ALSA: ca0106 - clean up playback pointer callback

Clean up the playback pointer callback function a bit, and make the
pointer check more strictly to avoid bogus pointers.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 16 insertions, 18 deletions

diff --git a/sound/pci/ca0106/ca0106_main.c b/sound/pci/ca0106/ca0106_main.c
index 0a3d3d6e77b..8e69620da20 100644
--- a/sound/pci/ca0106/ca0106_main.c
+++ b/sound/pci/ca0106/ca0106_main.c
@@ -1002,29 +1002,27 @@ snd_ca0106_pcm_pointer_playback(struct snd_pcm_substream *substream)
         struct snd_ca0106 *emu = snd_pcm_substream_chip(substream);
         struct snd_pcm_runtime *runtime = substream->runtime;
         struct snd_ca0106_pcm *epcm = runtime->private_data;
-        snd_pcm_uframes_t ptr, ptr1, ptr2,ptr3,ptr4 = 0;
+        unsigned int ptr, prev_ptr;
         int channel = epcm->channel_id;
+        int timeout = 10;
 
         if (!epcm->running)
                 return 0;
 
-        ptr3 = snd_ca0106_ptr_read(emu, PLAYBACK_LIST_PTR, channel);
-        ptr1 = snd_ca0106_ptr_read(emu, PLAYBACK_POINTER, channel);
-        ptr4 = snd_ca0106_ptr_read(emu, PLAYBACK_LIST_PTR, channel);
-        if (ptr3 != ptr4) ptr1 = snd_ca0106_ptr_read(emu, PLAYBACK_POINTER, channel);
-        ptr2 = bytes_to_frames(runtime, ptr1);
-        ptr2+= (ptr4 >> 3) * runtime->period_size;
-        ptr=ptr2;
-        if (ptr >= runtime->buffer_size)
-                ptr -= runtime->buffer_size;
-        /*
-        printk(KERN_DEBUG "ptr1 = 0x%lx, ptr2=0x%lx, ptr=0x%lx, "
-               "buffer_size = 0x%x, period_size = 0x%x, bits=%d, rate=%d\n",
-               ptr1, ptr2, ptr, (int)runtime->buffer_size,
-               (int)runtime->period_size, (int)runtime->frame_bits,
-               (int)runtime->rate);
-        */
-        return ptr;
+        prev_ptr = -1;
+        do {
+                ptr = snd_ca0106_ptr_read(emu, PLAYBACK_LIST_PTR, channel);
+                ptr = (ptr >> 3) * runtime->period_size;
+                ptr += bytes_to_frames(runtime,
+                        snd_ca0106_ptr_read(emu, PLAYBACK_POINTER, channel));
+                if (ptr >= runtime->buffer_size)
+                        ptr -= runtime->buffer_size;
+                if (prev_ptr == ptr)
+                        return ptr;
+                prev_ptr = ptr;
+        } while (--timeout);
+        snd_printk(KERN_WARNING "ca0106: unstable DMA pointer!\n");
+        return 0;
 }
 
 /* pointer_capture callback */