linux-kernel - Re: [PATCH] gpio: zynq: Setup chip->base based on alias ID

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Message-ID: <8b344d48-592d-8be8-bea0-e29b3e8469a1@xilinx.com>
Date:   Tue, 15 May 2018 15:26:40 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Michal Simek <michal.simek@...inx.com>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michal Simek <monstr@...str.eu>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Peter Crosthwaite <peter.crosthwaite@...inx.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Rob Herring <robherring2@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] gpio: zynq: Setup chip->base based on alias ID

Hi Linus,

On 2.5.2018 16:19, Michal Simek wrote:
> On 2.5.2018 15:56, Linus Walleij wrote:
>> On Wed, May 2, 2018 at 3:41 PM, Michal Simek <michal.simek@...inx.com> wrote:
>>
>>> If you don't want this patch I understand that and it will become just
>>> another soc vendor patch out of mainline.
>>
>> I don't really know what to do, so that is why I'm discussing.
> 
> me too. It is also interesting that I have met with the case with
> zynq/zynqmp gpio driver and not gpio-xilinx.c which can have a lot of
> instances.
> 
>>
>> It's one of those gray areas.
>>
>> From one point of view there is the purist stance that we should
>> only support what the mainline tree does, and be strict and
>> consistent so we don't accumulate to many nasty hacks.
> 
> Also this expect that the first patch does everything right which is not
> truth all the time.
> 
>>
>> On the other hand, it is completely possible that all users of this
>> particular driver actually must have this patch, and then I just
>> push them to use a deviant vendor tree for no good reason.
>>
>> Would it be possible that I apply the patch, and somehow also
>> establish some understanding with all users of the Xilinx
>> platform that whatever legacy applications are out there
>> must start to migrate towards using the character device so
>> this reliance on the numberspace doesn't stick around forever?
> 
> When someone contacts me for asking guidance for gpio I am telling them
> not to use legacy sysfs interface and use libgpiod. Last one was a week
> ago in connection to Ultra96 and libmraa.
> 
> But even chardev is not supported there now.
> https://github.com/intel-iot-devkit/mraa/issues/713
> 
>>
>> For example can we make a patch to some systems like
>> arch/arm/boot/dts/zynq-*.dts
>> adding proper GPIO line names to these device trees, such
>> as was made in e.g. commit f6b1674d570aa1
>> "arm64: dts: qcom: sbc: Name GPIO lines"
> 
> If you take a look at
> arch/arm64/boot/dts/xilinx/zynqmp-zcu100-revC.dts
> which is Ultra96 board gpio-line-names are filled there for the whole PS
> part. Definitely take a look and let know if you find out any issue there.
> 
> zynq/zynqmp gpio controller contains PS pins (hard part) and PL pins
> coming to logic.
> 
> I can't describe PL gpio pins because it can be whatever even I have
> done that for one fixed hw design.
> 
> Interesting part on that sha1 you shared is how "NC" pin is described.
> 
> gpio pin 35 I have on zcu100 as "" but it should be maybe TP_PAD which
> is really just a pad on real board. And the rest of "" gpio names are
> connected to PL.
> 
> I am happy to take a look at existing platforms and use gpio-line-names
> there. For example arch/arm64/boot/dts/xilinx/zynqmp-zcu102-revA.dts
> I use in tca6416_u97 and u61 comments instead of this property.
> 

Have you done any decision about this patch?

Thanks,
Michal