sounds very much like this issue: http://linux.derkeiler.com/Mailing-Lists/Kernel/2010-02/msg09470.html (interrupt storm on the second port which is hit with breaks). It's not the uart driver problem per se, the below fixes it: *** linux/drivers/serial/serial_core.c#1 Wed Feb 24 17:46:22 2010 --- linux/drivers/serial/serial_core.c#2 Mon Mar 1 15:00:29 2010 *************** *** 622,632 **** struct uart_port *port = state->port; if (I_IXOFF(tty)) { if (port->x_char) port->x_char = 0; ! else uart_send_xchar(tty, START_CHAR(tty)); } if (tty->termios->c_cflag & CRTSCTS) uart_set_mctrl(port, TIOCM_RTS); --- 622,632 ---- struct uart_port *port = state->port; if (I_IXOFF(tty)) { if (port->x_char) port->x_char = 0; ! else if (!(tty->flags & (1 << TTY_IO_ERROR))) uart_send_xchar(tty, START_CHAR(tty)); } if (tty->termios->c_cflag & CRTSCTS) uart_set_mctrl(port, TIOCM_RTS); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ I did not get to trying to submit it, but it sure gets rid o the storm. cheers, /vb On Fri, Feb 26, 2010 at 11:25 AM, Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> wrote: > Sending a break on the SOC UARTs found in some MPC83xx/85xx/86xx > chips seems to cause a short lived IRQ storm (/proc/interrupts > typically shows somewhere between 300 and 1500 events). Unfortunately > this renders SysRQ over the serial console completely inoperable. > Testing with obvious things like ACKing the event doesn't seem to > change anything vs. a completely dumb approach of just ignoring > it and waiting for it to stop, so that is what is implemented here. > > Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> > --- > > This is a refresh of a patch I'd done earlier -- I've tried to make > the bug support as generic as possible to minimize having board > specific ifdef crap in 8250.c -- any suggestions on how to further > improve it are welcome. > > drivers/serial/8250.c | 6 ++++++ > drivers/serial/8250.h | 20 ++++++++++++++++++++ > drivers/serial/Kconfig | 14 ++++++++++++++ > include/linux/serial_reg.h | 2 ++ > 4 files changed, 42 insertions(+), 0 deletions(-) > > diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c > index e9b15c3..850b0e9 100644 > --- a/drivers/serial/8250.c > +++ b/drivers/serial/8250.c > @@ -1531,6 +1531,11 @@ static void serial8250_handle_port(struct uart_8250_port *up) > > status = serial_inp(up, UART_LSR); > > + if ((up->bugs & UART_BUG_PPC) && (status == UART_LSR_RFE_ERROR_BITS)) { > + spin_unlock_irqrestore(&up->port.lock, flags); > + return; > + } > + > DEBUG_INTR("status = %x...", status); > > if (status & (UART_LSR_DR | UART_LSR_BI)) > @@ -1948,6 +1953,7 @@ static int serial8250_startup(struct uart_port *port) > > up->capabilities = uart_config[up->port.type].flags; > up->mcr = 0; > + up->bugs |= UART_KNOWN_BUGS; > > if (up->port.iotype != up->cur_iotype) > set_io_from_upio(port); > diff --git a/drivers/serial/8250.h b/drivers/serial/8250.h > index 6e19ea3..2074ce1 100644 > --- a/drivers/serial/8250.h > +++ b/drivers/serial/8250.h > @@ -49,6 +49,7 @@ struct serial8250_config { > #define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */ > #define UART_BUG_NOMSR (1 << 2) /* UART has buggy MSR status bits (Au1x00) */ > #define UART_BUG_THRE (1 << 3) /* UART has buggy THRE reassertion */ > +#define UART_BUG_PPC (1 << 4) /* UART has buggy PPC break IRQ storm */ > > #define PROBE_RSA (1 << 0) > #define PROBE_ANY (~0) > @@ -78,3 +79,22 @@ struct serial8250_config { > #else > #define ALPHA_KLUDGE_MCR 0 > #endif > + > +/* > + * The following UART bugs are currently dynamically detected and not > + * required to be contingent on any particular compile time options. > + */ > +#define HAS_BUG_QUOT 0 /* assign UART_BUG_QUOT to enable */ > +#define HAS_BUG_TXEN 0 /* assign UART_BUG_TXEN to enable */ > +#define HAS_BUG_NOMSR 0 /* assign UART_BUG_NOMSR to enable */ > +#define HAS_BUG_THRE 0 /* assign UART_BUG_THRE to enable */ > + > +#ifdef CONFIG_SERIAL_8250_PPC_BUG > +#define HAS_BUG_PPC UART_BUG_PPC > +#else > +#define HAS_BUG_PPC 0 > +#endif > + > +#define UART_KNOWN_BUGS (HAS_BUG_QUOT | HAS_BUG_TXEN | HAS_BUG_NOMSR | \ > + HAS_BUG_THRE | HAS_BUG_PPC) > + > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig > index 9ff47db..e01a411 100644 > --- a/drivers/serial/Kconfig > +++ b/drivers/serial/Kconfig > @@ -70,6 +70,20 @@ config SERIAL_8250_CONSOLE > > If unsure, say N. > > +config SERIAL_8250_PPC_BUG > + bool "Fix 8250/16550 to handle IRQ storm after receipt of a break" > + depends on SERIAL_8250 && PPC32 > + ---help--- > + If you say Y here, addional checks will be added in the handling of > + interrupts on the serial ports which will prevent ill effects of > + an interrupt storm triggered by a break on the serial line. Without > + this enabled, a Sysrq via the serial console can be unusable on > + some systems. > + > + This is commonly observed on PPC32 MPC83xx/85xx/86xx based boards. > + > + If unsure, say N. > + > config FIX_EARLYCON_MEM > bool > depends on X86 > diff --git a/include/linux/serial_reg.h b/include/linux/serial_reg.h > index cf9327c..010174f 100644 > --- a/include/linux/serial_reg.h > +++ b/include/linux/serial_reg.h > @@ -111,6 +111,7 @@ > #define UART_MCR_DTR 0x01 /* DTR complement */ > > #define UART_LSR 5 /* In: Line Status Register */ > +#define UART_LSR_RFE 0x80 /* Rx FIFO Error (BE, FE, or PE) */ > #define UART_LSR_TEMT 0x40 /* Transmitter empty */ > #define UART_LSR_THRE 0x20 /* Transmit-hold-register empty */ > #define UART_LSR_BI 0x10 /* Break interrupt indicator */ > @@ -119,6 +120,7 @@ > #define UART_LSR_OE 0x02 /* Overrun error indicator */ > #define UART_LSR_DR 0x01 /* Receiver data ready */ > #define UART_LSR_BRK_ERROR_BITS 0x1E /* BI, FE, PE, OE bits */ > +#define UART_LSR_RFE_ERROR_BITS 0xF1 /* RFE, TEMT, THRE, BI, DR bits */ > > #define UART_MSR 6 /* In: Modem Status Register */ > #define UART_MSR_DCD 0x80 /* Data Carrier Detect */ > -- > 1.6.5.2 > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@xxxxxxxxxxxxxxxx > https://lists.ozlabs.org/listinfo/linuxppc-dev > -- 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
