sh: intc - primary priority masking fixes

This patch contains various intc fixes for problems reported by
Markus Brunner on the linuxsh-dev mailing list:

http://marc.info/?l=linuxsh-dev&m=118701948224991&w=1

Apart from added comments, the fixes are:

- add intc_set_priority() function prototype to hw_irq.h
- fix off-by-one error in intc_set_priority()
- make sure _INTC_WIDTH() is set for primary priority masking

Big thanks to Markus for finding these problems. Version two fixes
a compile error and an inverted primary check.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: Markus Brunner <super.firetwister@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 28 insertions, 5 deletions

diff --git a/arch/sh/kernel/cpu/irq/intc.c b/arch/sh/kernel/cpu/irq/intc.c
index d609a8ccd456..481871fee1a8 100644
--- a/arch/sh/kernel/cpu/irq/intc.c
+++ b/arch/sh/kernel/cpu/irq/intc.c
@@ -206,6 +206,18 @@ static struct intc_handle_int *intc_find_irq(struct intc_handle_int *hp,
 {
         int i;
 
+        /* this doesn't scale well, but...
+         *
+         * this function should only be used for cerain uncommon
+         * operations such as intc_set_priority() and intc_set_sense()
+         * and in those rare cases performance doesn't matter that much.
+         * keeping the memory footprint low is more important.
+         *
+         * one rather simple way to speed this up and still keep the
+         * memory footprint down is to make sure the array is sorted
+         * and then perform a bisect to lookup the irq.
+         */
+
         for (i = 0; i < nr_hp; i++) {
                 if ((hp + i)->irq != irq)
                         continue;
@@ -226,7 +238,7 @@ int intc_set_priority(unsigned int irq, unsigned int prio)
 
         ihp = intc_find_irq(d->prio, d->nr_prio, irq);
         if (ihp) {
-                if (prio >= ((1 << _INTC_WIDTH(ihp->handle)) - 1))
+                if (prio >= (1 << _INTC_WIDTH(ihp->handle)))
                         return -EINVAL;
 
                 intc_prio_level[irq] = prio;
@@ -237,7 +249,7 @@ int intc_set_priority(unsigned int irq, unsigned int prio)
                  * priority level will be set during next enable()
                  */
 
-                if (ihp->handle)
+                if (_INTC_FN(ihp->handle) != REG_FN_ERR)
                         _intc_enable(irq, ihp->handle);
         }
         return 0;
@@ -457,6 +469,7 @@ static void __init intc_register_irq(struct intc_desc *desc,
                                      intc_enum enum_id,
                                      unsigned int irq)
 {
+        struct intc_handle_int *hp;
         unsigned int data[2], primary;
 
         /* Prefer single interrupt source bitmap over other combinations:
@@ -495,9 +508,19 @@ static void __init intc_register_irq(struct intc_desc *desc,
 
         /* add irq to d->prio list if priority is available */
         if (data[1]) {
-                (d->prio + d->nr_prio)->irq = irq;
-                if (!primary) /* only secondary priority can access regs */
-                        (d->prio + d->nr_prio)->handle = data[1];
+                hp = d->prio + d->nr_prio;
+                hp->irq = irq;
+                hp->handle = data[1];
+
+                if (primary) {
+                        /*
+                         * only secondary priority should access registers, so
+                         * set _INTC_FN(h) = REG_FN_ERR for intc_set_priority()
+                         */
+
+                        hp->handle &= ~_INTC_MK(0x0f, 0, 0, 0, 0, 0);
+                        hp->handle |= _INTC_MK(REG_FN_ERR, 0, 0, 0, 0, 0);
+                }
                 d->nr_prio++;
         }