On Fri, 2012-12-21 at 00:55 +0800, Stephen Warren wrote:

On 12/19/2012 07:30 PM, Joseph Lo wrote:

quoted

The power up sequence is different on the cold boot CPU and the CPU
that resumed from the hotplug. For the cold boot CPU, it was been power
gated as default. To power up the cold boot CPU, the power should be
un-gated by un toggling the power gate register manually.

For the CPU that resumed from the hotplug, after un-halted the CPU. The
flow controller will un-gate the power of the CPU. No need to manually
control, just wait the power be resumed and continue the power up
sequence after the CPU power is ready.

I'd like Peter to review this too (CC'd). I guess it looks OK...

quoted

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

quoted

@@ -72,7 +75,27 @@ static int tegra30_power_up_cpu(unsigned int cpu)
 	if (pwrgateid < 0)
 		return pwrgateid;
 
-	/* If this is the first boot, toggle powergates directly. */
+	/*
+	 * If the CPU had booted and went through here after CPU
+	 * had been already un-gated by flow controller. Wait
+	 * for confirmation that the CPU is powered then remove
+	 * the IO clamps. On the cold boot entry, do not wait.
+	 */

That comment is quite unclear. In particular the first sentence says "if
something" rather than "if something then something". Can you please
re-write it?

OK.

Also, it'd be good to explain (or at least briefly reference) the boot
path for a cold-boot CPU and a warm boot CPU; I assume that somehow a
cold boot CPU doesn't execute tegra_secondary_init(), but a warm boot
CPU does?

The boot path was the same. Both of the conditions were booted from
tegra_boot_secondary. Just the power sequence has been different. We add
the code to recover the power up sequence of warm boot CPU.

Thanks,
Joseph