Re: [PATCH] Input: tsc200x: Drop hard-coded IRQ edge

From: Linus Walleij <linus.walleij@linaro.org>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: "Linux Input" <linux-input@vger.kernel.org>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Benoît Cousson" <bcousson@baylibre.com>,
	"Tony Lindgren" <tony@atomide.com>
Subject: Re: [PATCH] Input: tsc200x: Drop hard-coded IRQ edge
Date: Mon, 10 May 2021 11:29:08 +0200	[thread overview]
Message-ID: <CACRpkdbXuZOrKyDeBttkMzGvHJbnqVgAnQv=Z=Ui0fHQOOaUMg@mail.gmail.com> (raw)
In-Reply-To: <YJh8s5rU2VE+DyQz@google.com>

On Mon, May 10, 2021 at 2:22 AM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
> On Mon, May 10, 2021 at 01:38:30AM +0200, Linus Walleij wrote:

> > This edge setting should come from the device tree not
> > the driver. Also, most device trees sets this to the
> > falling edge, which is contradictory to what is hardcoded.
>
> I see there are 2 possibilities:
>
> 1. The driver has never worked
> 2. DT interrupt annotation is wrong.
>
> It would be nice to know if we are dealing with 1 or 2, as in case of #2
> we need to adjust DTSes before this patch can be applied.

I looked closer and unfortunately the mess and confusion
is bizarre.

The DTS files we know of are:
arch/arm/boot/dts/am3517-som.dtsi - rising
arch/arm/boot/dts/imx28-tx28.dts - falling
arch/arm/boot/dts/imx35-eukrea-cpuimx35.dtsi - low
arch/arm/boot/dts/imx51-eukrea-cpuimx51.dtsi - low
arch/arm/boot/dts/imx53-tx53-x03x.dts - falling
arch/arm/boot/dts/imx6q-dhcom-som.dtsi - falling
arch/arm/boot/dts/imx6qdl-tx6.dtsi - none
arch/arm/boot/dts/imx6ul-tx6ul.dtsi - none
arch/arm/boot/dts/imx7d-nitrogen7.dts - falling
arch/arm/boot/dts/logicpd-som-lv.dtsi - rising
arch/arm/boot/dts/logicpd-torpedo-baseboard.dtsi - rising
arch/arm/boot/dts/omap3-gta04.dtsi - falling
arch/arm/boot/dts/omap3-n900.dts - rising
arch/arm/boot/dts/omap4-var-som-om44.dtsi - low
arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi - falling

We can assume that some of this is the result of board
engineers introducing inverters on the board as is custom,
so the flags are actually correct when set to falling, just
that we don't model the inverter.

In the case of imx6qdl-tx6 and imx6ul-tx6ul with "none" IRQ
type I assume this flag in the driver is actually necessary
for the device to work at all.

In the cases where rising is set, the addition of the flag is
plain tautology, just setting what is already set.

In the cases where falling are set the interrupts will arrive
on both edges (if the hardware can provide that, which is
not always the case) and as a result fire twice as many
interrupts as they should, probably with zero effect on the
second IRQ, just reporting nothing.

The combination with active low is weird. I wonder what
happens there.

I am just confused now and have no idea what to do about
it...

But I just CC all the Freescale and OMAP people who
seem to maintain these DTS files so they can clarify
how well assigned these edges, none and active low (!)
IRQs are.

Yours,
Linus Walleij