On Mon, Mar 27, 2023 at 06:11:12PM +0300, Sergey Organov wrote: > Stefan Wahren <stefan.wahren@xxxxxxxx> writes: > > > Hi, > > > > Am 25.03.23 um 16:11 schrieb Uwe Kleine-König: > > [...] > > > today i had time to do some testing. At first i tested with different RXTL_DEFAULT values. > > > > 1 No overrun > > 2 No overrun > > 4 No overrun > > 8 Overruns > > > > After that i look at the # echo 0 > /proc/sys/kernel/printk approach, > > but this didn't change anything. The kernel is usually silent about > > log message after boot and the console works still with echo. > > Enforcing some driver to call printk periodically would make the > > console unusuable. > > As you figured that printk() is not the cause, it must be something else > that causes overruns, so there is no need to check printk case further. > > > > > Finally i tried to disabled the spin_lock in imx_uart_console_write: > > > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c > > index f07c4f9ff13c..c342559ff1a2 100644 > > --- a/drivers/tty/serial/imx.c > > +++ b/drivers/tty/serial/imx.c > > @@ -2007,14 +2007,12 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) > > struct imx_port_ucrs old_ucr; > > unsigned long flags; > > unsigned int ucr1; > > - int locked = 1; > > + int locked = 0; > > > > if (sport->port.sysrq) > > locked = 0; > > else if (oops_in_progress) > > locked = spin_trylock_irqsave(&sport->port.lock, flags); > > - else > > - spin_lock_irqsave(&sport->port.lock, flags); > > > > /* > > * First, save UCR1/2/3 and then disable interrupts > > > > But the overruns still occured. Is this because the serial core > > already helds a lock? > > This probably isn't even called when there is no printk() output, as > user-space writes to /dev/console are rather performed through regular > generic code, AFAIK. Correct on both points. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
