[PATCH] PPC4xx UART0 (8250) problem

[Mikhail Zolotaryov <lebon@faust.net.ua>]

On PPC4xx embedded we often have UART0 on IRQ0 but 8250 UART driver uses
IRQ0 as "no irq" hack.
It's suggested that platforms with UART on IRQ0 will redefine
is_real_interrupt(irq) macro but 8250 code anyway overrides that.
As the result, serial line on UART0 works on polling-way and we have
character loss on high baud rates.

In patch I've added check if UART0 is on IRQ0, if so we define
is_real_interrupt macro to be 1 (true).
Also, check if is_real_interrupt macro is already defined added to 8250
UART driver.

--- linux-2.6.20.5.orig/include/asm-ppc/ibm4xx.h        2007-03-23
21:52:51.000000000 +0200
+++ linux-2.6.20.5/include/asm-ppc/ibm4xx.h     2007-04-06
17:37:22.000000000 +0300
@@ -54,6 +54,12 @@
 #include <platforms/4xx/xilinx_ml403.h>
 #endif
 
+#ifdef UART0_INT
+#if (UART0_INT == 0)
+#define is_real_interrupt(irq)  (1)
+#endif
+#endif
+
 #ifndef __ASSEMBLY__
 
 #ifdef CONFIG_40x
--- linux-2.6.20.5.orig/drivers/serial/8250.c   2007-03-23
21:52:51.000000000 +0200
+++ linux-2.6.20.5/drivers/serial/8250.c        2007-04-06
16:44:32.000000000 +0300
@@ -77,7 +77,10 @@
  * machine types want others as well - they're free
  * to redefine this in their header file.
  */
+
+#ifndef is_real_interrupt(irq)
 #define is_real_interrupt(irq) ((irq) != 0)
+#endif
 
 #ifdef CONFIG_SERIAL_8250_DETECT_IRQ
 #define CONFIG_SERIAL_DETECT_IRQ 1

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