linux-kernel - Re: [PATCH 0/4] serial: omap: robustify for high speed transfers

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Message-ID: <20160211210050.GY19432@atomide.com>
Date:	Thu, 11 Feb 2016 13:00:50 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	John Ogness <john.ogness@...utronix.de>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	gregkh@...uxfoundation.org, vinod.koul@...el.com,
	dan.j.williams@...el.com, bigeasy@...utronix.de, nsekhar@...com,
	peter.ujfalusi@...com, dmaengine@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] serial: omap: robustify for high speed transfers

Hi,

* John Ogness <john.ogness@...utronix.de> [160211 04:04]:
> 
> At these speeds, nearly every DMA interrupt is accompanied by a spurious
> UART interrupt. So, sadly, the interrupts are doubled.
> 
> It is on my TODO list to verify if the spurious UART interrupts exactly
> match the recently added [0] spurious interrupt detection in omap-intc.

If you're seeing spurious interrupts you may want try adding
a flush of posted write at the end of the 8250_omap interrupt
handler. Basically read back some register from the 8250. This
has fixed so far pretty much all the spurious IRQ issues for
omaps using the drivers/irqchip/irq-omap-intc.c, meaning omap3
and am335x and ti81xx variants too most likely.

Regards,

Tony