[sorry for HTML spam, resending] Hi, we have the problem today that cpu based performance counters don't work when we're using the big.LITTLE switcher on Exynos 5420, and it doesn't look like code exists to deal with this in the switcher.
As it stands right now, if you put an A-15 or A-7 PMU node into your device-tree on an bl_switcher system it's very broken. At the minimum, I think it should disable performance counters until there's some kind of proper implementation. I looked into trying to make this work, but it turned out to not be as simple as just context switching counters from A-15 to A-7. The biggest problem is that the PMUs are not architecturally compatible. There are different events and differing numbers of counters on these two cores. There's also the tangential issue of representing this in the device tree, but that's far less important. My guess as to how to fix this is to create an "architectural" PMU which contains the intersection of the two performance monitor units with the minimum number of counters supported by either core (which in this case looks to be 4 on the A7). However, I don't really have the bandwidth to work on this at the moment. I was mostly wondering, have other people run into this limitation and is there any sort of plan to work on it? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/