| Date | Wed, 09 Nov 2011 13:31:01 -0800 | From | Greg KH <> | Subject | [014/264] serial: pxa: work around for errata #20 |
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3.1-stable review patch. If anyone has any objections, please let me know.
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From: Marcus Folkesson <marcus.folkesson@gmail.com>
commit e44aabd649c80e8be16ede3ed3cbff6fb2561ca9 upstream.
Errata E20: UART: Character Timeout interrupt remains set under certain software conditions.
Implication: The software servicing the UART can be trapped in an infinite loop.
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/tty/serial/pxa.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
--- a/drivers/tty/serial/pxa.c +++ b/drivers/tty/serial/pxa.c @@ -100,6 +100,16 @@ static inline void receive_chars(struct int max_count = 256; do { + /* work around Errata #20 according to + * Intel(R) PXA27x Processor Family + * Specification Update (May 2005) + * + * Step 2 + * Disable the Reciever Time Out Interrupt via IER[RTOEI] + */ + up->ier &= ~UART_IER_RTOIE; + serial_out(up, UART_IER, up->ier); + ch = serial_in(up, UART_RX); flag = TTY_NORMAL; up->port.icount.rx++; @@ -156,6 +166,16 @@ static inline void receive_chars(struct *status = serial_in(up, UART_LSR); } while ((*status & UART_LSR_DR) && (max_count-- > 0)); tty_flip_buffer_push(tty); + + /* work around Errata #20 according to + * Intel(R) PXA27x Processor Family + * Specification Update (May 2005) + * + * Step 6: + * No more data in FIFO: Re-enable RTO interrupt via IER[RTOIE] + */ + up->ier |= UART_IER_RTOIE; + serial_out(up, UART_IER, up->ier); } static void transmit_chars(struct uart_pxa_port *up)
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