From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frans Klaver Subject: Re: [RFC PATCH 3/4] tty: omap-serial: use threaded interrupt handler Date: Thu, 21 Aug 2014 23:41:17 +0200 Message-ID: <20140821214117.GA7076@ci00147.xsens-tech.local> References: <1406645577-18620-1-git-send-email-frans.klaver@xsens.com> <1408450488-4083-1-git-send-email-frans.klaver@xsens.com> <1408450488-4083-4-git-send-email-frans.klaver@xsens.com> <20140819185701.GC22003@saruman.home> <20140820064028.GC9319@ci00147.xsens-tech.local> <20140820160604.GH24500@saruman.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Return-path: Received: from filter1.ibarracuda.nl ([83.247.7.10]:56358 "EHLO filter1.ibarracuda.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755066AbaHUVlW (ORCPT ); Thu, 21 Aug 2014 17:41:22 -0400 Content-Disposition: inline In-Reply-To: <20140820160604.GH24500@saruman.home> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Felipe Balbi Cc: Tony Lindgren , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Greg Kroah-Hartman , Alexey Pelykh , Jiri Slaby , Frans Klaver , linux-serial@vger.kernel.org, linux-omap@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org On Wed, Aug 20, 2014 at 11:06:05AM -0500, Felipe Balbi wrote: > On Wed, Aug 20, 2014 at 08:40:28AM +0200, Frans Klaver wrote: > > On Tue, Aug 19, 2014 at 01:57:02PM -0500, Felipe Balbi wrote: > > > On Tue, Aug 19, 2014 at 02:14:47PM +0200, Frans Klaver wrote: > > > > At 3.6Mbaud, with slightly over 2Mbit/s data coming in, we see 1600 uart > > > > rx buffer overflows within 30 seconds. Threading the interrupt handling reduces > > > > this to about 170 overflows in 10 minutes. > > > > > > Can you try Sebastian Siewior's patches for 8250_omap and 8250 dma > > > support ? That should help you a lot. > > > > I'll have a look at that series. Thanks for pointing it out. I have had a look at Sebastian's series, but I'm not convinced yet that we should use it. So far the serial console seems to be missing data every now and then. I haven't gotten around to testing our high traffic application yet. > > > > drivers/tty/serial/omap-serial.c | 31 ++++++++++++++++++++++++------- > > > > 1 file changed, 24 insertions(+), 7 deletions(-) > > > > > > > > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c > > > > index 14a0167..57664b9 100644 > > > > --- a/drivers/tty/serial/omap-serial.c > > > > +++ b/drivers/tty/serial/omap-serial.c > > > > @@ -575,6 +575,21 @@ static void serial_omap_rdi(struct uart_omap_port *up, unsigned int lsr) > > > > } > > > > > > > > /** > > > > + * serial_omap_fast_irq() - schedule interrupt handling > > > > + */ > > > > +static irqreturn_t serial_omap_fast_irq(int irq, void *dev_id) > > > > +{ > > > > + struct uart_omap_port *up = dev_id; > > > > + unsigned int iir = serial_in(up, UART_IIR); > > > > + > > > > + if (iir & UART_IIR_NO_INT) > > > > + return IRQ_NONE; > > > > + > > > > + disable_irq_nosync(up->port.irq); > > > > > > NAK. Either use IRQF_ONESHOT or actually mask the IRQs at the device's > > > registers (basically clearing IER). > > > > Given the work that's been done on the 8250 based driver, what are the > > short-term chances omap-serial will be dropped? I'd be happy to improve > > here if it makes sense to do so. If the 8250 based driver is going to > > replace omap-serial anyway on the short term, I don't see the point of > > further developing this patch. The others would still make sense in my > > opinion. > > if we find a way to maintain the same ttyO* naming scheme and make it > coexist with ttyS* naming, then we could drop as soon as 8250_omap is > ready for prime time. With that in mind, for now I'll be betting on two horses. I'll cook up a new version using oneshot. Thanks, Frans