linux-kernel - Re: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround for AM33xx

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Message-ID: <20140929161505.GF13142@linutronix.de>
Date:	Mon, 29 Sep 2014 18:15:05 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	tony@...mide.com, balbi@...com, gregkh@...uxfoundation.org,
	Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround
 for AM33xx

* Peter Hurley | 2014-09-17 08:20:41 [-0400]:

>> So I connected my am335x-evm
>> with beagle board xm because both of them have an old fashion UART
>> connector (instead those uart-to-usb). Both configured with HW-Flow and
>> I haven't seen the function invoked but I saw "port->icount.overrun"
>> being incremented. This shouldn't happen. So I am a little puzzled here…
>
>Yeah, that's weird. Do you have a break-out box to confirm that RTS/CTS are
>being driven?

=>
- beagle board
  According to schematics the board has only RX and TX connected. No
  RTS/CTS

- am335x-evm
  The schematics say "DNI" next to a resistor on RTS/CTS. DNI stands
  most likely for "Do Not Install". With a scope it looks like the the
  wire behind the MAX is open.

- beagle bone black
  Only RX and TX are wired towards the USB2serial device.

In short: each device I have has RTS/CTS not working/connected and I
can't test HW handshake with HW available.

>Regards,
>Peter Hurley

Sebastian
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