[PATCH] ppc32: Bump PMU interrupt priority

The Power Management Unit on PowerMacs is very sensitive to timeouts during
async message exchanges.  It uses rather crude protocol based on a shift
register with an interrupt and is almost continuously exchanging messages with
the host CPU on laptops.

This patch adds a routine to the open_pic driver to be able to select a PMU
driver so that it bumps it's interrupt priority to above the normal level.

This will allow PMU interrupts to occur while another interrupt is pending,
and thus reduce the risk of machine beeing abruptly shutdown by the PMU due to
a timeout in PMU communication caused by excessive interrupt latency.  The
problem is very rare, and usually just doesn't happen, but it is still useful
to make things even more robust.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 19 insertions, 7 deletions

diff --git a/arch/ppc/syslib/open_pic.c b/arch/ppc/syslib/open_pic.c
index b45d8268bf93..ad39b86ca92c 100644
--- a/arch/ppc/syslib/open_pic.c
+++ b/arch/ppc/syslib/open_pic.c
@@ -370,8 +370,9 @@ void __init openpic_init(int offset)
         /* Initialize IPI interrupts */
         if ( ppc_md.progress ) ppc_md.progress("openpic: ipi",0x3bb);
         for (i = 0; i < OPENPIC_NUM_IPI; i++) {
-                /* Disabled, Priority 10..13 */
-                openpic_initipi(i, 10+i, OPENPIC_VEC_IPI+i+offset);
+                /* Disabled, increased priorities 10..13 */
+                openpic_initipi(i, OPENPIC_PRIORITY_IPI_BASE+i,
+                                OPENPIC_VEC_IPI+i+offset);
                 /* IPIs are per-CPU */
                 irq_desc[OPENPIC_VEC_IPI+i+offset].status |= IRQ_PER_CPU;
                 irq_desc[OPENPIC_VEC_IPI+i+offset].handler = &open_pic_ipi;
@@ -399,8 +400,9 @@ void __init openpic_init(int offset)
                 if (sense & IRQ_SENSE_MASK)
                         irq_desc[i+offset].status = IRQ_LEVEL;
 
-                /* Enabled, Priority 8 */
-                openpic_initirq(i, 8, i+offset, (sense & IRQ_POLARITY_MASK),
+                /* Enabled, Default priority */
+                openpic_initirq(i, OPENPIC_PRIORITY_DEFAULT, i+offset,
+                                (sense & IRQ_POLARITY_MASK),
                                 (sense & IRQ_SENSE_MASK));
                 /* Processor 0 */
                 openpic_mapirq(i, CPU_MASK_CPU0, CPU_MASK_NONE);
@@ -656,6 +658,18 @@ static void __init openpic_maptimer(u_int timer, cpumask_t cpumask)
 }
 
 /*
+ * Change the priority of an interrupt
+ */
+void __init
+openpic_set_irq_priority(u_int irq, u_int pri)
+{
+        check_arg_irq(irq);
+        openpic_safe_writefield(&ISR[irq - open_pic_irq_offset]->Vector_Priority,
+                                OPENPIC_PRIORITY_MASK,
+                                pri << OPENPIC_PRIORITY_SHIFT);
+}
+
+/*
  * Initalize the interrupt source which will generate an NMI.
  * This raises the interrupt's priority from 8 to 9.
  *
@@ -665,9 +679,7 @@ void __init
 openpic_init_nmi_irq(u_int irq)
 {
         check_arg_irq(irq);
-        openpic_safe_writefield(&ISR[irq - open_pic_irq_offset]->Vector_Priority,
-                                OPENPIC_PRIORITY_MASK,
-                                9 << OPENPIC_PRIORITY_SHIFT);
+        openpic_set_irq_priority(irq, OPENPIC_PRIORITY_NMI);
 }
 
 /*