From: Sekhar Nori Subject: Re: omap uart + dma issues (Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes) Date: Wed, 13 Apr 2016 16:41:23 +0530 Message-ID: <570E295B.2030708@ti.com> References: <8737r7ght7.fsf@linutronix.de> <570339E8.6010808@hurleysoftware.com> <87y48kftip.fsf@linutronix.de> <570BE48F.60801@hurleysoftware.com> <570BED7B.9080803@linutronix.de> <570C04C1.40201@hurleysoftware.com> <570D2A46.2050106@linutronix.de> <570D8C16.1010702@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <570D8C16.1010702@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org To: Peter Hurley , Sebastian Andrzej Siewior , John Ogness , Tony Lindgren Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-omap@vger.kernel.org, Andy Shevchenko List-Id: linux-omap@vger.kernel.org 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