On Tue, May 07, 2013 at 04:54:31PM +0200, Stephen Warren wrote: > On 05/07/2013 07:08 AM, Thierry Reding wrote: > > On Tue, May 07, 2013 at 03:48:49PM +0300, Peter De Schrijver > > wrote: > >> On Mon, May 06, 2013 at 10:39:04PM +0200, Stephen Warren wrote: > >>> From: Stephen Warren <swarren@xxxxxxxxxx> > >>> > >>> Tegra20 HW appears to have a bug such that PCIe device > >>> interrupts, whether they are legacy IRQs or MSI, are lost when > >>> LP2 is enabled. To work around this, simply disable LP2 if the > >>> PCI driver and DT node are both enabled. > >>> > >> > >> Wouldn't it make more sense to disable LP2 when we actually > >> detect a PCIe device? > > I did consider that, but rejected the idea for the reasons Thierry > mentioned. > > > I'm not sure a patch to do so would be as simple as this one. For > > one, the cpuidle framework will already have been initialized when > > PCIe enumeration completes. So some way of permanently disabling > > one state at runtime would be required and I don't think cpuidle > > provides an API to do so. I know the latter isn't really a good > > reason, but I don't think adding that kind of API just because > > Tegra20 seems to have a bug would be appropriate. > > There is a way to do this, since it can be done via sysfs, but I don't > think it's exposed as an API from cpuidle. I agree it seems a little > silly to expose it just to support this HW bug though. > > > Furthermore, it is quite likely that the PCIe controller will only > > be enabled in DT for devices that actually have a PCIe device > > hooked up. > That's not always true though. Eg Harmony has a miniPCIe slot, so it should be listed in DT, but there is not necessarily a card present in the slot. Cheers, Peter. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
