On Sun, 2009-01-11 at 03:32 +0100, hermann pitton wrote: > Hi, > > Am Samstag, den 10.01.2009, 07:37 -0500 schrieb Andy Walls: > > On Sat, 2009-01-10 at 13:02 +0100, Marcin Slusarz wrote: > > > On Fri, Jan 09, 2009 at 09:48:07PM -0500, Andy Walls wrote: > > > > 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 > > > > > > 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? > > > > > > I don't have this hardware so I can't tell. I've picked random oops from > > > kerneloops.org and tried to fix it. > > > > Ah. Good man. > > > > > > > > > > > > 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. > > > > > > Sounds good. But I think this register should be set to 0, because in > > > saa7134_irq, we do: > > > > > > report = saa_readl(SAA7134_IRQ_REPORT); > > > (...) > > > if ((report & SAA7134_IRQ_REPORT_RDCAP) || (report & SAA7134_IRQ_REPORT_INTL)) > > > saa7134_irq_video_signalchange(dev); > > > > > > But I'm not v4l expert, so... > > > > With most chip interrupt status registers, you write the flags you want > > to clear. > > > > That way you can always do something like: > > > > a = read(ISR_REG); > > write(ISR_REG,a); > > > > to clear the Interrupt status register. > > > > Note what saa7134_irq() does: > > > > report = saa_readl(SAA7134_IRQ_REPORT); > > [...] > > saa_writel(SAA7134_IRQ_REPORT,report); > > [...] > > if ((report & SAA7134_IRQ_REPORT_RDCAP) || > > (report & SAA7134_IRQ_REPORT_INTL)) > > saa7134_irq_video_signalchange(dev); > > > > > > So I'm thinking writing 0 to the register won't have the desired effect. > > > > Again, thanks for taking the initiative. > > > > Regards, > > Andy > > > > > > 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... ;) > > > > > > Hartmut has the register programming instructions under NDA and some > others obviously too. > > Must have been very lucky all that time ... If it makes the scenario seem more plausible, Marcin pointed out a website where this Oops has been reported 22 times: http://kerneloops.org/guilty.php?guilty=mute_input_7133&version=2.6.27-release&start=1802240&end=1835007&class=oops My suggested fix is this: http://linuxtv.org/hg/~awalls/cx88/rev/a28c39659c25 which should do no harm, even if it doesn't fix the Oops. Regards, Andy > Cheers, > Hermann -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
