[POWERPC] spufs: Read from signal files only if data is there

We need to check the channel count of the signal notification registers
before reading them, because it can be undefined when the count is
zero. In order to read count and data atomically, we read from the
saved context.

This patch uses spu_acquire_saved() to force a context save before a
/signal1 or /signal2 read. Because of this it is no longer necessary to
have backing_ops and hw_ops versions of this function so they have been
removed.

Regular applications should not rely on reading this register
to be fast, as it's conceptually a write-only file from the PPE
perspective.

Signed-off-by: Dwayne Grant McConnell <decimal@us.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 22 insertions, 8 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index 2a2dd644101..c0cf9ee4d45 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -723,19 +723,27 @@ static ssize_t spufs_signal1_read(struct file *file, char __user *buf,
                         size_t len, loff_t *pos)
 {
         struct spu_context *ctx = file->private_data;
+        int ret = 0;
         u32 data;
 
         if (len < 4)
                 return -EINVAL;
 
-        spu_acquire(ctx);
-        data = ctx->ops->signal1_read(ctx);
+        spu_acquire_saved(ctx);
+        if (ctx->csa.spu_chnlcnt_RW[3]) {
+                data = ctx->csa.spu_chnldata_RW[3];
+                ret = 4;
+        }
         spu_release(ctx);
 
+        if (!ret)
+                goto out;
+
         if (copy_to_user(buf, &data, 4))
                 return -EFAULT;
 
-        return 4;
+out:
+        return ret;
 }
 
 static ssize_t spufs_signal1_write(struct file *file, const char __user *buf,
@@ -811,21 +819,27 @@ static int spufs_signal2_open(struct inode *inode, struct file *file)
 static ssize_t spufs_signal2_read(struct file *file, char __user *buf,
                         size_t len, loff_t *pos)
 {
-        struct spu_context *ctx;
+        struct spu_context *ctx = file->private_data;
+        int ret = 0;
         u32 data;
 
-        ctx = file->private_data;
-
         if (len < 4)
                 return -EINVAL;
 
-        spu_acquire(ctx);
-        data = ctx->ops->signal2_read(ctx);
+        spu_acquire_saved(ctx);
+        if (ctx->csa.spu_chnlcnt_RW[4]) {
+                data =  ctx->csa.spu_chnldata_RW[4];
+                ret = 4;
+        }
         spu_release(ctx);
 
+        if (!ret)
+                goto out;
+
         if (copy_to_user(buf, &data, 4))
                 return -EFAULT;
 
+out:
         return 4;
 }