From: Lukas Wunner <lukas@wunner.de>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Jiri Slaby" <jirislaby@kernel.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
"Conor Dooley" <conor+dt@kernel.org>,
devicetree@vger.kernel.org,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
"Crescent CY Hsieh" <crescentcy.hsieh@moxa.com>,
"Lino Sanfilippo" <LinoSanfilippo@gmx.de>,
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Subject: Re: [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios binding
Date: Thu, 23 Nov 2023 11:38:02 +0100 [thread overview]
Message-ID: <20231123103802.GA30056@wunner.de> (raw)
In-Reply-To: <e731c0a9-7a5c-41c3-87aa-d6937b99d01a@rasmusvillemoes.dk>
On Thu, Nov 23, 2023 at 11:07:16AM +0100, Rasmus Villemoes wrote:
> On 22/11/2023 15.53, Lukas Wunner wrote:
> > But if that patch gets accepted, we'd have *three* different modes:
> > RS-232, RS-485, RS-422. A single GPIO seems insufficient to handle that.
> > You'd need at least two GPIOs.
>
> I don't see Crescent introducing any new gpio that needs to be handled.
> In fact, I can't even see why from the perspective of the software that
> rs422 isn't just rs232; there's no transmit enable pin that needs to be
> handled. But maybe the uart driver does something different in rs422
> mode; I assume he must have some update of some driver, since otherwise
> the new rs422 bit should be rejected by the core. So I can't really see
> the whole picture of that rs422 story.
The question is, could we conceivably have the need to support
switching between the three modes RS-232, RS-485, RS-422.
If yes, then the GPIO mux interface should probably allow for that.
As a case in point, the Siemens IOT 2040 has two serial ports
which can be set to either of those three modes. The signals
are routed to the same D-sub socket, but the pins used are
different. See page 46 and 47 of this document:
https://cache.industry.siemens.com/dl/files/658/109741658/att_899623/v1/iot2000_operating_instructions_enUS_en-US.pdf
The driver for this product is 8250_exar.c. It's an Intel-based
product, so no devicetree, but it shows that such use cases exist.
Thanks,
Lukas
next prev parent reply other threads:[~2023-11-23 10:38 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-20 15:10 [PATCH 0/2] serial: add rs485-mux-gpio dt binding and support Rasmus Villemoes
2023-11-20 15:10 ` [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios binding Rasmus Villemoes
2023-11-21 7:52 ` Krzysztof Kozlowski
2023-11-21 8:27 ` Rasmus Villemoes
2023-11-21 8:34 ` Krzysztof Kozlowski
2023-11-21 9:28 ` Rasmus Villemoes
2023-11-22 18:00 ` Krzysztof Kozlowski
2023-11-22 14:53 ` Lukas Wunner
2023-11-23 10:07 ` Rasmus Villemoes
2023-11-23 10:38 ` Lukas Wunner [this message]
2023-11-23 13:48 ` Rasmus Villemoes
2023-11-25 23:40 ` Lino Sanfilippo
2023-11-27 12:14 ` Christoph Niedermaier
2023-12-06 15:42 ` Lino Sanfilippo
2023-12-07 12:35 ` Andy Shevchenko
2023-12-09 11:24 ` Lino Sanfilippo
2023-12-09 11:47 ` Lino Sanfilippo
2023-12-11 13:07 ` Andy Shevchenko
2023-12-14 8:52 ` Lino Sanfilippo
2023-12-14 10:24 ` Crescent CY Hsieh
2023-12-14 13:41 ` Christoph Niedermaier
2023-12-14 14:04 ` Lino Sanfilippo
2023-12-14 14:50 ` Christoph Niedermaier
2023-12-15 22:13 ` Lino Sanfilippo
2023-12-18 9:08 ` Christoph Niedermaier
2023-12-21 15:53 ` Lukas Wunner
2023-12-23 12:49 ` Christoph Niedermaier
2023-12-23 13:40 ` Lino Sanfilippo
2023-12-24 10:11 ` Christoph Niedermaier
2023-12-28 23:25 ` Lukas Wunner
2023-11-20 15:10 ` [PATCH 2/2] serial: core: implement support for rs485-mux-gpios Rasmus Villemoes
2023-11-20 23:28 ` Lino Sanfilippo
2023-11-21 10:49 ` Dan Carpenter
2023-11-22 15:10 ` Lukas Wunner
2023-12-04 5:00 ` Dan Carpenter
2023-11-22 14:57 ` [PATCH 0/2] serial: add rs485-mux-gpio dt binding and support Andy Shevchenko
-- strict thread matches above, loose matches on Subject: below --
2023-12-27 17:40 [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios binding Andy Shevchenko
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