[POWERPC] cell: Fix lost interrupts due to fasteoi handler

We may currently lose interrupts during SPE context switch, as we alter
the INT_Route register. Because the IIC uses a per-thread priority
status, changing the interrupt routing to a different thread means that
the IRQ is no longer masked by the priority status, so we end up with
two fasteoi IRQ handlers executing for the one irq_desc. The fasteoi
handler doesn't handle multiple IRQs, so drops the second one.

Fix this by using our own flow handler. This is based on
handle_edge_irq, but issues an eoi after IRQs are handled, and doesn't
do any mask/unmasking.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

1 files changed, 51 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/cell/interrupt.c b/arch/powerpc/platforms/cell/interrupt.c
index 04f74f9f9ab6..5bf7df146022 100644
--- a/arch/powerpc/platforms/cell/interrupt.c
+++ b/arch/powerpc/platforms/cell/interrupt.c
@@ -35,6 +35,7 @@
 #include <linux/percpu.h>
 #include <linux/types.h>
 #include <linux/ioport.h>
+#include <linux/kernel_stat.h>
 
 #include <asm/io.h>
 #include <asm/pgtable.h>
@@ -231,6 +232,54 @@ static int iic_host_match(struct irq_host *h, struct device_node *node)
                                     "IBM,CBEA-Internal-Interrupt-Controller");
 }
 
+extern int noirqdebug;
+
+static void handle_iic_irq(unsigned int irq, struct irq_desc *desc)
+{
+        const unsigned int cpu = smp_processor_id();
+
+        spin_lock(&desc->lock);
+
+        desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
+
+        /*
+         * If we're currently running this IRQ, or its disabled,
+         * we shouldn't process the IRQ. Mark it pending, handle
+         * the necessary masking and go out
+         */
+        if (unlikely((desc->status & (IRQ_INPROGRESS | IRQ_DISABLED)) ||
+                    !desc->action)) {
+                desc->status |= IRQ_PENDING;
+                goto out_eoi;
+        }
+
+        kstat_cpu(cpu).irqs[irq]++;
+
+        /* Mark the IRQ currently in progress.*/
+        desc->status |= IRQ_INPROGRESS;
+
+        do {
+                struct irqaction *action = desc->action;
+                irqreturn_t action_ret;
+
+                if (unlikely(!action))
+                        goto out_eoi;
+
+                desc->status &= ~IRQ_PENDING;
+                spin_unlock(&desc->lock);
+                action_ret = handle_IRQ_event(irq, action);
+                if (!noirqdebug)
+                        note_interrupt(irq, desc, action_ret);
+                spin_lock(&desc->lock);
+
+        } while ((desc->status & (IRQ_PENDING | IRQ_DISABLED)) == IRQ_PENDING);
+
+        desc->status &= ~IRQ_INPROGRESS;
+out_eoi:
+        desc->chip->eoi(irq);
+        spin_unlock(&desc->lock);
+}
+
 static int iic_host_map(struct irq_host *h, unsigned int virq,
                         irq_hw_number_t hw)
 {
@@ -240,10 +289,10 @@ static int iic_host_map(struct irq_host *h, unsigned int virq,
                 break;
         case IIC_IRQ_TYPE_IOEXC:
                 set_irq_chip_and_handler(virq, &iic_ioexc_chip,
-                                         handle_fasteoi_irq);
+                                         handle_iic_irq);
                 break;
         default:
-                set_irq_chip_and_handler(virq, &iic_chip, handle_fasteoi_irq);
+                set_irq_chip_and_handler(virq, &iic_chip, handle_iic_irq);
         }
         return 0;
 }