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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>
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570d291048
1 changed files with 12 additions and 2 deletions
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@ -1529,7 +1529,7 @@ static void pl011_write_lcr_h(struct uart_amba_port *uap, unsigned int lcr_h)
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static int pl011_startup(struct uart_port *port)
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{
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struct uart_amba_port *uap = (struct uart_amba_port *)port;
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unsigned int cr;
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unsigned int cr, lcr_h, fbrd, ibrd;
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int retval;
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retval = pl011_hwinit(port);
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@ -1548,10 +1548,16 @@ static int pl011_startup(struct uart_port *port)
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writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS);
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/*
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* Provoke TX FIFO interrupt into asserting.
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* Provoke TX FIFO interrupt into asserting. Taking care to preserve
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* baud rate and data format specified by FBRD, IBRD and LCRH as the
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* UART may already be in use as a console.
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*/
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spin_lock_irq(&uap->port.lock);
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fbrd = readw(uap->port.membase + UART011_FBRD);
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ibrd = readw(uap->port.membase + UART011_IBRD);
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lcr_h = readw(uap->port.membase + uap->lcrh_rx);
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cr = UART01x_CR_UARTEN | UART011_CR_TXE | UART011_CR_LBE;
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writew(cr, uap->port.membase + UART011_CR);
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writew(0, uap->port.membase + UART011_FBRD);
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@ -1561,6 +1567,10 @@ static int pl011_startup(struct uart_port *port)
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while (readw(uap->port.membase + UART01x_FR) & UART01x_FR_BUSY)
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barrier();
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writew(fbrd, uap->port.membase + UART011_FBRD);
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writew(ibrd, uap->port.membase + UART011_IBRD);
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pl011_write_lcr_h(uap, lcr_h);
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/* restore RTS and DTR */
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cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);
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cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
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