From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Sekhar Nori <nsekhar@ti.com>,
John Ogness <john.ogness@linutronix.de>,
Tony Lindgren <tony@atomide.com>
Cc: Peter Hurley <peter@hurleysoftware.com>,
gregkh@linuxfoundation.org, vinod.koul@intel.com,
dan.j.williams@intel.com, peter.ujfalusi@ti.com,
dmaengine@vger.kernel.org, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] serial: omap: robustify for high speed transfers
Date: Tue, 23 Feb 2016 13:43:53 +0100 [thread overview]
Message-ID: <56CC5409.2050609@linutronix.de> (raw)
In-Reply-To: <56CC2D83.3090900@ti.com>
On 02/23/2016 10:59 AM, Sekhar Nori wrote:
>> With the am335x (Beaglebone Black, eDMA engine) I see 1000 DMA
>> interrupts and 1000 spurious UART interrupts. The spurious UART
>> interrupts arrive 30-50us _before_ the DMA interrupts. Always.
>>
>> If I disable UART timeout interrupts (RDI), the same test generates no
>> spurious UART interrupts. Only 1000 DMA interrupts.
>
> To be clear, these interrupts are not caught as spurious by the
> interrupt controller (INTC). They are detected by INTC as UART
> interrupts. Just that you don't expect a timeout interrupt to happen at
> the time you see the interrupt, correct?
>From what I remember the INTC says it is UART, correct.
But UART's status register says "no interrupt" (IIR has UART_IIR_NO_INT
set). So the UART driver returns IRQ_NONE which counts as spurious.
It is just that once you disable RDI there are no more interrupts coming
during DMA transfer.
> Thanks,
> Sekhar
>
Sebastian
next prev parent reply other threads:[~2016-02-23 12:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-22 10:27 [PATCH 0/4] serial: omap: robustify for high speed transfers John Ogness
2016-01-22 10:27 ` John Ogness
2016-01-25 18:56 ` Peter Hurley
2016-01-29 16:35 ` John Ogness
2016-02-03 1:21 ` Peter Hurley
2016-02-11 12:02 ` John Ogness
2016-02-11 21:00 ` Tony Lindgren
2016-02-22 15:30 ` John Ogness
2016-02-22 19:38 ` Tony Lindgren
2016-02-23 9:59 ` Sekhar Nori
2016-02-23 9:59 ` Sekhar Nori
2016-02-23 12:43 ` Sebastian Andrzej Siewior [this message]
2016-02-23 16:56 ` Andy Shevchenko
2016-02-24 3:20 ` Peter Hurley
2016-02-24 15:37 ` Sekhar Nori
2016-02-24 15:37 ` Sekhar Nori
2016-02-24 15:46 ` Sebastian Andrzej Siewior
2016-03-07 20:23 ` Peter Hurley
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