On Fri, 2012-12-21 at 01:43 +0800, Stephen Warren wrote:

On 12/17/2012 07:30 PM, Joseph Lo wrote:

quoted

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".

quoted

diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c

quoted

 int __init tegra20_cpuidle_init(void)

quoted

+	drv->state_count = sizeof(tegra_idle_states) /
+			   sizeof(struct cpuidle_state);

Use ARRAY_SIZE() there?

OK.

quoted

+	for (i = 0; i < drv->state_count; i++)
+		memcpy(&drv->states[i], &tegra_idle_states[i],
+		       sizeof(struct cpuidle_state));

Can't you call memcpy() once:

memcpy(drv->states, tegra_idle_states,
		drv->state_count * sizeof(drv->states[0]));

... although I personally much preferred when all this was just static
initialization directly in tegra_idle_driver, rather than all this messy
copying. Really, struct cpuidle_driver should point at the array, rather
than including it.

I think so. If you strongly prefer the original style, I can rollback to
the previous version here.

quoted

diff --git a/arch/arm/mach-tegra/pm.c b/arch/arm/mach-tegra/pm.c

quoted

@@ -173,6 +173,8 @@ bool __cpuinit tegra_set_cpu_in_lp2(int phy_cpu_id)
 
 	if ((phy_cpu_id == 0) && cpumask_equal(cpu_lp2_mask, cpu_online_mask))
 		last_cpu = true;
+	else if (phy_cpu_id == 1)
+		tegra20_cpu_set_resettable_soon();
 
 	spin_unlock(&tegra_lp2_lock);
 	return last_cpu;

Shouldn't the code in that else branch have a run-time check for whether
it's running on Tegra20? When compiled without Tegra20 support,
tegra20_cpu_set_resettable_soon() is a dummy static inline, but when
both Tegra20 and Tegra30 are compiled in, isn't that code going to run
when it shouldn't; pm.c being a common file.

Because the code didn't hurt Tegra30, so I didn't add a runtime
detection there. If you have concern, I can add runtime detection there.

Thanks,
Joseph