[PATCH] spufs: fix mailbox polling

Handling mailbox interrupts was broken in multiple respects,
the combination of which was hiding the bugs most of the time.

- The ibox interrupt mask was open initially even though there
  are no waiters on a newly created SPU.

- Acknowledging the mailbox interrupt did not work because
  it is level triggered and the mailbox data is never retrieved
  from inside the interrupt handler.

- The interrupt handler delivered interrupts with a disabled
  mask if another interrupt is triggered for the same class
  but a different mask.

- The poll function did not enable the interrupt if it had not
  been enabled, so we might run into the poll timeout if none of
  the other bugs saved us and no signal was delivered.

We probably still have a similar problem with blocking
read/write on mailbox files, but that will result in extra
wakeup in the worst case, not in incorrect behaviour.

Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 40 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/hw_ops.c b/arch/powerpc/platforms/cell/spufs/hw_ops.c
index 68812415ee29..9a53e29f9d7e 100644
--- a/arch/powerpc/platforms/cell/spufs/hw_ops.c
+++ b/arch/powerpc/platforms/cell/spufs/hw_ops.c
@@ -24,7 +24,7 @@
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
-#include <linux/vmalloc.h>
+#include <linux/poll.h>
 #include <linux/smp.h>
 #include <linux/smp_lock.h>
 #include <linux/stddef.h>
@@ -58,6 +58,44 @@ static u32 spu_hw_mbox_stat_read(struct spu_context *ctx)
 	return in_be32(&ctx->spu->problem->mb_stat_R);
 }
 
+static unsigned int spu_hw_mbox_stat_poll(struct spu_context *ctx,
+					  unsigned int events)
+{
+	struct spu *spu = ctx->spu;
+	struct spu_priv1 __iomem *priv1 = spu->priv1;
+	int ret = 0;
+	u32 stat;
+
+	spin_lock_irq(&spu->register_lock);
+	stat = in_be32(&spu->problem->mb_stat_R);
+
+	/* if the requested event is there, return the poll
+	   mask, otherwise enable the interrupt to get notified,
+	   but first mark any pending interrupts as done so
+	   we don't get woken up unnecessarily */
+
+	if (events & (POLLIN | POLLRDNORM)) {
+		if (stat & 0xff0000)
+			ret |= POLLIN | POLLRDNORM;
+		else {
+			out_be64(&priv1->int_stat_class2_RW, 0x1);
+			out_be64(&priv1->int_mask_class2_RW,
+				 in_be64(&priv1->int_mask_class2_RW) | 0x1);
+		}
+	}
+	if (events & (POLLOUT | POLLWRNORM)) {
+		if (stat & 0x00ff00)
+			ret = POLLOUT | POLLWRNORM;
+		else {
+			out_be64(&priv1->int_stat_class2_RW, 0x10);
+			out_be64(&priv1->int_mask_class2_RW,
+				 in_be64(&priv1->int_mask_class2_RW) | 0x10);
+		}
+	}
+	spin_unlock_irq(&spu->register_lock);
+	return ret;
+}
+
 static int spu_hw_ibox_read(struct spu_context *ctx, u32 * data)
 {
 	struct spu *spu = ctx->spu;
@@ -204,6 +242,7 @@ static void spu_hw_runcntl_stop(struct spu_context *ctx)
 struct spu_context_ops spu_hw_ops = {
 	.mbox_read = spu_hw_mbox_read,
 	.mbox_stat_read = spu_hw_mbox_stat_read,
+	.mbox_stat_poll = spu_hw_mbox_stat_poll,
 	.ibox_read = spu_hw_ibox_read,
 	.wbox_write = spu_hw_wbox_write,
 	.signal1_read = spu_hw_signal1_read,