linux-kernel - Re: [RESEND PATCH v8 06/10] serial: sc16is7xx: fix regression with GPIO configuration

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Message-Id: <20230722104724.ef0c5896c239e721794b9fe9@hugovil.com>
Date:   Sat, 22 Jul 2023 10:47:24 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     gregkh@...uxfoundation.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, jirislaby@...nel.org, jringle@...dpoint.com,
        isaac.true@...onical.com, jesse.sung@...onical.com,
        tomasz.mon@...lingroup.com, l.perczak@...lintechnologies.com,
        linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>,
        stable@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Lech Perczak <lech.perczak@...lingroup.com>
Subject: Re: [RESEND PATCH v8 06/10] serial: sc16is7xx: fix regression with
 GPIO configuration

On Fri, 21 Jul 2023 13:24:19 -0600
Rob Herring <robh+dt@...nel.org> wrote:

> On Fri, Jul 21, 2023 at 10:19 AM Hugo Villeneuve <hugo@...ovil.com> wrote:
> >
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> >
> > Commit 679875d1d880 ("sc16is7xx: Separate GPIOs from modem control lines")
> > and commit 21144bab4f11 ("sc16is7xx: Handle modem status lines")
> > changed the function of the GPIOs pins to act as modem control
> > lines without any possibility of selecting GPIO function.
> 
> Requiring a new DT property is not fixing a kernel regression. You
> should be returning the kernel to original behavior and then have a
> new DT property for new behavior.

Hi Rob,
please read the entire patch history starting from V1
 and you will understand why this course of action was
 not selected.

 
> > As a consequence, applications that depends on GPIO lines configured
> > by default as GPIO pins no longer work as expected.
> >
> > Also, the change to select modem control lines function was done only
> > for channel A of dual UART variants (752/762). This was not documented
> > in the log message.
> >
> > Allow to specify GPIO or modem control line function in the device
> > tree, and for each of the ports (A or B).
> >
> > Do so by using the new device-tree property named
> > "modem-control-line-ports" (property added in separate patch).
> 
> That's not the name in the patch.

We added a "nxp," prefix at some point.

Do you want me to send a V9 only with this change?

Hugo.


> > When registering GPIO chip controller, mask-out GPIO pins declared as
> > modem control lines according to this new "modem-control-line-ports"
> > DT property.
> >
> > Boards that need to have GPIOS configured as modem control lines
> > should add that property to their device tree. Here is a list of
> > boards using the sc16is7xx driver in their device tree and that may
> > need to be modified:
> >     arm64/boot/dts/freescale/fsl-ls1012a-frdm.dts
> >     mips/boot/dts/ingenic/cu1830-neo.dts
> >     mips/boot/dts/ingenic/cu1000-neo.dts
> 
> Then again, if no one cares about those boards needing a change then
> it can be okay.
> 
> 
> Rob
> 


-- 
Hugo Villeneuve <hugo@...ovil.com>