Re: [Linux-stm32] [PATCH 07/22] ARM: dts: stm32: Add alternate pinmux for SDMMC2 pins 4-7

From: Marek Vasut <marex@denx.de>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>,
	Patrice CHOTARD <patrice.chotard@st.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Patrick DELAUNAY <patrick.delaunay@st.com>,
	"linux-stm32@st-md-mailman.stormreply.com"
	<linux-stm32@st-md-mailman.stormreply.com>
Subject: Re: [Linux-stm32] [PATCH 07/22] ARM: dts: stm32: Add alternate pinmux for SDMMC2 pins 4-7
Date: Mon, 30 Mar 2020 13:45:30 +0200	[thread overview]
Message-ID: <97d13a84-8220-aa7f-3ee6-df474cca3882@denx.de> (raw)
In-Reply-To: <310aa3a3-09ce-42ef-d1ea-b653163d1d72@pengutronix.de>

On 3/30/20 1:37 PM, Ahmad Fatoum wrote:
> Hi Marek,

Hi,

> On 3/30/20 1:22 PM, Marek Vasut wrote:
>> On 3/30/20 1:17 PM, Ahmad Fatoum wrote:
>>> Hello Patrice,
>>
>> Hi,
>>
>>> On 3/30/20 1:11 PM, Patrice CHOTARD wrote:
>>>> For your information, another submitted patch uses the same pinctrl sdmmc2_d47_pins_b node with different muxing (SDMMC2_D5)
>>>>
>>>> see https://lore.kernel.org/patchwork/patch/1216452/
>>>>
>>>> I haven't checked other muxing if there are other conflict.
>>>
>>> (author of linked patch here)
>>>
>>> I don't like the central stm32mp15-pinctrl.dtsi. I'd have preferred if each
>>> file defined the pinctrl groups it is using.
>>
>> I'm not a big fan of that either, because this is gonna be a
>> combinatorial explosion of various pinmux options. But if you have each
>> board define it's pinmux, it's also gonna become a massive amount of
>> duplication (like iMX). So I cannot tell which one is better ...
> 
> Mhm. A middle ground could be keeping stm32mp15-pinctrl, but only for the
> official ST eval kits as HW designers are expected to copy off those and have
> board specifics in the board/SoM device tree?

Then you should call it stm32mp1-something-st-eval-pinmux.dtsi ,
otherwise it's gonna be confusing.

> If it has to be either one or the other, I prefer duplication in the device
> tree. When the HW misses pull ups or needs to adjust slew rates, you probably
> don't want a new, slightly different, pinctrl group in the stm32mp15-pinctrl.dtsi
> for each variant.

That's a valid point, but then you can override those in the boards'
pinmux node for a specific pinmux entry too.

> So you are left with doctoring around with overrides and /delete-property/,
> while just duplicating the node with the correct properties would've been
> better for readability IMO.

That is true, but how many of such cases do we have so far ? Maybe it's
better to cross that bridge when (if) we come to it.

-- 
Best regards,
Marek Vasut

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