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serial: pxa: work around for errata #20 

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>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Marcus Folkesson 2011-08-30 13:53:10 +02:00 committed by Greg Kroah-Hartman
parent 7d4008ebb1
commit e44aabd649
1 changed files with 20 additions and 0 deletions
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20
drivers/tty/serial/pxa.c
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@ -100,6 +100,16 @@ static inline void receive_chars(struct uart_pxa_port *up, int *status)
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 uart_pxa_port *up, int *status)
*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)