Hello, I wrote:
We have found some issues with Au1550 AC'97 OSS driver in 2.6
(sound/oss/au1550_ac97.c), though it also should concern 2.4 driver
(drivers/sound/au1550_psc.c).
First, we don't think that using readl() calls instead of au_readl() is
correct -- readl() is subject to byte-swapping etc., so may not work in
BE mode anymore and au_readl() is intended for embedded Au1550 devices for
> which the byte swapping issue is resolved automagically, and BTW the same
PSC_AC97STAT register is read "both ways" in the driver.
... for no apparent reason?
That's what the first patch is about.
Second, start_dac() grabs a spinlock already held by its caller,
au1550_write(). This doesn't show up with the standard UP spinlock
impelmentation but when the different one (mutex based) is in use, a
lockup happens. The second patch demonstates a possible solution but
here's a question: why there's no "symmetric" spinlock logic in
start_adc(), may be here exits another potential issue?
After having a look at sound/oss/au1000.c, here's an updated patch
that deals with "nested" spinlocks the same way that driver does, and adds
spinlock to start_adc() as well.
WBR, Sergei
Signed-off-by: Konstantin Baydarov <kbaidarov@xxxxxxxxxxxxx>
Signed-off-by: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>
Index: linux/sound/oss/au1550_ac97.c
===================================================================
--- linux.orig/sound/oss/au1550_ac97.c
+++ linux/sound/oss/au1550_ac97.c
@@ -463,7 +463,7 @@ stop_dac(struct au1550_state *s)
/* Wait for Transmit Busy to show disabled.
*/
do {
- stat = readl((void *)PSC_AC97STAT);
+ stat = au_readl(PSC_AC97STAT);
au_sync();
} while ((stat & PSC_AC97STAT_TB) != 0);
@@ -492,7 +492,7 @@ stop_adc(struct au1550_state *s)
/* Wait for Receive Busy to show disabled.
*/
do {
- stat = readl((void *)PSC_AC97STAT);
+ stat = au_readl(PSC_AC97STAT);
au_sync();
} while ((stat & PSC_AC97STAT_RB) != 0);
@@ -542,7 +542,7 @@ set_xmit_slots(int num_channels)
/* Wait for Device ready.
*/
do {
- stat = readl((void *)PSC_AC97STAT);
+ stat = au_readl(PSC_AC97STAT);
au_sync();
} while ((stat & PSC_AC97STAT_DR) == 0);
}
@@ -574,7 +574,7 @@ set_recv_slots(int num_channels)
/* Wait for Device ready.
*/
do {
- stat = readl((void *)PSC_AC97STAT);
+ stat = au_readl(PSC_AC97STAT);
au_sync();
} while ((stat & PSC_AC97STAT_DR) == 0);
}
@@ -1989,7 +1989,7 @@ au1550_probe(void)
/* Wait for PSC ready.
*/
do {
- val = readl((void *)PSC_AC97STAT);
+ val = au_readl(PSC_AC97STAT);
au_sync();
} while ((val & PSC_AC97STAT_SR) == 0);
@@ -2012,7 +2012,7 @@ au1550_probe(void)
/* Wait for Device ready.
*/
do {
- val = readl((void *)PSC_AC97STAT);
+ val = au_readl(PSC_AC97STAT);
au_sync();
} while ((val & PSC_AC97STAT_DR) == 0);
Signed-off-by: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>
Index: sound/oss/au1550_ac97.c
===================================================================
--- sound/oss/au1550_ac97.c~ 10 Jul 2005 10:29:03 -0000
+++ sound/oss/au1550_ac97.c 7 Nov 2005 18:14:59 -0000
@@ -607,11 +607,14 @@ static void
start_adc(struct au1550_state *s)
{
struct dmabuf *db = &s->dma_adc;
+ unsigned long flags;
int i;
if (!db->stopped)
return;
+ spin_lock_irqsave(&s->lock, flags);
+
/* Put two buffers on the ring to get things started.
*/
for (i=0; i<2; i++) {
@@ -630,6 +633,8 @@ start_adc(struct au1550_state *s)
au_sync();
db->stopped = 0;
+
+ spin_unlock_irqrestore(&s->lock, flags);
}
static int
@@ -1181,8 +1186,11 @@ au1550_write(struct file *file, const ch
if (db->nextOut >= db->rawbuf + db->dmasize)
db->nextOut -= db->dmasize;
db->total_bytes += db->dma_fragsize;
- if (db->dma_qcount == 0)
+ if (db->dma_qcount == 0) {
+ spin_unlock(&s->lock);
start_dac(s);
+ spin_lock(&s->lock);
+ }
db->dma_qcount++;
}
spin_unlock_irqrestore(&s->lock, flags);
