On 08/06/2013 03:41 AM, Joseph Lo wrote:

On Tue, 2013-08-06 at 01:48 +0800, Stephen Warren wrote:

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On 08/05/2013 05:21 AM, Joseph Lo wrote:

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The LP1 suspending mode on Tegra means CPU rail off, devices and PLLs are
clock gated and SDRAM in self-refresh mode. That means the low level LP1
suspending and resuming code couldn't be run on DRAM and the CPU must
switch to the always on clock domain (a.k.a. CLK_M 12MHz oscillator). And
the system clock (SCLK) would be switched to CLK_S, a 32KHz oscillator.
The LP1 low level handling code need to be moved to IRAM area first. And
marking the LP1 mask for indicating the Tegra device is in LP1. The CPU
power timer needs to be re-calculated based on 32KHz that was originally
based on PCLK.

When resuming from LP1, the LP1 reset handler will resume PLLs and then
put DRAM to normal mode. Then jumping to the "tegra_resume" that will
restore full context before back to kernel. The "tegra_resume" handler
was expected to be found in PMC_SCRATCH41 register.

This is common LP1 procedures for Tegra, so we do these jobs mainly in
this patch:
* moving LP1 low level handling code to IRAM
* marking LP1 mask
* copying the physical address of "tegra_resume" to PMC_SCRATCH41
* re-calculate the CPU power timer based on 32KHz

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

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@@ -174,14 +181,75 @@ enum tegra_suspend_mode tegra_pm_validate_suspend_mode(
 				enum tegra_suspend_mode mode)
 {
 	/*
-	 * The Tegra devices only support suspending to LP2 currently.
+	 * The Tegra devices support suspending to LP1 or lower currently.
 	 */
-	if (mode > TEGRA_SUSPEND_LP2)
-		return TEGRA_SUSPEND_LP2;
+	if (mode > TEGRA_SUSPEND_LP1)
+		return TEGRA_SUSPEND_LP1;
 
 	return mode;
 }

I think that change needs to happen after patch 7. At this point in the
series, LP1 doesn't work on any chip. After patch 7, it will work on all
chips.

This code is safe here. Because we have some protection code.

...

We have the function (tegra_lp1_iram_hook and tegra_sleep_core_init) to
check if the system didn't support LP1 yet, then it will fall back to
LP2. I verified this too.

Ah yes, that looks fine. Thanks very much for the explanation.

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Note: You must assume that the DT changes are all checked in before any
of the code changes, so the code needs to work correctly even if the DT
contains the data that allows usage of LP1 before the driver actually
implements LP1.

So should I still move them to the last patch?

No, I think given the check in tegra_lp1_iram_hook, everything will work
fine no matter which order the DT and code changes are applied.