From: Eugeniu Rosca <erosca@de.adit-jv.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Eugeniu Rosca <erosca@de.adit-jv.com>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Jonathan Corbet <corbet@lwn.net>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Harish Jenny K N <harish_kandiga@mentor.com>,
Alexander Graf <graf@amazon.com>,
Peter Maydell <peter.maydell@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Phil Reid <preid@electromag.com.au>,
Marc Zyngier <marc.zyngier@arm.com>,
Christoffer Dall <christoffer.dall@arm.com>,
Magnus Damm <magnus.damm@gmail.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
QEMU Developers <qemu-devel@nongnu.org>,
Eugeniu Rosca <roscaeugeniu@gmail.com>
Subject: Re: [PATCH v3 0/7] gpio: Add GPIO Aggregator/Repeater
Date: Mon, 20 Jan 2020 13:14:39 +0100 [thread overview]
Message-ID: <20200120121439.GA24951@lxhi-065.adit-jv.com> (raw)
In-Reply-To: <CAMuHMdUUc17n0TxOrtQNby+ZiHDpz-aEh-ncnkz50vcwQe6z6w@mail.gmail.com>
Hi Geert,
On Mon, Jan 20, 2020 at 10:33:53AM +0100, Geert Uytterhoeven wrote:
> On Sat, Jan 18, 2020 at 2:46 AM Eugeniu Rosca <erosca@de.adit-jv.com> wrote:
> > The only unexpected thing is seeing below messages (where gpiochip99 and
> > gpiochip22 are inexisting gpiochip names, mistakenly provided on command
> > line prior to passing the correct name):
> >
> > root@rcar-gen3:~# echo gpiochip6 12-13 > /sys/bus/platform/drivers/gpio-aggregator/new_device
> > [ 915.572905] gpio-aggregator gpio-aggregator.0: cannot find GPIO chip gpiochip99, deferring
> > [ 915.584224] gpio-aggregator gpio-aggregator.2: cannot find GPIO chip gpiochip99, deferring
> > [ 915.865281] gpio-aggregator gpio-aggregator.29: cannot find GPIO chip gpiochip22, deferring
> >
> > Obviously, in the above case, due to a typo in the names, the gpio
> > chips will never be found, no matter how long gpio-aggregator defers
>
> Indeed, that is expected behavior: you have created platform devices
> referring to resources that are not available.
Got it. Sounds reasonable to me.
>
> > their probing. Unfortunately, the driver will continuously emit those
> > messages, upon each successfully created/aggregated gpiochip. I built
>
> That is expected behavior, too: every time the driver core manages to
> bind a device to a driver, it will retry all previously deferred probes,
> in the hope they can be satisfied by the just bound device.
>
> Note that you can destroy these bogus devices, using e.g.
>
> # echo gpio-aggregator.0 > \
> /sys/bus/platform/drivers/gpio-aggregator/delete_device
Yep, I can get rid of the bogus devices this way. Thanks!
>
> > gpio-aggregator as a loadable module, if that's relevant.
>
> Modular or non-modular shouldn't matter w.r.t. this behavior.
> Although unloading the module should get rid of the cruft.
Yes, indeed!
>
> > Another comment is that, while the series _does_ allow specifying
> > gpio lines in the DTS (this would require a common compatible string
> > in gpio_aggregator_dt_ids[] and in the DTS node) and while those lines
> > are indeed exposed to userspace, based on my testing, these same gpio
> > lines are marked as "used/reserved" by the kernel. This means that
> > operating on those gpio pins from userspace will not be possible.
> > For instance, gpioget/gpioset return "Device or resource busy":
> >
> > gpioget: error reading GPIO values: Device or resource busy
> > gpioset: error setting the GPIO line values: Device or resource busy
> >
> > I guess Harish will be unhappy about that, as his expectation was that
> > upon merging gpio-aggregator with gpio-inverter, he will be able to
> > describe GPIO polarity and names in DTS without "hogging" the pins.
> > Perhaps this can be supplemented via an add-on patch later on?
>
> When aggregating GPIO lines, the original GPIO lines are indeed marked
> used/reserved, so you cannot use them from userspace.
> However, you are expected to use them through the newly created virtual
> gpiochip representing the aggregated GPIO lines.
>
> You can try this using the "door" example in
> Documentation/admin-guide/gpio/gpio-aggregator.rst, after replacing
> gpio2 {19,20} by gpio6 {12,13} to suit your H3ULCB.
Confirmed. The example works like a charm. One difference between
the runtime-created and DTS-created gpiochips is the name:
- gpio-aggregator.<number>, for the ones created via sysfs
- <name-of-DTS-node>, for the ones created via DTS
Seeing this behavior on my target, I believe the expectations of
Harish should be met w/o any major limitations.
>
> > For the whole series (leaving the above findings to your discretion):
> >
> > Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
> > Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
The recent [v3] discussion actually applies to [v4], for which I did
review and testing. Will relay the signatures to the latest version.
Thank you very much.
--
Best Regards,
Eugeniu
prev parent reply other threads:[~2020-01-20 12:14 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 8:42 [PATCH v3 0/7] gpio: Add GPIO Aggregator/Repeater Geert Uytterhoeven
2019-11-27 8:42 ` [PATCH v3 1/7] gpiolib: Add GPIOCHIP_NAME definition Geert Uytterhoeven
2019-11-28 3:38 ` Ulrich Hecht
2019-12-02 21:17 ` Eugeniu Rosca
2019-12-12 10:37 ` Linus Walleij
2019-11-27 8:42 ` [PATCH v3 2/7] gpiolib: Add support for gpiochipN-based table lookup Geert Uytterhoeven
2019-11-28 3:38 ` Ulrich Hecht
2019-12-12 13:20 ` Linus Walleij
2019-12-12 13:33 ` Geert Uytterhoeven
2019-12-12 14:36 ` Linus Walleij
2019-11-27 8:42 ` [PATCH v3 3/7] gpiolib: Add support for GPIO line " Geert Uytterhoeven
2019-11-28 3:39 ` Ulrich Hecht
2019-12-12 13:40 ` Linus Walleij
2019-11-27 8:42 ` [PATCH v3 4/7] dt-bindings: gpio: Add gpio-repeater bindings Geert Uytterhoeven
2019-11-28 3:39 ` Ulrich Hecht
2019-12-03 5:51 ` Harish Jenny K N
2019-12-05 21:06 ` Rob Herring
2019-12-06 9:17 ` Geert Uytterhoeven
2019-12-06 15:03 ` Rob Herring
2020-01-06 8:12 ` Geert Uytterhoeven
2020-01-07 9:22 ` Harish Jenny K N
2020-01-16 5:09 ` Harish Jenny K N
2019-11-27 8:42 ` [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver Geert Uytterhoeven
2019-11-27 14:15 ` Eugeniu Rosca
2019-11-27 14:33 ` Geert Uytterhoeven
2019-11-28 3:40 ` Ulrich Hecht
2019-12-03 5:42 ` Harish Jenny K N
2019-12-03 8:17 ` Geert Uytterhoeven
2019-12-03 8:51 ` Harish Jenny K N
2019-12-03 10:51 ` Eugeniu Rosca
2020-01-09 13:35 ` Geert Uytterhoeven
2020-01-09 13:49 ` Eugeniu Rosca
2019-12-12 14:34 ` Linus Walleij
2019-12-12 15:24 ` Geert Uytterhoeven
2020-01-04 0:38 ` Linus Walleij
2020-01-06 8:23 ` Geert Uytterhoeven
2020-01-08 23:12 ` Linus Walleij
2019-11-27 8:42 ` [PATCH v3 6/7] docs: gpio: Add GPIO Aggregator/Repeater documentation Geert Uytterhoeven
2019-11-28 3:41 ` Ulrich Hecht
2019-12-12 14:42 ` Linus Walleij
2019-12-12 14:48 ` Geert Uytterhoeven
2020-01-04 0:21 ` Linus Walleij
2020-01-06 8:06 ` Geert Uytterhoeven
2019-11-27 8:42 ` [PATCH v3 7/7] MAINTAINERS: Add GPIO Aggregator/Repeater section Geert Uytterhoeven
2019-12-03 5:38 ` Harish Jenny K N
2020-01-18 1:46 ` [PATCH v3 0/7] gpio: Add GPIO Aggregator/Repeater Eugeniu Rosca
2020-01-20 9:33 ` Geert Uytterhoeven
2020-01-20 12:14 ` Eugeniu Rosca [this message]
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