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Message-ID: <47B3EE27.6000902@gandalf.sssup.it>
Date: Thu, 14 Feb 2008 08:30:47 +0100
From: michael <trimarchi@...dalf.sssup.it>
To: Remy Bohmer <linux@...mer.net>
CC: Haavard Skinnemoen <hskinnemoen@...el.com>, fabio@...dalf.sssup.it,
Andrew Victor <linux@...im.org.za>,
Chip Coldwell <coldwell@...hat.com>,
Marc Pignat <marc.pignat@...s.ch>,
David Brownell <david-b@...bell.net>,
linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler
Hi,
Remy Bohmer wrote:
> Hello All,
>
>
>> All works now for me with preempt-rt. The problem is using hrtimer.
>> I think that hrtimer are executed with interrupts disabled so, if
>> this happen when I must receive a char, i have an overrun.
>>
>
> No, they share the same interrupt line...
>
I think that the hrtimer use and other interrupt line. The
AT91SAM9260_ID_TC2.
> So, while the timer interrupt handler is running, the serial handler
> has to wait until the timer interrupt handler has finished.
> Notice that the HRT interrupt handler is quite heavy and takes a long
> time to complete.
>
The problem is the heavy of HRT interrupt handler of course.
> And, as I already mentioned, related to the 1 byte FIFO and a
> interrupt latency of about 85us (without HRT), it is logical that you
> can get an overrun at the higher serial speeds... (>=115200bps)
>
>
I don't have the same problem without the hrtimer, I suppose the the
timer latency
is not so heavy.
>> The only solution was the dma support to serial device.
>>
>
> Or, use flow control?
>
>
>
Yes :)
Michael
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