[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] pl011: preserve RTS and DTR signal on UART init
On Tue, 2013-09-03 at 16:00 +0200, Andre Przywara wrote: > Although we do not support hardware flow control in the Xen driver > for the PL011 UART, the other end may be configured to use it. > In this case it waits in vain for the RTS signal to be asserted by > the host and will never transmit any characters. > So we leave RTS and DTR as they had been setup before. > This fixes the UART input on Calxeda Midway, which uses hardware > flow control for the serial-over-LAN functionality. > > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx> Acked + applied, thanks. I wonder if we should turn of RXE/TXE/UARTEN early on before we do our own setup? Just to get things in a known quiet state. Although if this was going to be a problem it would have bit us all the way through boot... > --- > xen/drivers/char/pl011.c | 7 +++++-- > xen/include/asm-arm/pl011-uart.h | 4 ++++ > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c > index 3ec6e10..3386e2b 100644 > --- a/xen/drivers/char/pl011.c > +++ b/xen/drivers/char/pl011.c > @@ -85,6 +85,7 @@ static void __init pl011_init_preirq(struct serial_port > *port) > { > struct pl011 *uart = port->uart; > unsigned int divisor; > + unsigned int cr; > > /* No interrupts, please. */ > pl011_write(uart, IMSC, 0); > @@ -120,8 +121,10 @@ static void __init pl011_init_preirq(struct serial_port > *port) > pl011_write(uart, IMSC, 0); > pl011_write(uart, ICR, ALLI); > > - /* Enable the UART for RX and TX; no flow ctrl */ > - pl011_write(uart, CR, RXE | TXE | UARTEN); > + /* Enable the UART for RX and TX; keep RTS and DTR */ > + cr = pl011_read(uart, CR); > + cr &= RTS | DTR; > + pl011_write(uart, CR, cr | RXE | TXE | UARTEN); > } > > static void __init pl011_init_postirq(struct serial_port *port) > diff --git a/xen/include/asm-arm/pl011-uart.h > b/xen/include/asm-arm/pl011-uart.h > index 3332c51..123f477 100644 > --- a/xen/include/asm-arm/pl011-uart.h > +++ b/xen/include/asm-arm/pl011-uart.h > @@ -38,6 +38,10 @@ > #define DMACR (0x48) > > /* CR bits */ > +#define CTSEN (1<<15) /* automatic CTS hardware flow control */ > +#define RTSEN (1<<14) /* automatic RTS hardware flow control */ > +#define RTS (1<<11) /* RTS signal */ > +#define DTR (1<<10) /* DTR signal */ > #define RXE (1<<9) /* Receive enable */ > #define TXE (1<<8) /* Transmit enable */ > #define UARTEN (1<<0) /* UART enable */ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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