1 files changed, 19 insertions, 10 deletions

diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index 3d2c6baae96b..233bd87a9637 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -324,17 +324,25 @@ static void sun4u_set_affinity(unsigned int virt_irq,
         sun4u_irq_enable(virt_irq);
 }
 
+/* Don't do anything.  The desc->status check for IRQ_DISABLED in
+ * handler_irq() will skip the handler call and that will leave the
+ * interrupt in the sent state.  The next ->enable() call will hit the
+ * ICLR register to reset the state machine.
+ *
+ * This scheme is necessary, instead of clearing the Valid bit in the
+ * IMAP register, to handle the case of IMAP registers being shared by
+ * multiple INOs (and thus ICLR registers).  Since we use a different
+ * virtual IRQ for each shared IMAP instance, the generic code thinks
+ * there is only one user so it prematurely calls ->disable() on
+ * free_irq().
+ *
+ * We have to provide an explicit ->disable() method instead of using
+ * NULL to get the default.  The reason is that if the generic code
+ * sees that, it also hooks up a default ->shutdown method which
+ * invokes ->mask() which we do not want.  See irq_chip_set_defaults().
+ */
 static void sun4u_irq_disable(unsigned int virt_irq)
 {
-        struct irq_handler_data *data = get_irq_chip_data(virt_irq);
-
-        if (likely(data)) {
-                unsigned long imap = data->imap;
-                unsigned long tmp = upa_readq(imap);
-
-                tmp &= ~IMAP_VALID;
-                upa_writeq(tmp, imap);
-        }
 }
 
 static void sun4u_irq_eoi(unsigned int virt_irq)
@@ -747,7 +755,8 @@ void handler_irq(int irq, struct pt_regs *regs)
 
                 desc = irq_desc + virt_irq;
 
-                desc->handle_irq(virt_irq, desc);
+                if (!(desc->status & IRQ_DISABLED))
+                        desc->handle_irq(virt_irq, desc);
 
                 bucket_pa = next_pa;
         }