ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode

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>

1 files changed, 53 insertions, 0 deletions

diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S
index 1074364e77ee..9f6bfafdd512 100644
--- a/arch/arm/mach-tegra/sleep-tegra20.S
+++ b/arch/arm/mach-tegra/sleep-tegra20.S
@@ -57,6 +57,9 @@ ENDPROC(tegra20_hotplug_shutdown)
 ENTRY(tegra20_cpu_shutdown)
         cmp     r0, #0
         moveq   pc, lr                  @ must not be called for CPU 0
+        mov32   r1, TEGRA_PMC_VIRT + PMC_SCRATCH41
+        mov     r12, #CPU_RESETTABLE
+        str     r12, [r1]
 
         cpu_to_halt_reg r1, r0
         ldr     r3, =TEGRA_FLOW_CTRL_VIRT
@@ -163,6 +166,21 @@ ENTRY(tegra20_cpu_set_resettable_soon)
 ENDPROC(tegra20_cpu_set_resettable_soon)
 
 /*
+ * tegra20_cpu_is_resettable_soon(void)
+ *
+ * Returns true if the "resettable soon" flag in PMC_SCRATCH41 has been
+ * set because it is expected that the secondary CPU will be idle soon.
+ */
+ENTRY(tegra20_cpu_is_resettable_soon)
+        mov32   r1, TEGRA_PMC_VIRT + PMC_SCRATCH41
+        ldr     r12, [r1]
+        cmp     r12, #CPU_RESETTABLE_SOON
+        moveq   r0, #1
+        movne   r0, #0
+        mov     pc, lr
+ENDPROC(tegra20_cpu_is_resettable_soon)
+
+/*
  * tegra20_sleep_cpu_secondary_finish(unsigned long v2p)
  *
  * Enters WFI on secondary CPU by exiting coherency.
@@ -221,4 +239,39 @@ ENTRY(tegra20_sleep_cpu_secondary_finish)
 
         ldmfd   sp!, {r4 - r11, pc}
 ENDPROC(tegra20_sleep_cpu_secondary_finish)
+
+/*
+ * tegra20_tear_down_cpu
+ *
+ * Switches the CPU cluster to PLL-P and enters sleep.
+ */
+ENTRY(tegra20_tear_down_cpu)
+        bl      tegra_switch_cpu_to_pllp
+        b       tegra20_enter_sleep
+ENDPROC(tegra20_tear_down_cpu)
+
+/*
+ * tegra20_enter_sleep
+ *
+ * uses flow controller to enter sleep state
+ * executes from IRAM with SDRAM in selfrefresh when target state is LP0 or LP1
+ * executes from SDRAM with target state is LP2
+ */
+tegra20_enter_sleep:
+        mov32   r6, TEGRA_FLOW_CTRL_BASE
+
+        mov     r0, #FLOW_CTRL_WAIT_FOR_INTERRUPT
+        orr     r0, r0, #FLOW_CTRL_HALT_CPU_IRQ | FLOW_CTRL_HALT_CPU_FIQ
+        cpu_id  r1
+        cpu_to_halt_reg r1, r1
+        str     r0, [r6, r1]
+        dsb
+        ldr     r0, [r6, r1] /* memory barrier */
+
+halted:
+        dsb
+        wfe     /* CPU should be power gated here */
+        isb
+        b       halted
+
 #endif