via82xx calc_linear_pos bug

via82xx calc_linear_pos bug

[Timo Hirvonen]

[-- Attachment #1: Type: text/plain, Size: 689 bytes --]

After playing about 10-20 seconds snd_pcm_status_get_avail returns too
large value (1972895704, 1972895664 ..).

Tested kernels:

	2.6.7-mm1	works
	2.6.7-mm2	broken
	2.6.8-rc1-mm1	broken

lspci -v 
0000:00:11.5 Multimedia audio controller: VIA Technologies, Inc. VT8233/A/8235 AC97 Audio Controller (rev 50)
        Subsystem: VIA Technologies, Inc.: Unknown device 4161
        Flags: medium devsel, IRQ 22
        I/O ports at e800
        Capabilities: [c0] Power Management version 2

Attached patch (against 2.6.8-rc1-mm1) changes calc_linear_pos to the
state it was in 2.6.7-mm1.

I don't understand the code so this might not be right solution to this
problem but it seems to work.

[-- Attachment #2: via82xx-calc_linear_pos.patch --]
[-- Type: text/x-patch, Size: 630 bytes --]

--- sound/pci/via82xx.c.orig	2004-07-23 16:16:23.000000000 +0300
+++ sound/pci/via82xx.c	2004-07-23 16:16:40.000000000 +0300
@@ -715,11 +715,7 @@ static inline unsigned int calc_linear_p
 	unsigned int size, res;
 
 	size = viadev->idx_table[idx].size;
-	/* FIXME: is this always true? */
-	if (count)
-		res = viadev->idx_table[idx].offset + size - count;
-	else
-		res = viadev->idx_table[idx].offset;
+	res = viadev->idx_table[idx].offset + size - count;
 
 	/* check the validity of the calculated position */
 	if (size < count || (res < viadev->lastpos && (res >= viadev->bufsize2 || viadev->lastpos < viadev->bufsize2))) {

Re: via82xx calc_linear_pos bug

[Takashi Iwai]

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At Fri, 23 Jul 2004 18:47:30 +0300,
Timo Hirvonen wrote:
> 
> After playing about 10-20 seconds snd_pcm_status_get_avail returns too
> large value (1972895704, 1972895664 ..).

Grrr, the empire strikes again.

The change in the recent version was a workaround to fix the similar
bug on many buggy mobos.
Could you try the attached patch?


Takashi

[-- Attachment #2: Type: text/plain, Size: 2389 bytes --]

Index: alsa-kernel/pci/via82xx.c
===================================================================
RCS file: /suse/tiwai/cvs/alsa/alsa-kernel/pci/via82xx.c,v
retrieving revision 1.122
diff -u -r1.122 via82xx.c
--- alsa-kernel/pci/via82xx.c	15 Jul 2004 14:55:29 -0000	1.122
+++ alsa-kernel/pci/via82xx.c	27 Jul 2004 13:37:25 -0000
@@ -707,29 +707,36 @@
 /*
  * calculate the linear position at the given sg-buffer index and the rest count
  */
+
+#define check_invalid_pos(viadev,pos) \
+	((pos) < viadev->lastpos && ((pos) >= viadev->bufsize2 || viadev->lastpos < viadev->bufsize2))
+
 static inline unsigned int calc_linear_pos(viadev_t *viadev, unsigned int idx, unsigned int count)
 {
 	unsigned int size, res;
 
 	size = viadev->idx_table[idx].size;
-	/* FIXME: is this always true? */
-	if (count)
-		res = viadev->idx_table[idx].offset + size - count;
-	else
-		res = viadev->idx_table[idx].offset;
+	res = viadev->idx_table[idx].offset + size - count;
 
 	/* check the validity of the calculated position */
-	if (size < count || (res < viadev->lastpos && (res >= viadev->bufsize2 || viadev->lastpos < viadev->bufsize2))) {
+	if (size < count) {
+		snd_printd(KERN_ERR "invalid via82xx_cur_ptr (size = %d, count = %d)\n", (int)size, (int)count);
+		res = viadev->lastpos;
+	} else if (check_invalid_pos(viadev, res)) {
 #ifdef POINTER_DEBUG
 		printk("fail: idx = %i/%i, lastpos = 0x%x, bufsize2 = 0x%x, offsize = 0x%x, size = 0x%x, count = 0x%x\n", idx, viadev->tbl_entries, viadev->lastpos, viadev->bufsize2, viadev->idx_table[idx].offset, viadev->idx_table[idx].size, count);
 #endif
-		/* count register returns full size when end of buffer is reached */
-		if (size != count) {
+		if (count && size < count) {
 			snd_printd(KERN_ERR "invalid via82xx_cur_ptr, using last valid pointer\n");
 			res = viadev->lastpos;
 		} else {
-			res = viadev->idx_table[idx].offset + size;
-			if (res < viadev->lastpos && (res >= viadev->bufsize2 || viadev->lastpos < viadev->bufsize2)) {
+			if (! count)
+				/* bogus count 0 on the DMA boundary? */
+				res = viadev->idx_table[idx].offset;
+			else
+				/* count register returns full size when end of buffer is reached */
+				res = viadev->idx_table[idx].offset + size;
+			if (check_invalid_pos(viadev, res)) {
 				snd_printd(KERN_ERR "invalid via82xx_cur_ptr (2), using last valid pointer\n");
 				res = viadev->lastpos;
 			}

Re: via82xx calc_linear_pos bug

[Timo Hirvonen]

On Tue, 2004-07-27 at 15:39 +0200, Takashi Iwai wrote:
> At Fri, 23 Jul 2004 18:47:30 +0300,
> Timo Hirvonen wrote:
> > 
> > After playing about 10-20 seconds snd_pcm_status_get_avail returns too
> > large value (1972895704, 1972895664 ..).
> 
> Grrr, the empire strikes again.
> 
> The change in the recent version was a workaround to fix the similar
> bug on many buggy mobos.
> Could you try the attached patch?

That patch works.  snd_pcm_status_get_avail returns now sane values
again.  I don't see any "invalid via82xx_cur_ptr" messages so the code
seems to be correct now.

thanks




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Re: via82xx calc_linear_pos bug

[Takashi Iwai]

At Tue, 27 Jul 2004 17:53:37 +0300,
Timo Hirvonen wrote:
> 
> On Tue, 2004-07-27 at 15:39 +0200, Takashi Iwai wrote:
> > At Fri, 23 Jul 2004 18:47:30 +0300,
> > Timo Hirvonen wrote:
> > > 
> > > After playing about 10-20 seconds snd_pcm_status_get_avail returns too
> > > large value (1972895704, 1972895664 ..).
> > 
> > Grrr, the empire strikes again.
> > 
> > The change in the recent version was a workaround to fix the similar
> > bug on many buggy mobos.
> > Could you try the attached patch?
> 
> That patch works.  snd_pcm_status_get_avail returns now sane values
> again.  I don't see any "invalid via82xx_cur_ptr" messages so the code
> seems to be correct now.

Ok, I applied the patch to cvs.


thanks for testing.

Takashi


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