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>

diff --git a/sound/pci/ca0106/ca0106_main.c b/sound/pci/ca0106/ca0106_main.c
index 0a3d3d6e77b4d668bad27a929cda8fa174d1cd1c..8e69620da20be445eaf3cd5623dbe2d4c2669c1a 100644 (file)
--- 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 */