[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>

arch/powerpc/platforms/cell/spu_base.c

@@ -202,12 +202,15 @@ spu_irq_class_0(int irq, void *data, struct pt_regs *regs)
 int
 spu_irq_class_0_bottom(struct spu *spu)
 {
-	unsigned long stat;
+	unsigned long stat, mask;
 
 	spu->class_0_pending = 0;
 
+	mask = in_be64(&spu->priv1->int_mask_class0_RW);
 	stat = in_be64(&spu->priv1->int_stat_class0_RW);
 
+	stat &= mask;
+
 	if (stat & 1) /* invalid MFC DMA */
 		__spu_trap_invalid_dma(spu);
 
@@ -263,13 +266,15 @@ spu_irq_class_2(int irq, void *data, struct pt_regs *regs)
 {
 	struct spu *spu;
 	unsigned long stat;
+	unsigned long mask;
 
 	spu = data;
 	stat = in_be64(&spu->priv1->int_stat_class2_RW);
+	mask = in_be64(&spu->priv1->int_mask_class2_RW);
 
-	pr_debug("class 2 interrupt %d, %lx, %lx\n", irq, stat,
-		in_be64(&spu->priv1->int_mask_class2_RW));
+	pr_debug("class 2 interrupt %d, %lx, %lx\n", irq, stat, mask);
 
+	stat &= mask;
 
 	if (stat & 1)  /* PPC core mailbox */
 		__spu_trap_mailbox(spu);

arch/powerpc/platforms/cell/spufs/backing_ops.c

@@ -32,6 +32,7 @@
 #include <linux/smp_lock.h>
 #include <linux/stddef.h>
 #include <linux/unistd.h>
+#include <linux/poll.h>
 
 #include <asm/io.h>
 #include <asm/spu.h>
@@ -87,6 +88,41 @@ static u32 spu_backing_mbox_stat_read(struct spu_context *ctx)
 	return ctx->csa.prob.mb_stat_R;
 }
 
+static unsigned int spu_backing_mbox_stat_poll(struct spu_context *ctx,
+					  unsigned int events)
+{
+	int ret;
+	u32 stat;
+
+	ret = 0;
+	spin_lock_irq(&ctx->csa.register_lock);
+	stat = ctx->csa.prob.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 {
+			ctx->csa.priv1.int_stat_class0_RW &= ~0x1;
+			ctx->csa.priv1.int_mask_class2_RW |= 0x1;
+		}
+	}
+	if (events & (POLLOUT | POLLWRNORM)) {
+		if (stat & 0x00ff00)
+			ret = POLLOUT | POLLWRNORM;
+		else {
+			ctx->csa.priv1.int_stat_class0_RW &= ~0x10;
+			ctx->csa.priv1.int_mask_class2_RW |= 0x10;
+		}
+	}
+	spin_unlock_irq(&ctx->csa.register_lock);
+	return ret;
+}
+
 static int spu_backing_ibox_read(struct spu_context *ctx, u32 * data)
 {
 	int ret;
@@ -252,6 +288,7 @@ static void spu_backing_runcntl_stop(struct spu_context *ctx)
 struct spu_context_ops spu_backing_ops = {
 	.mbox_read = spu_backing_mbox_read,
 	.mbox_stat_read = spu_backing_mbox_stat_read,
+	.mbox_stat_poll = spu_backing_mbox_stat_poll,
 	.ibox_read = spu_backing_ibox_read,
 	.wbox_write = spu_backing_wbox_write,
 	.signal1_read = spu_backing_signal1_read,

arch/powerpc/platforms/cell/spufs/file.c

@@ -389,20 +389,13 @@ static ssize_t spufs_ibox_read(struct file *file, char __user *buf,
 static unsigned int spufs_ibox_poll(struct file *file, poll_table *wait)
 {
 	struct spu_context *ctx = file->private_data;
-	u32 mbox_stat;
 	unsigned int mask;
 
-	spu_acquire(ctx);
-
-	mbox_stat = ctx->ops->mbox_stat_read(ctx);
-
-	spu_release(ctx);
-
 	poll_wait(file, &ctx->ibox_wq, wait);
 
-	mask = 0;
-	if (mbox_stat & 0xff0000)
-		mask |= POLLIN | POLLRDNORM;
+	spu_acquire(ctx);
+	mask = ctx->ops->mbox_stat_poll(ctx, POLLIN | POLLRDNORM);
+	spu_release(ctx);
 
 	return mask;
 }
@@ -494,18 +487,13 @@ static ssize_t spufs_wbox_write(struct file *file, const char __user *buf,
 static unsigned int spufs_wbox_poll(struct file *file, poll_table *wait)
 {
 	struct spu_context *ctx = file->private_data;
-	u32 mbox_stat;
 	unsigned int mask;
 
-	spu_acquire(ctx);
-	mbox_stat = ctx->ops->mbox_stat_read(ctx);
-	spu_release(ctx);
-
 	poll_wait(file, &ctx->wbox_wq, wait);
 
-	mask = 0;
-	if (mbox_stat & 0x00ff00)
-		mask = POLLOUT | POLLWRNORM;
+	spu_acquire(ctx);
+	mask = ctx->ops->mbox_stat_poll(ctx, POLLOUT | POLLWRNORM);
+	spu_release(ctx);
 
 	return mask;
 }

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,

arch/powerpc/platforms/cell/spufs/spufs.h

@@ -66,6 +66,8 @@ struct spu_context {
 struct spu_context_ops {
 	int (*mbox_read) (struct spu_context * ctx, u32 * data);
 	 u32(*mbox_stat_read) (struct spu_context * ctx);
+	unsigned int (*mbox_stat_poll)(struct spu_context *ctx,
+					unsigned int events);
 	int (*ibox_read) (struct spu_context * ctx, u32 * data);
 	int (*wbox_write) (struct spu_context * ctx, u32 data);
 	 u32(*signal1_read) (struct spu_context * ctx);

arch/powerpc/platforms/cell/spufs/switch.c

@@ -2155,8 +2155,8 @@ static void init_priv1(struct spu_state *csa)
 	    CLASS0_ENABLE_SPU_ERROR_INTR;
 	csa->priv1.int_mask_class1_RW = CLASS1_ENABLE_SEGMENT_FAULT_INTR |
 	    CLASS1_ENABLE_STORAGE_FAULT_INTR;
-	csa->priv1.int_mask_class2_RW = CLASS2_ENABLE_MAILBOX_INTR |
-	    CLASS2_ENABLE_SPU_STOP_INTR | CLASS2_ENABLE_SPU_HALT_INTR;
+	csa->priv1.int_mask_class2_RW = CLASS2_ENABLE_SPU_STOP_INTR |
+	    CLASS2_ENABLE_SPU_HALT_INTR;
 }
 
 static void init_priv2(struct spu_state *csa)