From 37f36d894ef43dc2986d0936612ec967c5a89be8 Mon Sep 17 00:00:00 2001 From: Tomasz Wroblewski Date: Wed, 28 Aug 2013 10:19:42 +0200 Subject: PCI UART: better cope with UART being temporarily unavailable This happens for example when dom0 disables ioport responses during PCI subsystem initialisation. If a __ns16550_poll() happens to be scheduled during that time, Xen hangs. Detect and exit that condition. Amended ns16550_ioport_invalid function to only check IER register, which contins 3 reserved (always 0) bits, therefore it's sufficient for that test. Signed-off-by: Tomasz Wroblewski Acked-by: Keir Fraser --- xen/drivers/char/ehci-dbgp.c | 2 +- xen/drivers/char/ns16550.c | 27 ++++++++++++++++----------- xen/drivers/char/serial.c | 38 +++++++++++++++++++++++++------------- 3 files changed, 42 insertions(+), 25 deletions(-) (limited to 'xen/drivers') diff --git a/xen/drivers/char/ehci-dbgp.c b/xen/drivers/char/ehci-dbgp.c index bead374bc8..25049796e2 100644 --- a/xen/drivers/char/ehci-dbgp.c +++ b/xen/drivers/char/ehci-dbgp.c @@ -1204,7 +1204,7 @@ static void ehci_dbgp_putc(struct serial_port *port, char c) ehci_dbgp_flush(port); } -static unsigned int ehci_dbgp_tx_ready(struct serial_port *port) +static int ehci_dbgp_tx_ready(struct serial_port *port) { struct ehci_dbgp *dbgp = port->uart; diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c index ddca62fccf..e0f80f6d18 100644 --- a/xen/drivers/char/ns16550.c +++ b/xen/drivers/char/ns16550.c @@ -75,6 +75,11 @@ static void ns_write_reg(struct ns16550 *uart, int reg, char c) writeb(c, uart->remapped_io_base + reg); } +static int ns16550_ioport_invalid(struct ns16550 *uart) +{ + return (unsigned char)ns_read_reg(uart, UART_IER) == 0xff; +} + static void ns16550_interrupt( int irq, void *dev_id, struct cpu_user_regs *regs) { @@ -105,11 +110,17 @@ static void __ns16550_poll(struct cpu_user_regs *regs) return; /* Interrupts work - no more polling */ while ( ns_read_reg(uart, UART_LSR) & UART_LSR_DR ) + { + if ( ns16550_ioport_invalid(uart) ) + goto out; + serial_rx_interrupt(port, regs); + } if ( ns_read_reg(uart, UART_LSR) & UART_LSR_THRE ) serial_tx_interrupt(port, regs); +out: set_timer(&uart->timer, NOW() + MILLISECS(uart->timeout_ms)); } @@ -123,10 +134,12 @@ static void ns16550_poll(void *data) #endif } -static unsigned int ns16550_tx_ready(struct serial_port *port) +static int ns16550_tx_ready(struct serial_port *port) { struct ns16550 *uart = port->uart; + if ( ns16550_ioport_invalid(uart) ) + return -EIO; return ns_read_reg(uart, UART_LSR) & UART_LSR_THRE ? uart->fifo_size : 0; } @@ -140,7 +153,8 @@ static int ns16550_getc(struct serial_port *port, char *pc) { struct ns16550 *uart = port->uart; - if ( !(ns_read_reg(uart, UART_LSR) & UART_LSR_DR) ) + if ( ns16550_ioport_invalid(uart) || + !(ns_read_reg(uart, UART_LSR) & UART_LSR_DR) ) return 0; *pc = ns_read_reg(uart, UART_RBR); @@ -308,15 +322,6 @@ static void _ns16550_resume(struct serial_port *port) ns16550_setup_postirq(port->uart); } -static int ns16550_ioport_invalid(struct ns16550 *uart) -{ - return ((((unsigned char)ns_read_reg(uart, UART_LSR)) == 0xff) && - (((unsigned char)ns_read_reg(uart, UART_MCR)) == 0xff) && - (((unsigned char)ns_read_reg(uart, UART_IER)) == 0xff) && - (((unsigned char)ns_read_reg(uart, UART_IIR)) == 0xff) && - (((unsigned char)ns_read_reg(uart, UART_LCR)) == 0xff)); -} - static int delayed_resume_tries; static void ns16550_delayed_resume(void *data) { diff --git a/xen/drivers/char/serial.c b/xen/drivers/char/serial.c index cd0b864374..9b006f2f7f 100644 --- a/xen/drivers/char/serial.c +++ b/xen/drivers/char/serial.c @@ -59,7 +59,7 @@ void serial_rx_interrupt(struct serial_port *port, struct cpu_user_regs *regs) void serial_tx_interrupt(struct serial_port *port, struct cpu_user_regs *regs) { - unsigned int i, n; + int i, n; unsigned long flags; local_irq_save(flags); @@ -71,7 +71,7 @@ void serial_tx_interrupt(struct serial_port *port, struct cpu_user_regs *regs) */ while ( !spin_trylock(&port->tx_lock) ) { - if ( !port->driver->tx_ready(port) ) + if ( port->driver->tx_ready(port) <= 0 ) goto out; cpu_relax(); } @@ -111,15 +111,18 @@ static void __serial_putc(struct serial_port *port, char c) if ( port->tx_log_everything ) { /* Buffer is full: we spin waiting for space to appear. */ - unsigned int n; + int n; while ( (n = port->driver->tx_ready(port)) == 0 ) cpu_relax(); - while ( n-- ) - port->driver->putc( - port, - port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]); - port->txbuf[mask_serial_txbuf_idx(port->txbufp++)] = c; + if ( n > 0 ) + { + while ( n-- ) + port->driver->putc( + port, + port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]); + port->txbuf[mask_serial_txbuf_idx(port->txbufp++)] = c; + } } else { @@ -130,9 +133,9 @@ static void __serial_putc(struct serial_port *port, char c) } if ( ((port->txbufp - port->txbufc) == 0) && - port->driver->tx_ready(port) ) + port->driver->tx_ready(port) > 0 ) { - /* Buffer and UART FIFO are both empty. */ + /* Buffer and UART FIFO are both empty, and port is available. */ port->driver->putc(port, c); } else @@ -143,10 +146,13 @@ static void __serial_putc(struct serial_port *port, char c) } else if ( port->driver->tx_ready ) { + int n; + /* Synchronous finite-capacity transmitter. */ - while ( !port->driver->tx_ready(port) ) + while ( !(n = port->driver->tx_ready(port)) ) cpu_relax(); - port->driver->putc(port, c); + if ( n > 0 ) + port->driver->putc(port, c); } else { @@ -390,8 +396,14 @@ void serial_start_sync(int handle) { while ( (port->txbufp - port->txbufc) != 0 ) { - while ( !port->driver->tx_ready(port) ) + int n; + + while ( !(n = port->driver->tx_ready(port)) ) cpu_relax(); + if ( n < 0 ) + /* port is unavailable and might not come up until reenabled by + dom0, we can't really do proper sync */ + break; port->driver->putc( port, port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]); } -- cgit v1.2.3