linux-kernel - Re: [PATCH] atmel_serial: Fix break handling

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Message-ID: <20070605140720.4bdf887a@newbox>
Date:	Tue, 5 Jun 2007 14:07:20 +0300
From:	Ivan Kuten <ivan.kuten@...mwad.com>
To:	Haavard Skinnemoen <hskinnemoen@...el.com>
Cc:	Andrew Victor <andrew@...people.com>,
	Russell King <rmk@....linux.org.uk>,
	Nicolas Ferre <nicolas.ferre@....atmel.com>,
	Patrice Vilchez <patrice.vilchez@....atmel.com>,
	linux-kernel@...r.kernel.org,
	Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: Re: [PATCH] atmel_serial: Fix break handling

On Thu, 31 May 2007 21:31:31 +0200
Haavard Skinnemoen wrote:

> It's been almost a year since the last patch I sent attempting to fix
> this. Sorry for not following up any sooner.
> 
> Anyway, here's a new attempt. It should work even if we miss some
> interrupts, and it should not break break handling by ignoring the
> return value from uart_handle_break() as Russell pointed out.
> 
> There may be cases which aren't handled well: If you send two breaks
> with no characters in between and we miss an interrupt on the first
> one, the driver probably gets a bit confused. I don't see any way to
> fix this, but the driver should get un-confused upon reception of the
> next character.
> 
> I've tested this with Magic SysRq on ATSTK1000: It works with this
> patch but not without. Ivan Kuten reported in a different thread that
> SysRq didn't work on AT91RM9200 and I very much doubt it works on
> AT91SAM926x.
> 
> The break count in /proc/tty/driver/atmel_serial also makes more sense
> with this patch applied; without it, the break count increments by two
> every time I send a break.
> 
>  drivers/serial/atmel_serial.c |   32 ++++++++++++++++++++++++++++++--
>  1 files changed, 30 insertions(+), 2 deletions(-)
> 

Hi Haavard, 

I tried to test your patch on AT91RM9200 with Magic SysRq sequence, unfortunately without 
success - SysRq still does not work. You mention "break count increments" where do you check it ? I have 
cat /proc/tty/driver/atmel_serial 
serinfo:1.0 driver revision:
0: uart:ATMEL_SERIAL mmio:0xFEFFF200 irq:1 tx:8554 rx:623 fe:25 RTS|CTS|DTR|DSR|CD|RI
1: uart:ATMEL_SERIAL mmio:0xFFFC0000 irq:6 tx:0 rx:0 CTS|DSR|CD|RI
2: uart:ATMEL_SERIAL mmio:0xFFFC4000 irq:7 tx:0 rx:0 RI
3: uart:ATMEL_SERIAL mmio:0xFFFC8000 irq:8 tx:0 rx:0 DSR|CD|RI
4: uart:ATMEL_SERIAL mmio:0xFFFCC000 irq:9 tx:0 rx:0 CTS|DSR|CD|RI

no any break counter.

BR,
Ivan



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