linux-kernel - Re: [RESEND RFC PATCH 0/2] fixing the gpio ownership

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Message-ID: <20180118151211.GW2989@rfolt0960.corp.atmel.com>
Date:   Thu, 18 Jan 2018 16:12:11 +0100
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>
Subject: Re: [RESEND RFC PATCH 0/2] fixing the gpio ownership

On Thu, Jan 18, 2018 at 11:16:44AM +0100, Linus Walleij wrote:
> Hi Ludovic, thanks for your patches!
> 
> On Mon, Jan 15, 2018 at 5:24 PM, Ludovic Desroches
> <ludovic.desroches@...rochip.com> wrote:
> 
> > A few weeks ago, I have sent an RFC about adding bias support for GPIOs [1].
> 
> I was confused I think, because the issue of ownership and adding
> bias support were conflated.
> 

No problem, at the beginning, I only wanted to enable the strict. Doing
this involves that I have to remove pinctrl nodes for the pins which are
going to be request through the gpiolib to avoid conflicts. These pins
were configured with bias-pull-up. That's why I try to add the bias
support.

> I think I discussed properly the ideas I have for pin control properties
> vs the GPIOlib API/ABI in my response to patch 1.
> 

Thanks for the detailed answer about what you have in mind.

> > It was motivated by the fact that I wanted to enable the pinmuxing strict mode
> > for my pin controller which can muxed a pin as a peripheral or as a GPIO.
> 
> So that is a different thing from bias support.
> 

Well, yes and not! As a consequence of enabling strict mode, I have to
find another way to configure the pins.

> > Enabling the strict mode prevents several devices to be probed because
> > requesting a GPIO fails. The pin request function complains about the
> > ownership of the GPIO which is different from the mux ownership. I have to
> > remove my pinctrl node to avoid this conflict but I need it to configure my
> > pins and to set a pull-up bias for my GPIOs.
> 
> Okay I think the right solution is to fix the ownership issue, and set
> up bias using pin control/config but use the line through gpiolib for now.
> 
> > The main issue is that enabling the strict mode will
> > break old DTBs.
> 
> Yeah we need to work around that.
> 
> > I was going to submit patches for this but, after using the
> > sysfs which still show me a bad ownership, I decided that it should be fixed.
> 
> Yep :)
> 
> > So I did these patches. Unfortunately, there are several ways to lead to
> > gpiod_request(). It does the trick only for the gpiod_get family. The issue is
> > still present with legacy gpio_request and fwnode_get_named_gpiod.
> 
> fwnode_get_named_gpiod() must really be fixed too. You probably
> want to have things like LEDs and GPIO keys working even if
> your pin controller is strict.
> 

Yes, I have noticed this issue.

> I don't care so much about the old functions, I guess you just have
> to make sure that the drivers for *your* pin controller all use descriptors
> so that you can enable strict mode on *your* pin controller, right?
> 

Right, I have spotted some drivers to fix.

> Restrict your task to this, I'd say.
> 
> > It seems
> > that more and more drivers are converted to use GPIO descriptors so there is
> > some hope.
> 
> Yeah I'm doing this when I have time. There is plenty of work...
> Help appreciated.
> 

I will try to handle the ones related to the platforms I am using.

Regards

Ludovic