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serial: amba-pl011: preseserve hardware settings during initialisation

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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>
This commit is contained in:
Jon Medhurst 2013-12-10 10:19:00 +00:00 committed by Greg Kroah-Hartman
parent b60f2f66a5
commit 570d291048
1 changed files with 12 additions and 2 deletions
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14
drivers/tty/serial/amba-pl011.c
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@ -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;