From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Sander Vanheule <sander@svanheule.net>
Cc: 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>,
Michael Walle <michael@walle.cc>,
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>,
Andrew Lunn <andrew@lunn.ch>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 2/8] gpio: regmap: Add quirk for aliased data registers
Date: Sun, 13 Jun 2021 00:29:49 +0300 [thread overview]
Message-ID: <CAHp75VeOMb2xUJ+g2UQJnBybmehmYr0dGPEzDZObUGr=Q95+wA@mail.gmail.com> (raw)
In-Reply-To: <5d8e5e8a29ecf39da48beb94c42003a5c686ec4e.1623532208.git.sander@svanheule.net>
On Sun, Jun 13, 2021 at 12:13 AM Sander Vanheule <sander@svanheule.net> wrote:
>
> Some chips have the read-only input and write-only output data registers
> aliased to the same offset. As a result it is not possible to perform
> read-modify-writes on the output values, when a line is still configured
> as input.
>
> Add a quirk for aliased data registers, and document how the regmap
> should be set up for correct operation.
I still believe that there is no issue with gpio-regmap and we don't
need any quirk there.
The issue is in the regmap APIs (implementation) itself. Hardware with
the concept of reading X / writing Y at the same offset is okay per
se. regmaps doesn't support it properly and should be fixed (amended)
in a way that you provide this kind of register description thru
regmap configuration or so.
I expressed the idea of trying to implement regmap-8250 as an example
of the support for such hardware. And OTOH that this kind of hardware
is not unusual.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-06-12 21:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 21:12 [PATCH v5 0/8] RTL8231 GPIO expander support Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 1/8] regmap: Support atomic forced uncached reads Sander Vanheule
2021-06-12 21:23 ` Andy Shevchenko
2021-06-14 10:33 ` Mark Brown
2021-06-12 21:12 ` [PATCH v5 2/8] gpio: regmap: Add quirk for aliased data registers Sander Vanheule
2021-06-12 21:29 ` Andy Shevchenko [this message]
2021-07-07 20:53 ` Sander Vanheule
2021-07-08 14:23 ` Mark Brown
2021-06-12 21:12 ` [PATCH v5 3/8] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 4/8] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 5/8] mfd: Add RTL8231 core device Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 6/8] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 7/8] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 8/8] MAINTAINERS: Add RTL8231 MFD driver Sander Vanheule
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