diff options
Diffstat (limited to 'xen/drivers/char/ns16550.c')
| -rw-r--r-- | xen/drivers/char/ns16550.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c index 45da924381..5892eb7a85 100644 --- a/xen/drivers/char/ns16550.c +++ b/xen/drivers/char/ns16550.c @@ -61,6 +61,7 @@ static struct ns16550 { struct timer resume_timer; unsigned int timeout_ms; bool_t intr_works; + bool_t dw_usr_bsy; #ifdef HAS_PCI /* PCI card parameters. */ unsigned int pb_bdf[3]; /* pci bridge BDF */ @@ -237,6 +238,16 @@ static void ns16550_setup_preirq(struct ns16550 *uart) /* No interrupts. */ ns_write_reg(uart, UART_IER, 0); + if ( uart->dw_usr_bsy && + (ns_read_reg(uart, UART_IIR) & UART_IIR_BSY) == UART_IIR_BSY ) + { + /* DesignWare 8250 detects if LCR is written while the UART is + * busy and raises a "busy detect" interrupt. Read the UART + * Status Register to clear this state. + */ + ns_read_reg(uart, UART_USR); + } + /* Line control and baud-rate generator. */ ns_write_reg(uart, UART_LCR, lcr | UART_LCR_DLAB); if ( uart->baud != BAUD_AUTO ) @@ -787,6 +798,8 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev, /* The common bit of the driver mostly deals with irq not dt_irq. */ uart->irq = uart->dt_irq.irq; + uart->dw_usr_bsy = dt_device_is_compatible(dev, "snps,dw-apb-uart"); + uart->vuart.base_addr = uart->io_base; uart->vuart.size = uart->io_size; uart->vuart.data_off = UART_THR <<uart->reg_shift; @@ -804,6 +817,7 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev, static const char const *ns16550_dt_compat[] __initconst = { "ns16550", + "snps,dw-apb-uart", NULL }; |