsi
> > > > +++ b/arch/riscv/boot/dts/spacemit/k1.dtsi
> > > > @@ -797,6 +797,22 @@ uart9: serial@...17800 {
> > > >   				status = "disabled";
> > > >   			};
> > > > +			spi3: spi@...1c000 {
> > > > +				compatible = "spacemit,k1-spi";
> > > > +				reg = <0x0 0xd401c000 0x0 0x30>;
> > > > +				#address-cells = <1>;
> > > > +				#size-cells = <0>;
> > > > +				clocks = <&syscon_apbc CLK_SSP3>,
> > > > +					 <&syscon_apbc CLK_SSP3_BUS>;
> > > > +				clock-names = "core", "bus";
> > > > +				resets = <&syscon_apbc RESET_SSP3>;
> > > > +				interrupts = <55>;
> > > ..
> > > > +				dmas = <&pdma 20>,
> > > > +				       <&pdma 19>;
> > > can we also squash the dmas into one line? but, do split if there are too many..
> > > 
> > > yes, it's simply a style change that I'd like to keep them consistent at DT level,
> > > besides you might also want to adjust dt-binding examples to align with them here..
> > > 
> > > thanks
> > > 
> > > > +				dma-names = "rx", "tx";
> > > > +				status = "disabled";
> > > > +			};
> > > > +
> > > >   			/* sec_uart1: 0xf0612000, not available from Linux */
> > > >   		};
> > > > -- 
> > > > 2.48.1
> > > > 
> > > > 
> > > 
> > > -- 
> > > Yixun Lan (dlan)
> > > 
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> 
>

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