ARM: OMAP3: PM: fix shared PRCM interrupts: leave disabled at boot

By default, request_irq() will auto-enable the requested IRQ.

For PRCM interrupts, we may want to avoid that until the PM core code
is fully ready to handle the interrupts.  This is particularily true
for IO pad interrupts on OMAP3, which are shared between the hwmod
core and the PRM core.

In order to avoid PRCM IO-chain interrupts until the PM core is ready
to handle them, ready, set the IRQ_NOAUTOEN flag for the PRCM IO-chain
interrupt,  which means it will remain disabled after request_irq().

Then, explicitly enable the PRCM interrupts after the request_irq() in
the PM core (but not in the hwmod core.)

Special thanks to Tero Kristo for suggesting to isolate the fix to
only the IO-chain interrupt on OMAP3 instead of all PRCM interrupts.

Cc: Tero Kristo <t-kristo@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/pm34xx.c

@@ -729,6 +729,7 @@ static int __init omap3_pm_init(void)
 	ret = request_irq(omap_prcm_event_to_irq("io"),
 		_prcm_int_handle_io, IRQF_SHARED | IRQF_NO_SUSPEND, "pm_io",
 		omap3_pm_init);
+	enable_irq(omap_prcm_event_to_irq("io"));
 
 	if (ret) {
 		pr_err("pm: Failed to request pm_io irq\n");

arch/arm/mach-omap2/prm2xxx_3xxx.c

@@ -15,6 +15,7 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/io.h>
+#include <linux/irq.h>
 
 #include "common.h"
 #include <plat/cpu.h>
@@ -303,8 +304,15 @@ void omap3xxx_prm_restore_irqen(u32 *saved_mask)
 
 static int __init omap3xxx_prcm_init(void)
 {
-	if (cpu_is_omap34xx())
-		return omap_prcm_register_chain_handler(&omap3_prcm_irq_setup);
-	return 0;
+	int ret = 0;
+
+	if (cpu_is_omap34xx()) {
+		ret = omap_prcm_register_chain_handler(&omap3_prcm_irq_setup);
+		if (!ret)
+			irq_set_status_flags(omap_prcm_event_to_irq("io"),
+					     IRQ_NOAUTOEN);
+	}
+
+	return ret;
 }
 subsys_initcall(omap3xxx_prcm_init);