MIPS: DB1200: Set Config[OD] for improved stability.

Setting Config[OD] gets rid of a _LOT_ of spurious CPLD interrupts,
but also decreases overall performance a bit.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Patchwork: https://patchwork.linux-mips.org/patch/2347/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/alchemy/common/setup.c

@@ -52,15 +52,15 @@ void __init plat_mem_setup(void)
 	/* this is faster than wasting cycles trying to approximate it */
 	preset_lpj = (est_freq >> 1) / HZ;
 
-	board_setup();  /* board specific setup */
-
 	if (au1xxx_cpu_needs_config_od())
 		/* Various early Au1xx0 errata corrected by this */
 		set_c0_config(1 << 19); /* Set Config[OD] */
 	else
 		/* Clear to obtain best system bus performance */
 		clear_c0_config(1 << 19); /* Clear Config[OD] */
 
+	board_setup();  /* board specific setup */
+
 	/* IO/MEM resources. */
 	set_io_port_base(0);
 	ioport_resource.start = IOPORT_RESOURCE_START;

arch/mips/alchemy/devboards/db1200/setup.c

@@ -23,6 +23,13 @@ void __init board_setup(void)
 	unsigned long freq0, clksrc, div, pfc;
 	unsigned short whoami;
 
+	/* Set Config[OD] (disable overlapping bus transaction):
+	 * This gets rid of a _lot_ of spurious interrupts (especially
+	 * wrt. IDE); but incurs ~10% performance hit in some
+	 * cpu-bound applications.
+	 */
+	set_c0_config(1 << 19);
+
 	bcsr_init(DB1200_BCSR_PHYS_ADDR,
 		  DB1200_BCSR_PHYS_ADDR + DB1200_BCSR_HEXLED_OFS);