From: peter@hurleysoftware•com (Peter Hurley)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/5] doc: DT: Add Generic Serial Device Tree Bindings
Date: Mon, 18 Apr 2016 10:02:55 -0700 [thread overview]
Message-ID: <5715133F.2040103@hurleysoftware.com> (raw)
In-Reply-To: <CACQ1gAhnEuCZbzpyiAcCx_kRhzCBvWAVVaecUdUhvu4vDD0REw@mail.gmail.com>
On 04/18/2016 08:43 AM, Richard Genoud wrote:
> 2016-04-18 14:34 GMT+02:00 Geert Uytterhoeven <geert@linux-m68k•org>:
>> Hi Arnd,
>>
>> CC Richard (serial-mctrl-gpio)
>> CC Grant (ePAPR successor) and Frank
>>
>> On Sat, Apr 16, 2016 at 6:30 PM, Arnd Bergmann <arnd@arndb•de> wrote:
>>> On Thursday 14 April 2016 14:13:19 Geert Uytterhoeven wrote:
[...]
>>>> - out1-gpios: Must contain a GPIO specifier, referring to the GPIO pin to be
>>>> used as the UART's OUT1 line.
>>>> - out2-gpios: Must contain a GPIO specifier, referring to the GPIO pin to be
>>>> used as the UART's OUT2 line.
>>>
>>> I had to look up what OUT1 and OUT2 are, but I still don't see how you'd
>>> implement them using a GPIO line: From all I can tell, these are usually
>>> internal registers in a hardware uart but they are not assigned to an
>>> external line on the standard db9 or even the old db25 connectors. Should
>>> we drop these instead?
Yeah, not sure how those snuck in for gpios.
The original 8250/16550 uarts had OUT1 and OUT2 pins, and OUT1 could be used
like gpio. That was 3 decades ago though so maybe we don't need to try to
recreate that tech again :)
>> They're indeed fairly exotic, and they're burried deeply in the ns16550
>> datasheet. We do have TIOCM_OUT1 and TIOCM_LOOP in asm-generic/termios.h,
>> probably for obscure historical reasons.
Please leave the bit defs alone.
>> If we drop them, I guess they should be removed from the helper code in
>> drivers/tty/serial/serial_mctrl_gpio.c, too? There don't seem to be any
>> current users.
> I must confess that I don't really know what TIOCM_OUT1&2 are for.
> (I implemented them for completeness)
> But it seems that OUT2 is used in some drivers:
> drivers/tty/serial/omap-serial.c:
> /*
> * Most PC uarts need OUT2 raised to enable interrupts.
> */
> up->port.mctrl |= TIOCM_OUT2;
There's no need for OUT1 and OUT2 gpios; let's fix that.
Regards,
Peter Hurley
next prev parent reply other threads:[~2016-04-18 17:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 12:13 [PATCH 0/5] serial: Add Generic Serial Device Tree Bindings Geert Uytterhoeven
2016-04-14 12:13 ` [PATCH 1/5] doc: DT: " Geert Uytterhoeven
2016-04-14 17:21 ` Rob Herring
2016-04-16 16:30 ` Arnd Bergmann
2016-04-18 12:34 ` Geert Uytterhoeven
2016-04-18 14:05 ` Arnd Bergmann
2016-04-18 15:43 ` Richard Genoud
2016-04-18 17:02 ` Peter Hurley [this message]
2016-04-14 12:13 ` [PATCH 2/5] serial: imx: Use generic uart-has-rtscts DT property Geert Uytterhoeven
2016-04-14 17:22 ` Rob Herring
2016-04-14 17:38 ` Geert Uytterhoeven
2016-04-14 12:13 ` [PATCH 3/5] serial: mxs-auart: " Geert Uytterhoeven
2016-04-14 12:13 ` [PATCH 4/5] serial: sirf: Introduce helper variable struct device_node *np Geert Uytterhoeven
2016-04-14 12:13 ` [PATCH 5/5] serial: sirf: Use generic uart-has-rtscts DT property Geert Uytterhoeven
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5715133F.2040103@hurleysoftware.com \
--to=peter@hurleysoftware$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox