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Re: [PATCH] serial: fix au1xxx UART0 irq setup

To: Jan Nikitenko <>
Subject: Re: [PATCH] serial: fix au1xxx UART0 irq setup
From: Ralf Baechle <>
Date: Mon, 29 Oct 2007 15:28:25 +0000
In-reply-to: <>
Original-recipient: rfc822;
References: <>
User-agent: Mutt/1.5.14 (2007-02-12)
On Thu, Oct 25, 2007 at 03:58:54PM +0200, Jan Nikitenko wrote:

> UART0 on Alchemy mips platforms (au1xxx) does not use real uart's hw
> irq, causing 'ttyS0: 1 input overrun(s)' kernel message with data loss,
> when more characters than uart's fifo size were to be received by the uart.
> This problem can be experienced for example when uart0 is used as a
> serial console on au1550 and more than 16 characters are pasted from
> clipboard to the console.
> The is_real_interrupt(irq) macro is defined in drivers/serial/8250.c as
> a check, if the irq number is other than zero.
> Because UART0 on au1xxx platforms uses irq number 0, the
> is_real_interrupt() check fails and serial8250_backup_timeout() is used
> instead of uart's hw irq.
> The patch redefines the is_real_interrupt(irq) macro, as suggested in
> the comment above the macro definition in 8250.c, in the
> asm-mips/serial.h to be always true for CONFIG_SERIAL_8250_AU1X00.
> This allows the irq number 0 to be used as hw irq for the alchemy uart0
> and fixes the overrun problem.
> Signed-off-by: Jan Nikitenko <>

So applied to all of lmo's -stable branches.


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