On Thu, 2009-01-08 at 00:50 -0200, Mauro Carvalho Chehab wrote:
> On Sun, 4 Jan 2009 22:57:42 +0100
> Marcin Slusarz <marcin.slusarz@xxxxxxxxx> wrote:
>
> > Hi
> > There's a race between saa7134 device initialization and first interrupt
> > handler, which manifests as an oops [1].
> >
> > saa7134_initdev -> request_irq -> saa7134_irq ->
> > saa7134_irq_video_signalchange -> saa7134_tvaudio_setmute -> mute_input_7133
> >
> > In mute_input_7133 dev->input == NULL and accessing dev->input->amux will oops,
> > because dev->input would be initialized later:
> >
> > saa7134_initdev -> saa7134_hwinit2 -> saa7134_video_init2 -> video_mux ->
> > saa7134_tvaudio_setinput
> >
> > I'm not sure how it should be fixed correctly, but one of attached patches
> > should fix the symptom.
> >
> > Marcin
>
> Hi Marcin,
>
> Probably, it is some locking trouble on saa7134 driver that appeared on 2.6.27,
> with the lack of KBL on newer kernels. cx88 driver is suffering similar
> troubles starting with 2.6.27.
>
> I'll try to find some time to review, but it would be better if someone volunteer himself to take a look on cx88 and saa7134 locks.
Mauro & Marcin,
This isn't a locking issue. This is a device initialization issue. It
also looks like it's been reported quite often under 2.6.25 as well.
Marcin,
What devices share the interrupt with the SAA7133?
$ cat /proc/interrupts
And could on of those those devices possibly generate an interrupt while
the saa7134 driver is being modporbe'd?
Mauro & Marcin,
This looks like to me what is going on:
saa7134_hwinit1() does properly turn off IRQs for which it wants
reports:
saa_writel(SAA7134_IRQ1, 0);
saa_writel(SAA7134_IRQ2, 0);
but not clearing the state of SAA7134_IRQ_REPORT, maybe something like
this (I don't have a SAA7134 datasheet):
saa_writel(SAA7134_IRQ_REPORT, 0xffffffff);
So when saa7134_initdev() calls request_irq(..., saa7134_irq,
IRQF_SHARED | IRQF_DISABLED, ...), it gets an IRQ that is shared with
another device.
Before saa7134_hwinit2() is called by saa7134_initdev() to set
"dev->input", some other device fires an interrupt and saa7134_irq() is
called that then operates on the unknown state of the SAA7134_IRQ_REPORT
register that was never cleared.
Marcin has mapped out the oops from there.
So the solution, I'm guessing, is likely to clear the SAA7134_IRQ_REPORT
register in saa7134_hwinit1().
If only I had a datasheet, hardware, spare time... ;)
Regards,
Andy
> Cheers,
> Mauro.
>
>
> > [1] http://kerneloops.org/guilty.php?guilty=mute_input_7133&version=2.6.27-release&start=1802240&end=1835007&class=oops
> >
> > ---
> > diff --git a/drivers/media/video/saa7134/saa7134-video.c b/drivers/media/video/saa7134/saa7134-video.c
> > index 02bb674..fcb0b17 100644
> > --- a/drivers/media/video/saa7134/saa7134-video.c
> > +++ b/drivers/media/video/saa7134/saa7134-video.c
> > @@ -2585,7 +2585,8 @@ void saa7134_irq_video_signalchange(struct saa7134_dev *dev)
> > /* no video signal -> mute audio */
> > if (dev->ctl_automute)
> > dev->automute = 1;
> > - saa7134_tvaudio_setmute(dev);
> > + if (dev->input)
> > + saa7134_tvaudio_setmute(dev);
> > } else {
> > /* wake up tvaudio audio carrier scan thread */
> > saa7134_tvaudio_do_scan(dev);
> > ---
> >
> > or
> >
> > ---
> > diff --git a/drivers/media/video/saa7134/saa7134-tvaudio.c b/drivers/media/video/saa7134/saa7134-tvaudio.c
> > index 76b1640..75ee085 100644
> > --- a/drivers/media/video/saa7134/saa7134-tvaudio.c
> > +++ b/drivers/media/video/saa7134/saa7134-tvaudio.c
> > @@ -917,6 +917,8 @@ int saa7134_tvaudio_rx2mode(u32 rx)
> >
> > void saa7134_tvaudio_setmute(struct saa7134_dev *dev)
> > {
> > + if (!dev->input)
> > + return;
> > switch (dev->pci->device) {
> > case PCI_DEVICE_ID_PHILIPS_SAA7130:
> > case PCI_DEVICE_ID_PHILIPS_SAA7134:
> > ---
>
>
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