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

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Message-ID: <a9054501-03ce-4db2-a753-81741c6237b6@pigmoral.tech>
Date: Tue, 23 Sep 2025 14:31:31 +0800
From: Junhui Liu <junhui.liu@...moral.tech>
To: Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
 Yixun Lan <dlan@...too.org>, Alex Elder <elder@...cstar.com>
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

Hi Troy,

On 9/23/25 10:59 AM, 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)
>>>
>>> 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?
>
> If it’s an index, should it start from 0 or 1?
> 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.
>
> Could you clarify this? Yixun.

I think the second number represents the index of the pin group available
for this device.

Take pwm14 as an example: according to the manual, the first pin group
(index 0) available for pwm14 is GPIO6 with function 3, while the second
group (index 1) is GPIO44 with function 4.

>                  - Troy

-- 
Best regards,
Junhui Liu