serial: amba-pl011: preseserve hardware settings during initialisation
During initialisation, a UART may already be in use for a console, so
take care to preserve things like baud rate and data format to avoid
corrupting console output.
Signed-off-by: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 844bfba9..182a922 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1529,7 +1529,7 @@
static int pl011_startup(struct uart_port *port)
{
struct uart_amba_port *uap = (struct uart_amba_port *)port;
- unsigned int cr;
+ unsigned int cr, lcr_h, fbrd, ibrd;
int retval;
retval = pl011_hwinit(port);
@@ -1548,10 +1548,16 @@
writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS);
/*
- * Provoke TX FIFO interrupt into asserting.
+ * Provoke TX FIFO interrupt into asserting. Taking care to preserve
+ * baud rate and data format specified by FBRD, IBRD and LCRH as the
+ * UART may already be in use as a console.
*/
spin_lock_irq(&uap->port.lock);
+ fbrd = readw(uap->port.membase + UART011_FBRD);
+ ibrd = readw(uap->port.membase + UART011_IBRD);
+ lcr_h = readw(uap->port.membase + uap->lcrh_rx);
+
cr = UART01x_CR_UARTEN | UART011_CR_TXE | UART011_CR_LBE;
writew(cr, uap->port.membase + UART011_CR);
writew(0, uap->port.membase + UART011_FBRD);
@@ -1561,6 +1567,10 @@
while (readw(uap->port.membase + UART01x_FR) & UART01x_FR_BUSY)
barrier();
+ writew(fbrd, uap->port.membase + UART011_FBRD);
+ writew(ibrd, uap->port.membase + UART011_IBRD);
+ pl011_write_lcr_h(uap, lcr_h);
+
/* restore RTS and DTR */
cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);
cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;