Prior to this change, {save,restore}_cpu_arch_register() collaborated to
maintain the value of the CPU diagnostic register across power cycles.
This was required to maintain any CPU errata workaround enable bits in
that register. However, now that the Tegra reset vector code always
enables all required workarounds, there is no need to save and restore
the diagnostic register; it is always explicitly programmed in the
required manner.
Hence, remove the save/restore logic.
This has the advantage that the kernel always directly controls the value
of this register every boot, rather than relying on a bootloader or other
kernel code having previously written the correct value into it. This
makes CPU0 (which was previously saved/restored) and CPUn (which should
have been set up by the reset vector) be controlled in exactly the same
way, which is easier to debug/find/...
In particular, when converting Tegra to a multi-platform kernel, the CPU0
diagnostic register value initially comes from the bootloader. Most Tegra
bootloaders don't yet enable all required CPU bug workarounds. The
previous commit updates the kernel to do so on any CPU power cycle.
However, the save/restore code ends up over-writing the value with the
old bootloader-driven value instead of the now more-likely-to-be-correct
kernel value!
Even irrespective of multi-platform conversion, this change limits the
kernel's exposure to any WARs the bootloader didn't enable for CPU0: on
the very first LP2 transition (CPU power-saving which power-cycles the
CPU), the correct value will be enabled.
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>
tegra_cpu_car_ops struct is going to be accessed from drivers/clk/tegra.
Move the tegra_cpu_car_ops to include/linux/clk/tegra.h.
Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
There are some redundant codes in the CPUINIT section that was caused by
some codes not be organized well in "headsmp.S". Currently all the codes
in "headsmp.S" were put into CPUINIT section. But actually it doesn't
need to be loacted in CPUINIT section. There is no fuction access them
in CPUINIT section and we will relocate them to IRAM.
These codes also caused some unnecessary functions that access these
codes been put into CPUINIT section too. This patch clean it up and put
them into normal text section.
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
The L2 RAM is in different power domain from the CPU cluster. So the
L2 content can be retained over CPU suspend/resume. To do that, we
need to disable L2 after the MMU is disabled, and enable L2 before
the MMU is enabled. But the L2 controller is in the same power domain
with the CPU cluster. We need to restore it's settings and re-enable
it after the power be resumed.
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
This is a power gating idle mode. It support power gating vdd_cpu rail
after all cpu cores in "powered-down" status. For Tegra30, the CPU0 can
enter this state only when all secondary CPU is offline. We need to take
care and make sure whole secondary CPUs were offline and checking the
CPU power gate status. After that, the CPU0 can go into "powered-down"
state safely. Then shut 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".
Base on the work by:
Scott Williams <scwilliams@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
This supports power-gated idle on secondary CPUs for Tegra30. The
secondary CPUs can go into powered-down state independently. When
CPU goes into this state, it saves it's contexts and puts itself
to flow controlled WFI state. After that, it will been power gated.
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:
Scott Williams <scwilliams@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Stephen Warren
Joseph Lo
Prashant Gaikwad