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From: Lukas Wunner <lukas@wunner.de>
To: Vicente Bergas <vicencb@gmail.com>
Cc: ilpo.jarvinen@linux.intel.com, andriy.shevchenko@linux.intel.com,
	giulio.benetti@micronovasrl.com, gregkh@linuxfoundation.org,
	heikki.krogerus@linux.intel.com, heiko@sntech.de,
	jirislaby@kernel.org, johan@kernel.org,
	linux-api@vger.kernel.org, linux-serial@vger.kernel.org,
	u.kleine-koenig@pengutronix.de
Subject: Re: [PATCH v3 00/12] Add RS485 support to DW UART
Date: Thu, 21 Apr 2022 21:38:51 +0200	[thread overview]
Message-ID: <20220421193851.GA12186@wunner.de> (raw)
In-Reply-To: <20220421153626.120494-1-vicencb@gmail.com>

On Thu, Apr 21, 2022 at 05:36:26PM +0200, Vicente Bergas wrote:
> 2.- Although "linux,rs485-enabled-at-boot-time" is set in the DTS,
> the RTS/DriverEnable line is asserted all the time the /dev/ttyS1
> device file is closed.
> As soon as the device file is openned, the RTS line is deasserted.
> Then it works as expected: it is asserted only during transmissions.
> When the device file is closed again, the RTS line goes back to the
> asserted level and stays there.
> When the rs485 mode is enabled, it is expected that the RTS line be
> deasserted by default.

That's probably the same issue as reported here:

https://lore.kernel.org/linux-serial/20220329085050.311408-1-matthias.schiffer@ew.tq-group.com/

Basically, some drivers have historically used inverse RTS polarity
and others haven't.  I'm still busy sorting out which drivers use
which.  Sorry, this is quite complex and takes some time.

Have you configured "rs485-rts-active-low" in the device tree?
Which kernel version are you using exactly?

Thanks,

Lukas

  reply	other threads:[~2022-04-21 19:39 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-11  8:33 [PATCH v3 00/12] Add RS485 support to DW UART Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 01/12] serial: Store character timing information to uart_port Ilpo Järvinen
2022-04-11 10:52   ` Andy Shevchenko
2022-04-11 10:56     ` Andy Shevchenko
2022-04-11 11:00       ` Andy Shevchenko
2022-04-11  8:33 ` [PATCH v3 02/12] serial: 8250: Handle UART without interrupt on TEMT Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 03/12] serial: 8250_dwlib: RS485 HW half & full duplex support Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 04/12] serial: 8250_dwlib: Implement SW half " Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 05/12] dt_bindings: rs485: Add receiver enable polarity Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 06/12] ACPI / property: Document RS485 _DSD properties Ilpo Järvinen
2022-04-11 11:02   ` Andy Shevchenko
2022-04-11  8:33 ` [PATCH v3 07/12] serial: termbits: ADDRB to indicate 9th bit addressing mode Ilpo Järvinen
2022-04-11  8:33   ` Ilpo Järvinen
2022-04-11  8:33   ` Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 08/12] serial: General support for multipoint addresses Ilpo Järvinen
2022-04-11  8:33   ` Ilpo Järvinen
2022-04-11  8:33   ` Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 09/12] serial: 8250: make saved LSR larger Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 10/12] serial: 8250: create lsr_save_mask Ilpo Järvinen
2022-04-11  8:33 ` [PATCH v3 11/12] serial: 8250_lpss: Use 32-bit reads Ilpo Järvinen
2022-04-11 11:12   ` Andy Shevchenko
2022-04-11  8:33 ` [PATCH v3 12/12] serial: 8250_dwlib: Support for 9th bit multipoint addressing Ilpo Järvinen
2022-04-11 11:19   ` Andy Shevchenko
2022-04-21 15:36 ` [PATCH v3 00/12] Add RS485 support to DW UART Vicente Bergas
2022-04-21 19:38   ` Lukas Wunner [this message]
2022-04-21 20:41     ` Vicente Bergas
2022-04-22  9:25   ` Ilpo Järvinen
2022-04-22 13:07     ` Ilpo Järvinen
2022-04-23 23:57       ` Vicente Bergas
2022-04-25 11:16         ` Ilpo Järvinen

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