Hi Taichi, On 06/05/2015 06:03 AM, Taichi Kageyama wrote: > This patch provides a new parameter as a workaround of the following > problem. It allows us to skip autoconfig_irq() and to use a well-known irq > number for a console even if CONFIG_SERIAL_8250_DETECT_IRQ is defined. > > There're cases where autoconfig_irq() fails during boot. > In these cases, the console doesn't work in interrupt mode, > the mode cannot be changed anymore, and "input overrun" > (which can make operation mistakes) happens easily. > This problem happens with high rate every boot once it occurs > because the boot sequence is always almost same. > > autoconfig_irq() assumes that a CPU can handle an interrupt from a serial > during the waiting time, but there're some cases where the CPU cannot > handle the interrupt for longer than the time. It completely depends on > how other functions work on the CPU. Ideally, autoconfig_irq() should be > fixed It completely depends on how long some other driver has interrupts disabled, which is a problem that needs fixed _in that driver_. autoconfig_irq() does not need fixing. A typical cause of this behavior is printk spew from overly-instrumented debugging of some driver (trace_printk is better suited to heavy instrumentation). Regards, Peter Hurley > to control these cases but as long as auto_irq algorithm is used, > it's hard to know which CPU can handle an interrupt from a serial and > to assure the interrupt of the CPU is enabled during auto_irq. > Meanwhile for legacy consoles, they actually don't require auto_irq > because they basically use well-known irq number. > For non-console serials, this workaround is not required > because setserial command can kick autoconfig_irq() again for them. > > Signed-off-by: Taichi Kageyama <t-kageyama@xxxxxxxxxxxxx> > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > --- > drivers/tty/serial/8250/8250_core.c | 17 +++++++++++++++++ > 1 files changed, 17 insertions(+), 0 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > index 6bf31f2..60fda28 100644 > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -65,6 +65,8 @@ static int serial_index(struct uart_port *port) > > static unsigned int skip_txen_test; /* force skip of txen test at init time */ > > +static unsigned int skip_cons_autoirq; /* force skip autoirq for console */ > + > /* > * Debugging. > */ > @@ -3336,6 +3338,9 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) > if (skip_txen_test) > up->port.flags |= UPF_NO_TXEN_TEST; > > + if (uart_console(&up->port) && skip_cons_autoirq) > + up->port.flags &= ~UPF_AUTO_IRQ; > + > uart_add_one_port(drv, &up->port); > } > } > @@ -3875,6 +3880,9 @@ int serial8250_register_8250_port(struct uart_8250_port *up) > if (skip_txen_test) > uart->port.flags |= UPF_NO_TXEN_TEST; > > + if (uart_console(&uart->port) && skip_cons_autoirq) > + uart->port.flags &= ~UPF_AUTO_IRQ; > + > if (up->port.flags & UPF_FIXED_TYPE) > uart->port.type = up->port.type; > > @@ -3936,6 +3944,10 @@ void serial8250_unregister_port(int line) > uart->port.flags &= ~UPF_BOOT_AUTOCONF; > if (skip_txen_test) > uart->port.flags |= UPF_NO_TXEN_TEST; > + > + if (uart_console(&uart->port) && skip_cons_autoirq) > + uart->port.flags &= ~UPF_AUTO_IRQ; > + > uart->port.type = PORT_UNKNOWN; > uart->port.dev = &serial8250_isa_devs->dev; > uart->capabilities = 0; > @@ -4044,6 +4056,9 @@ MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STR > module_param(skip_txen_test, uint, 0644); > MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time"); > > +module_param(skip_cons_autoirq, uint, 0644); > +MODULE_PARM_DESC(skip_cons_autoirq, "Skip auto irq for console during boot"); > + > #ifdef CONFIG_SERIAL_8250_RSA > module_param_array(probe_rsa, ulong, &probe_rsa_count, 0444); > MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA"); > @@ -4070,6 +4085,8 @@ static void __used s8250_options(void) > module_param_cb(share_irqs, ¶m_ops_uint, &share_irqs, 0644); > module_param_cb(nr_uarts, ¶m_ops_uint, &nr_uarts, 0644); > module_param_cb(skip_txen_test, ¶m_ops_uint, &skip_txen_test, 0644); > + module_param_cb(skip_cons_autoirq, ¶m_ops_uint, > + &skip_cons_autoirq, 0644); > #ifdef CONFIG_SERIAL_8250_RSA > __module_param_call(MODULE_PARAM_PREFIX, probe_rsa, > ¶m_array_ops, .arr = &__param_arr_probe_rsa, > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
