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Subject: Re: omap uart + dma issues (Re: [PATCH] tty: serial: 8250_omap: do
 not defer termios changes)
To: Peter Hurley <peter@hurleysoftware.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        John Ogness <john.ogness@linutronix.de>,
        Tony Lindgren <tony@atomide.com>
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 <570D8C16.1010702@hurleysoftware.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        <linux-kernel@vger.kernel.org>, <linux-serial@vger.kernel.org>,
        <linux-omap@vger.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
From: Sekhar Nori <nsekhar@ti.com>
Message-ID: <570E295B.2030708@ti.com>
Date: Wed, 13 Apr 2016 16:41:23 +0530
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On Wednesday 13 April 2016 05:30 AM, Peter Hurley wrote:

>>> - generates spurious uart interrupt for every rx dma transaction
>>>   (ie., necessitates acking every UART interrupt, even UART_IIR_NO_INT)
>>>   _Even with this workaround_, it still generates spurious interrupt warning
>>>   which shuts off interrupts for several ms while logging the error
>>>   message to the console, virtually guaranteeing lost data.
>>
>> as I wrote in my other email I think RDI should be disabled with DMA
> 
> 
> I'll test to see if disabling RDI eliminates the UART_IIR_NO_INT spurious
> interrupts.
> 
>> according the Intel manual and I *think* someone here reported that
>> they see the same problem.
> 
> Let's confirm with the Intel folks that this is true, which would argue
> for using the omap-style rx dma flow.

Andy Shevchenko pointed this out here: https://lkml.org/lkml/2016/2/23/588

Regards,
Sekhar