From: Michael Walle <michael@walle.cc>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>,
Sander Vanheule <sander@svanheule.net>,
Andrew Lunn <andrew@lunn.ch>, Pavel Machek <pavel@ucw.cz>,
Rob Herring <robh+dt@kernel.org>,
Lee Jones <lee.jones@linaro.org>, Mark Brown <broonie@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Linux LED Subsystem <linux-leds@vger.kernel.org>,
devicetree <devicetree@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 0/6] RTL8231 GPIO expander support
Date: Sun, 30 May 2021 23:22:21 +0200 [thread overview]
Message-ID: <c7239e0cbbc9748925410937a914bd8a@walle.cc> (raw)
In-Reply-To: <CAHp75VcFmU4rJ6jL204xGFM=s2LV=KQmsV8E75BpuSAZMXBn0w@mail.gmail.com>
Am 2021-05-30 20:16, schrieb Andy Shevchenko:
> On Sun, May 30, 2021 at 7:51 PM Hans de Goede <hdegoede@redhat.com>
> wrote:
>> On 5/30/21 6:19 PM, Sander Vanheule wrote:
>> > On Fri, 2021-05-28 at 08:37 +0200, Michael Walle wrote:
>
> ...
>
>> > I think I found a solution!
nice!
>> > As Michael suggested, I tried raw register reads and writes, to eliminate any
>> > side effects of the intermediate code. I didn't use the ioctls (this isn't a
>> > netdev), but I found regmap's debugfs write functionality, which allowed me to
>> > do the same.
>> >
>> > I was trying to reproduce the behaviour I reported earlier, but couldn't. The
>> > output levels were always the intended ones. At some point I realised that the
>> > regmap_update_bits function does a read-modify-write, which might shadow the
>> > actual current output value.
>> > For example:
>> > * Set output low: current out is low
>> > * Change to input with pull-up: current out is still low, but DATAx reads high
>> > * Set output high: RMW reads a high value (the input), so assumes a write is
>> > not necessary, leaving the old output value (low).
>> >
>> > Currently, I see two options:
>> > * Use regmap_update_bits_base to avoid the lazy RMW behaviour
>> > * Add a cache for the output data values to the driver, and only use these
>> > values to write to the output registers. This would allow keeping lazy RMW
>> > behaviour, which may be a benefit on slow busses.
>> >
>> > With either of these implemented, if I set the output value before the
>> > direction, everything works! :-)
>> >
>> > Would you like this to be added to regmap-gpio, or should I revert back to a
>> > device-specific implementation?
>>
>> Regmap allows you to mark certain ranges as volatile, so that they
>> will not
>> be cached, these GPIO registers containing the current pin value seems
>> like
>> a good candidate for this. This is also necessary to make reading the
>> GPIO
>> work without getting back a stale, cached value.
>
> After all it seems a simple missed proper register configuration in
> the driver for regmap.
> Oh, as usual something easy-to-solve requires tons of time to find it.
> :-)
>
> Sander, I think you may look at gpio-pca953x.c to understand how it
> works (volatility of registers).
But as far as I see is the regmap instantiated without a cache?
-michael
next prev parent reply other threads:[~2021-05-30 21:22 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 12:25 [PATCH 0/5] RTL8231 GPIO expander support Sander Vanheule
2021-05-11 12:25 ` [PATCH 1/5] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-05-17 22:31 ` Rob Herring
2021-05-19 16:39 ` Sander Vanheule
2021-05-11 12:25 ` [PATCH 2/5] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-05-17 22:38 ` Rob Herring
2021-05-19 16:53 ` Sander Vanheule
2021-05-11 12:25 ` [PATCH 3/5] mfd: Add RTL8231 core device Sander Vanheule
2021-05-12 12:29 ` kernel test robot
2021-05-12 13:13 ` kernel test robot
2021-05-19 14:58 ` Lee Jones
2021-05-19 15:11 ` Sander Vanheule
2021-05-11 12:25 ` [PATCH 4/5] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-05-11 12:25 ` [PATCH 5/5] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
[not found] ` <CAHp75VffoKyyPJbdtKMLx575c9LT0S8+EHOk7Mw36j=aTL6Q4Q@mail.gmail.com>
2021-05-16 21:40 ` [PATCH 0/5] RTL8231 GPIO expander support Sander Vanheule
2021-05-17 8:13 ` Andy Shevchenko
2021-05-17 8:50 ` Sander Vanheule
2021-05-17 19:32 ` Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 0/7] " Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 1/7] regmap: Add MDIO bus support Sander Vanheule
2021-05-19 16:12 ` Mark Brown
2021-05-17 19:28 ` [PATCH v2 2/7] gpio: regmap: Add configurable dir/value order Sander Vanheule
2021-05-17 21:06 ` Andy Shevchenko
2021-05-18 1:40 ` Andrew Lunn
2021-05-18 11:39 ` Sander Vanheule
2021-05-23 22:21 ` Sander Vanheule
2021-05-18 8:39 ` Michael Walle
2021-05-18 10:39 ` Andy Shevchenko
2021-05-23 21:19 ` Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 3/7] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 4/7] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-05-18 22:02 ` Linus Walleij
2021-05-17 19:28 ` [PATCH v2 5/7] mfd: Add RTL8231 core device Sander Vanheule
2021-05-17 21:18 ` Andy Shevchenko
2021-05-23 21:28 ` Sander Vanheule
2021-05-24 7:49 ` Andy Shevchenko
2021-05-24 7:50 ` Sander Vanheule
2021-05-24 7:55 ` Andy Shevchenko
2021-05-24 8:04 ` Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 6/7] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-05-17 21:42 ` Andy Shevchenko
2021-05-17 21:46 ` Andy Shevchenko
2021-05-23 21:42 ` Sander Vanheule
2021-05-17 19:28 ` [PATCH v2 7/7] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
2021-05-17 22:00 ` Andy Shevchenko
2021-05-23 21:53 ` Sander Vanheule
2021-05-19 16:10 ` (subset) [PATCH v2 0/7] RTL8231 GPIO expander support Mark Brown
2021-05-23 22:33 ` [PATCH v3 0/6] " Sander Vanheule
2021-05-23 22:33 ` [PATCH v3 1/6] gpio: regmap: Add quirk for output data register Sander Vanheule
2021-05-28 6:40 ` Michael Walle
2021-06-03 10:03 ` Sander Vanheule
2021-05-31 7:25 ` Bartosz Golaszewski
2021-05-23 22:34 ` [PATCH v3 2/6] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-06-02 18:58 ` Rob Herring
2021-05-23 22:34 ` [PATCH v3 3/6] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-05-27 23:31 ` Linus Walleij
2021-06-02 19:02 ` Rob Herring
2021-05-23 22:34 ` [PATCH v3 4/6] mfd: Add RTL8231 core device Sander Vanheule
2021-05-24 8:02 ` Andy Shevchenko
2021-05-24 8:23 ` Sander Vanheule
2021-05-24 10:18 ` Andy Shevchenko
2021-05-24 11:41 ` Sander Vanheule
2021-05-23 22:34 ` [PATCH v3 5/6] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-05-28 6:29 ` Michael Walle
2021-05-28 6:42 ` Sander Vanheule
2021-05-28 6:43 ` Michael Walle
2021-05-23 22:34 ` [PATCH v3 6/6] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
2021-05-24 10:24 ` Andy Shevchenko
2021-05-24 12:04 ` Sander Vanheule
2021-05-24 12:47 ` Andy Shevchenko
2021-05-24 15:30 ` Sander Vanheule
2021-05-24 1:10 ` [PATCH v3 0/6] RTL8231 GPIO expander support Andrew Lunn
2021-05-24 7:53 ` Andy Shevchenko
2021-05-24 11:41 ` Sander Vanheule
2021-05-24 12:54 ` Andy Shevchenko
2021-05-24 15:03 ` Sander Vanheule
2021-05-24 16:30 ` Andy Shevchenko
2021-05-25 17:11 ` Andy Shevchenko
2021-05-25 18:00 ` Sander Vanheule
2021-05-26 21:02 ` Sander Vanheule
2021-05-27 10:38 ` Andy Shevchenko
2021-05-27 10:41 ` Hans de Goede
2021-05-24 15:20 ` Sander Vanheule
2021-05-28 6:37 ` Michael Walle
2021-05-30 16:19 ` Sander Vanheule
2021-05-30 16:51 ` Hans de Goede
2021-05-30 18:16 ` Andy Shevchenko
2021-05-30 21:22 ` Michael Walle [this message]
2021-05-31 8:36 ` Sander Vanheule
2021-05-31 10:02 ` Michael Walle
[not found] ` <CAHp75VfOrUBRQH1vrXEwHN4ZPojQfQju-_wp_3djZeozEaatug@mail.gmail.com>
2021-05-31 15:33 ` [PATCH 0/5] " Sander Vanheule
2021-05-31 15:48 ` Andy Shevchenko
2021-06-01 11:49 ` Michael Walle
2021-06-01 15:24 ` Andy Shevchenko
2021-06-02 20:20 ` Sander Vanheule
2021-06-01 9:59 ` [PATCH v3 0/6] " Linus Walleij
2021-06-01 10:18 ` Michael Walle
2021-06-01 10:51 ` Linus Walleij
2021-06-01 11:41 ` Michael Walle
2021-06-01 11:48 ` Linus Walleij
2021-06-03 10:00 ` [PATCH v4 0/5] " Sander Vanheule
2021-06-03 10:00 ` [PATCH v4 1/5] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-06-03 10:00 ` [PATCH v4 2/5] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-06-03 10:00 ` [PATCH v4 3/5] mfd: Add RTL8231 core device Sander Vanheule
2021-06-03 10:58 ` Andy Shevchenko
2021-06-03 11:28 ` Sander Vanheule
2021-06-03 14:03 ` Andrew Lunn
2021-06-03 15:20 ` Sander Vanheule
2021-06-05 11:07 ` Sander Vanheule
2021-06-03 10:00 ` [PATCH v4 4/5] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-06-03 10:18 ` Andy Shevchenko
2021-06-04 22:10 ` Linus Walleij
2021-06-03 10:00 ` [PATCH v4 5/5] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
2021-06-03 11:01 ` Andy Shevchenko
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