On Tue, 2012-12-04 at 02:18 +0800, Stephen Warren wrote: > On 12/02/2012 08:00 PM, Joseph Lo wrote: > > The powered-down state of Tegra20 requires power gating both CPU cores. > > When the secondary CPU requests to enter powered-down state, it saves > > its own contexts and then enters WFI. The Tegra20 had a limition to > > power down both CPU cores. The secondary CPU must waits for CPU0 in > > powered-down state too. If the secondary CPU be woken up before CPU0 > > entering powered-down state, then it needs to restore its CPU states > > and waits for next chance. > > > > Be aware of that, you may see the legacy power state "LP2" in the code > > which is exactly the same meaning of "CPU power down". > > > arch/arm/mach-tegra/sleep-tegra20.S | 145 +++++++++++++++++++++++++++++++++ > > Is it actually necessary to implement those parts of the code in > assembly? It looks like it's mostly just memory read/write and a few > barriers, all of which can be coded in regular C or invoked from C. > > The reason I ask is that we eventually want to remove all hard-coded > virtual memory addresses, such as TEGRA_PMC_VIRT, and it'll be a lot > easier to access memory relative to a variable base address from C than > assembly. > > Now, perhaps we can solve this later; when we actually try to get this > code into drivers/cpuidle/ and remove the hard-coded virtual memory > addresses. Still, it'd be great if we didn't have to re-write the code > as much (from .S->.c) when making those changes... OK. Let me think how to do this for both Tegra20 and Tegra30. Thanks, Joseph -- 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
