linux-kernel - Re: [PATCH v4 3/3] pinctrl: Add Xilinx ZynqMP pinctrl driver support

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Message-ID: <dabcfe43-568a-66c1-642e-eef065f9b5ab@xilinx.com>
Date:   Wed, 24 Mar 2021 10:02:53 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michal Simek <michal.simek@...inx.com>
CC:     Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@...inx.com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, <git@...inx.com>,
        <saikrishna12468@...il.com>
Subject: Re: [PATCH v4 3/3] pinctrl: Add Xilinx ZynqMP pinctrl driver support



On 3/24/21 9:49 AM, Greg Kroah-Hartman wrote:
> On Wed, Mar 24, 2021 at 09:29:12AM +0100, Michal Simek wrote:
>> On 3/23/21 2:42 PM, Greg Kroah-Hartman wrote:
>>> On Wed, Mar 17, 2021 at 01:55:16PM +0530, Sai Krishna Potthuri wrote:
>>>> Adding pinctrl driver for Xilinx ZynqMP platform.
>>>> This driver queries pin information from firmware and registers
>>>> pin control accordingly.
>>>>
>>>> Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@...inx.com>
>>>> ---
>>>>  drivers/pinctrl/Kconfig          |   13 +
>>>>  drivers/pinctrl/Makefile         |    1 +
>>>>  drivers/pinctrl/pinctrl-zynqmp.c | 1030 ++++++++++++++++++++++++++++++
>>>>  3 files changed, 1044 insertions(+)
>>>>  create mode 100644 drivers/pinctrl/pinctrl-zynqmp.c
>>>>
>>>> diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
>>>> index 815095326e2d..25d3c7208975 100644
>>>> --- a/drivers/pinctrl/Kconfig
>>>> +++ b/drivers/pinctrl/Kconfig
>>>> @@ -341,6 +341,19 @@ config PINCTRL_ZYNQ
>>>>  	help
>>>>  	  This selects the pinctrl driver for Xilinx Zynq.
>>>>  
>>>> +config PINCTRL_ZYNQMP
>>>> +	bool "Pinctrl driver for Xilinx ZynqMP"
>>>
>>> Please make this work as a module.
>>
>> The most of pinctrl drivers are builtin modules now which is not excuse
>> it is just fact.
>> $ git grep module_pla drivers/pinctrl/ | wc -l
>> 40
>> $ git grep  builtin_pla drivers/pinctrl/ | wc -l
>> 64
> 
> For new ones, we can do better, don't make us have to go back and fix
> this up later.

As I said not a big deal. If this is the way to go then I these rules
should be followed which is not what it is happening based on 3 latest
pinctrl drivers below.

> 
>> Also at least last 3 pinctrl drivers which have been merged are not modules.
>> d4c34d09ab03 ("pinctrl: Add RISC-V Canaan Kendryte K210 FPIOA driver")
>> 7e5ea974e61c ("pinctrl: pinctrl-microchip-sgpio: Add pinctrl driver for
>> Microsemi Serial GPIO")
>> a68a7844264e ("pinctrl: visconti: Add Toshiba Visconti SoCs pinctrl
>> support")
>>
>> None is saying that it can't be done but that cases where you use
>> pinctrl as module are really very limited. When you start to use pinctrl
>> and its functionality you need to have it as the part of the kernel to
>> be to get console, mmc, ethernet, usb, etc.
>>
>> That's why I would like to know what functionality and use case you have
>> in mind that this driver should be made module.
> 
> The "functionality" of building a kernel image that works on all
> hardware types.  Just like x86-64 has been for a very long time :)

ok.

Thanks,
Michal