Hi, 2010/10/29 Aras Vaichas <arasv@xxxxxxxxxxxxxxxxxxxxxxx>: >> > On AT91 David Brownell noticed several months >> > ago that the DBGU can miss some characters on NO_HZ. I would expect >> > that this would be better now due to the shorter interrupt handler, >> > although it was not my goal to solve it with these patches. >> The current (kernel.org git) AT91 timer handler incorporates a bugfix >> in that area, which seemed to resolve most of those problems. >> - Dave > > Hello, > > I'm sorry to bother you two off-list, but I'm trying to avoid too much > noise on the lists. Please, always at least CC to the mailinglist as well. > My issue is related to these two posts (and the re: above): > > http://www.mail-archive.com/linux-rt-users@xxxxxxxxxxxxxxx/msg02115.html > http://permalink.gmane.org/gmane.linux.ports.arm.kernel/94652 > > If I change the Atmel serial interrupt to IRQF_NODELAY, then *most* of > the overruns go away and DBGU works as it should. > > --- A/drivers/serial/atmel_serial.c 2010-08-03 03:27:18.000000000 +1000 > +++ B/drivers/serial/atmel_serial.c 2010-10-29 10:24:54.000000000 +1100 > @@ -808,7 +818,7 @@ > /* > * Allocate the IRQ > */ > - retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED, > + retval = request_irq(port->irq, atmel_interrupt, IRQF_NODELAY, > tty ? tty->name : "atmel_serial", port); > if (retval) { > printk("atmel_serial: atmel_startup - Can't get irq\n"); > > > But shouldn't the DBGU interrupt already be running in NODELAY context > according to Remy's post? I understand that NODELAY has many other > complications, this is just a test to get an idea of which direction > to move in. On preempt-RT this driver always has NODELAY set by default. AFAIK, it is not in mainline. Notice that on recent kernels also the request_threaded_irq() mechanism can be used, which is much cleaner compared to the NODELAY change. So, I guess the NODELAY change will never hit mainline since this better solution exist. Kind regards, Remy -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
