The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one
core to go into this mode before other core. The coupled cpuidle framework
can help to sync the MPCore to coupled state then go into "powered-down"
idle mode together. The driver can just assume the MPCore come into
"powered-down" mode at the same time. No need to take care if the CPU_0
goes into this mode along and only can put it into safe idle mode (WFI).
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 for waiting CPU0 in the same state.
When the CPU0 requests powered-down state, it attempts to put the secondary
CPU into reset to prevent it from waking up. Then power down both CPUs
together and power off the cpu rail.
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".
Based on the work by:
Colin Cross <ccross@android.com>
Gary King <gking@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
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".
Based on the work by:
Colin Cross <ccross@android.com>
Gary King <gking@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
The different Tegra chips may have different CPU idle states and data.
Individual CPU idle driver make it more easy to maintain.
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Joseph Lo