On Tue, 31 May 2011, Daniel Drake wrote: > On 31 May 2011 21:33, Per Forlin <per.forlin@xxxxxxxxxx> wrote: > > Daniel Drake reported an issue in the libertas sdio client that was > > triggered by the sdio_single_irq functionality. His SDIO device seems to > > raise an interrupt even though there are no bits set in the CCCR_INTx > > register. This behaviour is not supported by the sdio_single_irq feature nor > > the SDIO spec. The purpose of the sdio_single_irq feature is to avoid the > > overhead of checking the CCCR_INTx registers, this result in no error > > handling of the case if there is a pending IRQ with none CCCR_INTx bits set. > > Thanks a lot for diagnosing this and nice work on figuring out the > root cause presumably without even having access to the hardware! > > I've looked further, based on your findings, and have found that you > are correct. During initialisation, exactly one interrupt is received > with CCCR_INTx=0. Previously the mmc stack threw this interrupt away, > after the optimization it now calls into libertas before it is ready > to handle interrupts, leading to the crash. From that point, all other > interrupts that come in are "normal". > > This is definitely a weird hardware issue, and it would annoy me for > this hardware to cause a second generic mmc layer feature be disabled > by default! And actually it is not much work to harden up the libertas > driver to be able to accept that spurious IRQ, and during the process > of fixing that it actually made the spurious IRQ go away completely. > > Patch attached. > > So, I vote for that we work around this little hardware issue in the > libertas driver, and leave this optimization enabled by default until > we find a hardware issue that is more difficult to workaround. I can > take on submission of the libertas patch. > > Thoughts? This is definitively the best approach. Thanks for fixing the root cause. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
