Ralf Baechle wrote: > 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 <jan.nikitenko@xxxxxxxxx> > > Fairly unelegent imho but anyway, for 2.6.24 I've added support for > tickless to MIPS which in turn required a bit of a cleanup on the Alchemy > code so I renumbered the Alchemy interrupt numbers, so what used to be > IRQ 0 is now IRQ 8 which means your patch is no longer needed for master. That's good to know. > > That said, irq 0 is imho totally valid (take the good old PIT timer > interrupt of the PC as the classic example) and treating it as an invalid > interrupt number is broken. > > It's however equally pretty crude hack to undefine a symbol in a file other > than the one defining it ... I did exactly as the comment in 8250.c suggested (that arch include could redefine that macro) - I did not like it either... Jan
