From: Mark Jackson <mpfj-list@newflow.co.uk>
To: balbi@ti.com
Cc: Linux OMAP Mailing List <linux-omap@vger.kernel.org>
Subject: Re: rts-gpio DT binding
Date: Tue, 18 Mar 2014 17:04:47 +0000 [thread overview]
Message-ID: <53287CAF.9040708@newflow.co.uk> (raw)
In-Reply-To: <20140318165536.GH14373@saruman.home>
On 18/03/14 16:55, Felipe Balbi wrote:
> Hi Mark,
>
> I'm looking at the omap-serial driver and saw that you added rts-gpio
> binding in commit 4a0ac0f55b18dc297a87a85417fcf068658bf103 (OMAP: add
> RS485 support) but, as it turns out, gpio0_13 and gpio2_15 are both
> actual RTS signals.
>
> Instead of adding that extra GPIO handling, why didn't you just mux
> those signals as RTS and enable auto-RTS/auto-CTS feature ?
>
> It looks to me like that's highly unnecessary binding.
I agree !!
I think it was to allow delays pre- and post- sending the comms data.
Several RS485 drivers require a "warm up" time before they will
transmit data correctly, and also need a "cool down" time to prevent
clipping of the last few bits of data.
IIRC the built-in RTS handling did not allow for this.
It also allows the RTS signal to be "inverted", again required for
some RS485 driver chips.
However, I'll dig into why I did this and report back.
Mark J.
next prev parent reply other threads:[~2014-03-18 17:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-18 16:55 rts-gpio DT binding Felipe Balbi
2014-03-18 17:04 ` Mark Jackson [this message]
2014-03-18 17:11 ` Felipe Balbi
2014-03-18 17:18 ` Felipe Balbi
2014-03-18 17:22 ` Felipe Balbi
2014-03-19 9:15 ` Mark Jackson
2014-03-19 14:59 ` Felipe Balbi
2014-03-19 17:02 ` Mark Jackson
2014-03-19 19:04 ` Felipe Balbi
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