[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v1] xen/arm: Manage pl011 uart TX interrupt correctly
From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx> In pl011.c, when TX interrupt is received serial_tx_interrupt() is called to push next characters. If TX buffer is empty, serial_tx_interrupt() does not disable TX interrupt and hence pl011 UART irq handler pl011_interrupt() always sees TX interrupt status set in MIS register and cpu does not come out of UART irq handler. With this patch, mask TX interrupt by writing 0 to IMSC register when TX buffer is empty and unmask by writing 1 to IMSC register before sending characters. Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx> --- xen/drivers/char/pl011.c | 16 ++++++++++++++++ xen/drivers/char/serial.c | 34 ++++++++++++++++++++++++++++++++++ xen/include/xen/serial.h | 4 ++++ 3 files changed, 54 insertions(+) diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c index dd19ce8..57274d9 100644 --- a/xen/drivers/char/pl011.c +++ b/xen/drivers/char/pl011.c @@ -197,6 +197,20 @@ static const struct vuart_info *pl011_vuart(struct serial_port *port) return &uart->vuart; } +static void pl011_tx_stop(struct serial_port *port) +{ + struct pl011 *uart = port->uart; + + pl011_write(uart, IMSC, pl011_read(uart, IMSC) & ~(TXI)); +} + +static void pl011_tx_start(struct serial_port *port) +{ + struct pl011 *uart = port->uart; + + pl011_write(uart, IMSC, pl011_read(uart, IMSC) | (TXI)); +} + static struct uart_driver __read_mostly pl011_driver = { .init_preirq = pl011_init_preirq, .init_postirq = pl011_init_postirq, @@ -207,6 +221,8 @@ static struct uart_driver __read_mostly pl011_driver = { .putc = pl011_putc, .getc = pl011_getc, .irq = pl011_irq, + .start_tx = pl011_tx_start, + .stop_tx = pl011_tx_stop, .vuart_info = pl011_vuart, }; diff --git a/xen/drivers/char/serial.c b/xen/drivers/char/serial.c index 44026b1..c583a48 100644 --- a/xen/drivers/char/serial.c +++ b/xen/drivers/char/serial.c @@ -31,6 +31,18 @@ static struct serial_port com[SERHND_IDX + 1] = { static bool_t __read_mostly post_irq; +static inline void serial_start_tx(struct serial_port *port) +{ + if ( port->driver->start_tx != NULL ) + port->driver->start_tx(port); +} + +static inline void serial_stop_tx(struct serial_port *port) +{ + if ( port->driver->stop_tx != NULL ) + port->driver->stop_tx(port); +} + void serial_rx_interrupt(struct serial_port *port, struct cpu_user_regs *regs) { char c; @@ -76,6 +88,18 @@ void serial_tx_interrupt(struct serial_port *port, struct cpu_user_regs *regs) cpu_relax(); } + if ( port->txbufc == port->txbufp ) + { + /* Disable TX. nothing to send */ + serial_stop_tx(port); + spin_unlock(&port->tx_lock); + goto out; + } + else + { + if ( port->driver->tx_ready(port) ) + serial_start_tx(port); + } for ( i = 0, n = port->driver->tx_ready(port); i < n; i++ ) { if ( port->txbufc == port->txbufp ) @@ -117,6 +141,8 @@ static void __serial_putc(struct serial_port *port, char c) cpu_relax(); if ( n > 0 ) { + /* Enable TX before sending chars */ + serial_start_tx(port); while ( n-- ) port->driver->putc( port, @@ -135,6 +161,8 @@ static void __serial_putc(struct serial_port *port, char c) if ( ((port->txbufp - port->txbufc) == 0) && port->driver->tx_ready(port) > 0 ) { + /* Enable TX before sending chars */ + serial_start_tx(port); /* Buffer and UART FIFO are both empty, and port is available. */ port->driver->putc(port, c); } @@ -152,11 +180,16 @@ static void __serial_putc(struct serial_port *port, char c) while ( !(n = port->driver->tx_ready(port)) ) cpu_relax(); if ( n > 0 ) + { + /* Enable TX before sending chars */ + serial_start_tx(port); port->driver->putc(port, c); + } } else { /* Simple synchronous transmitter. */ + serial_start_tx(port); port->driver->putc(port, c); } } @@ -404,6 +437,7 @@ void serial_start_sync(int handle) /* port is unavailable and might not come up until reenabled by dom0, we can't really do proper sync */ break; + serial_start_tx(port); port->driver->putc( port, port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]); } diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h index 9f4451b..71e6ade 100644 --- a/xen/include/xen/serial.h +++ b/xen/include/xen/serial.h @@ -81,6 +81,10 @@ struct uart_driver { int (*getc)(struct serial_port *, char *); /* Get IRQ number for this port's serial line: returns -1 if none. */ int (*irq)(struct serial_port *); + /* Unmask TX interrupt */ + void (*start_tx)(struct serial_port *); + /* Mask TX interrupt */ + void (*stop_tx)(struct serial_port *); /* Get serial information */ const struct vuart_info *(*vuart_info)(struct serial_port *); }; -- 1.7.9.5 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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