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Message-ID: <b6180be5-5ae6-4671-8a2f-68ffa35dadbe@collabora.com>
Date: Tue, 10 Feb 2026 15:26:38 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: wens@...nel.org, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: David Lechner <david@...hnology.com>, Cathy Xu
<ot_cathy.xu@...iatek.com>, Matthias Brugger <matthias.bgg@...il.com>,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
Yong Mao <yong.mao@...iatek.com>, Wenbin Mei <Wenbin.Mei@...iatek.com>,
Axe Yang <Axe.Yang@...iatek.com>, Lei Xue <Lei.Xue@...iatek.com>
Subject: Re: [PATCH] arm64: dts: mediatek: mt8189: Add pinmux macro header
file
Il 10/02/26 13:48, Chen-Yu Tsai ha scritto:
> On Tue, Feb 10, 2026 at 7:03 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> Il 09/02/26 22:48, David Lechner ha scritto:
>>> On 9/18/25 9:03 PM, Cathy Xu wrote:
>>>> Add the pinctrl header file on MediaTek mt8189.
>>>>
>>>> Signed-off-by: Cathy Xu <ot_cathy.xu@...iatek.com>
>>>> ---
>>>> This patch is base on the patch series:
>>>> https://patchwork.kernel.org/project/linux-mediatek/list/?series=981475
>>>> [1] dt-bindings: pinctrl: mediatek: Add support for mt8189
>>>> [2] arm64: dts: mediatek: mt8189: Add pinmux macro header file
>>>> [3] pinctrl: mediatek: Add pinctrl driver on mt8189
>>>> Since patch [1] and [3] of the series have already been merged, this
>>>> patch(patch [2]) is being resent individually after modifications.
>>>> ---
>>>> arch/arm64/boot/dts/mediatek/mt8189-pinfunc.h | 1125 +++++++++++++++++
>>>> 1 file changed, 1125 insertions(+)
>>>> create mode 100644 arch/arm64/boot/dts/mediatek/mt8189-pinfunc.h
>>>>
>>>> diff --git a/arch/arm64/boot/dts/mediatek/mt8189-pinfunc.h b/arch/arm64/boot/dts/mediatek/mt8189-pinfunc.h
>>>> new file mode 100644
>>>> index 000000000000..df69f50c267a
>>>> --- /dev/null
>>>> +++ b/arch/arm64/boot/dts/mediatek/mt8189-pinfunc.h
>>>
>>> General question:
>>>
>>> Why do we have similar files in two different places different places?
>>>
>>> $ ls arch/arm64/boot/dts/mediatek/*-pin*
>>> arch/arm64/boot/dts/mediatek/mt2712-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt6878-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt6893-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt8167-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt8173-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt8196-pinfunc.h
>>> arch/arm64/boot/dts/mediatek/mt8516-pinfunc.h
>>>
>>> $ ls include/dt-bindings/pinctrl/mt*
>>> include/dt-bindings/pinctrl/mt65xx.h
>>> include/dt-bindings/pinctrl/mt6779-pinfunc.h
>>> include/dt-bindings/pinctrl/mt6795-pinfunc.h
>>> include/dt-bindings/pinctrl/mt6797-pinfunc.h
>>> include/dt-bindings/pinctrl/mt7623-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8135-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8183-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8186-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8192-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8195-pinfunc.h
>>> include/dt-bindings/pinctrl/mt8365-pinfunc.h
>>>
>>>
>>> Plus one different naming pattern.
>>>
>>> $ ls include/dt-bindings/pinctrl/mediatek,*
>>> include/dt-bindings/pinctrl/mediatek,mt8188-pinfunc.h
>>>
>>>
>>>
>>> Which one is preferred?
>>>
>>>
>> The MediaTek pinctrl must gain compatibility with standard pinctrl bindings. Until
>> then, bindings maintainers decided that these headers must go to the dts/mediatek
>> folder.
>>
>> It is my desire to (but lack of time on my side hits hard) do the right thing and
>> make the MediaTek pinctrl drivers to actually "understand" standard bindings.
>
> The headers encode the pin numbers and mux values in a way that the
> "pinmux" property requires, all the while giving them meaningful names.
>
> I suppose you could consider them part of the binding, as the pin controller
> binding assembles all the individual PIO blocks in the SoC to produce one
> unified view of all the pins. How they are ordered is important.
>
> Plus the datasheets are horrible to read, as the pins aren't always numbered,
> but are referred to using symbolic names like I2S2_MCLK.
>
>> I'd be - of course - happy if anyone else beats me on time (which wouldn't be hard
>> really) and pushes a series to fix this situation.
>>
>> Just to be clear - right now, the MTK pinctrl DT looks like:
>>
>> panel_default_pins: panel-default-pins {
>> pins-rst {
>> pinmux = <PINMUX_GPIO108__FUNC_GPIO108>;
>> output-high;
>> };
>>
>> pins-en {
>> pinmux = <PINMUX_GPIO48__FUNC_GPIO48>;
>> output-low;
>> };
>> };
>>
>> spi1_pins: spi1-pins {
>> pins {
>> pinmux = <PINMUX_GPIO136__FUNC_SPIM1_CSB>,
>> <PINMUX_GPIO137__FUNC_SPIM1_CLK>,
>> <PINMUX_GPIO138__FUNC_SPIM1_MO>,
>> <PINMUX_GPIO139__FUNC_SPIM1_MI>;
>> bias-disable;
>> };
>> };
>
> To be fair, the above is one valid kind of generic pinmux description.
>
> From Documentation/devicetree/bindings/pinctrl/pinmux-node.yaml :
>
> While not required to be used, there are 3 generic forms of pin muxing nodes
> which pin controller devices can use.
>
> For hardware where pin multiplexing configurations have to be specified for
> each single pin the number of required sub-nodes containing "pin" and
> "function" properties can quickly escalate and become hard to write and
> maintain.
>
> For cases like this, the pin controller driver may use the pinmux helper
> property, where the pin identifier is provided with mux configuration settings
> in a pinmux group. A pinmux group consists of the pin identifier and mux
> settings represented as a single integer or an array of integers.
>
> The pinmux property accepts an array of pinmux groups, each of them describing
> a single pin multiplexing configuration.
>
> - end quote -
>
> So Mediatek is following one of the generic pinmux bindings. It's not the
> only one using this scheme either. STM32 and some of the Renesas platforms
> also follow it.
>
Not saying that MediaTek is the only one that uses such bindings style, at all.
I admit I was too tough about that, but as of the current state, the *binding*
is not generic, and it's strictly tied to the GPIO Controller IP version of one
specific SoC.
While this style is generic, the actual pinmux *definitions* in the header are
not generic - that's what I wanted to say, and I admit I went a bit too vague
with words that are easy to misunderstand.
>> ....but the driver should gain compatibility with nodes which would look like:
>>
>> panel_default_pins: panel-default-pins {
>> pins-rst {
>> pins = "gpio108";
>> function = "gpio";
>> output-high;
>> };
>>
>> pins-en {
>> pins = "gpio48";
>> function = "gpio";
>> output-low;
>> };
>> };
>>
>> spi1_pins: spi1-pins {
>> pins-bus {
>> pins = "gpio136", "gpio137", "gpio138", "gpio139",
>> function = "spi_m1";
>
> Why is it "spi_m1", not "spi1"?
>
PINMUX_GPIO138__FUNC_SPIM1_MO -> s/PINMUX_GPIO138__FUNC_//g/ and s/_MO//g
M1 stands for "Master 1" - that's because technically there could be a different
pinfunc for SPI "Slave 1" function.
That's SoC-specific anyway, not all of them have SPIS1, not all of them need
a different function, and... you get the point, I'm sure :-)
>
> Honestly you likely don't want this, or rather you don't want a huge table
> of pins and pinmux values and strings in the kernel. It takes a lot of time
> to write, even more time to review, and takes up a lot of space for each
> pinctrl driver. And those are generally built-in.
>
> The Allwinner platform has gone in the reverse direction: instead of having
> a huge table, we put the mux value in the DT using a custom property.
> See the following for discussions:
>
> https://patchwork.ozlabs.org/project/linux-gpio/cover/20171113012523.2328-1-andre.przywara@arm.com/
> https://patchwork.ozlabs.org/project/linux-gpio/patch/20171113012523.2328-2-andre.przywara@arm.com/
>
> And this is what finally landed:
>
> https://lore.kernel.org/linux-gpio/20250306235827.4895-7-andre.przywara@arm.com/
>
> Has it caused a bit of trouble? Perhaps. I was working on various peripherals
> on a new board and put in the wrong mux value and didn't notice for a couple
> days.
>
Then we must find a way to decouple hardware-specific information from the actual
header I think?
Alternatively - that's what I have understood - and if I've understood that wrong,
this needs clarification from the bindings maintainers, and why they wanted the
MediaTek pinctrl bindings to get moved to arch/arm64/boot/dts/mediatek/ instead of
include/dt-bindings/pinctrl/
Bindings maintainers, any word on this?
Did I misunderstand anything in past reviews ... from krzk if I remember correctly?
Cheers,
Angelo
>
>
> ChenYu
>
>> bias-disable;
>> };
>> };
>>
>> .... or
>>
>> spi1_pins: spi1-pins {
>> pins-bus {
>> function = "spi_m1";
>> groups = "spi_m1_pins";
>> bias-disable;
>> };
>> };
>>
>> That's the entire situation.
>>
>> Cheers,
>> Angelo
>>
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