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authorJon Medhurst <tixy@linaro.org>2013-12-10 11:19:00 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-17 18:35:38 +0100
commit570d291048aecc02271884f6a5f50ad555f271a5 (patch)
tree9d9e47b193b44c5550cbdd24b93a687d3a8b6d56 /drivers/tty/serial/amba-pl011.c
parentserial: amba-pl011: factor out code for writing LCR_H register (diff)
downloadlinux-570d291048aecc02271884f6a5f50ad555f271a5.tar.xz
linux-570d291048aecc02271884f6a5f50ad555f271a5.zip
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>
Diffstat (limited to 'drivers/tty/serial/amba-pl011.c')
-rw-r--r--drivers/tty/serial/amba-pl011.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 844bfba9d0ab..182a922e1942 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1529,7 +1529,7 @@ static void pl011_write_lcr_h(struct uart_amba_port *uap, unsigned int lcr_h)
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 @@ static int pl011_startup(struct uart_port *port)
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 @@ static int pl011_startup(struct uart_port *port)
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;