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Re: Stability Under Load

 

On 08/21/2011 06:50 PM, Julian Andres Klode wrote:
On Sun, Aug 21, 2011 at 01:09:09PM +0100, Gordan Bobic wrote:
On 08/21/2011 12:27 PM, Julian Andres Klode wrote:
On Sun, Aug 21, 2011 at 12:06:39PM +0100, Gordan Bobic wrote:
Really? It complains about a max of 1000mV? On my AC100 975mV and
above produces no error. What model did you say you have?
Yes, a 10V. It should be fairly obvious the cpu_millivolts in
tegra2_dvfs.c includes 1100, the default level is 1100, as can
be seen in cpu_speedo_max_millivolts array, and
tegra2_dvfs_rail_vdd_cpu.

Hmm, that's interesting. So how do the differences between what's in
tegra2_dvfs.c and what's in board-paz00-power.c get reconciled?
Aren't these settings redundant?

I'm also curious how come my powertop is showing 1000MHz with no
errors in the log when I set SM1 to 975mV.
Buggy powertop?

Plausible, but /sys/devices/system/cpu/cpu?/cpufreq/cpuinfo_cur_freq also reports 1GHz.

The 1000 MHz is linked to 1100 mV in the DVFS
code, I annotated the following cpu frequency table with the
corresponding voltages.

	{ 0, 216000 },	/*  750 mV */
	{ 1, 312000 },	/*  800 mV */
	{ 2, 456000 },	/*  850 mV */
	{ 3, 608000 },	/*  900 mV */
	{ 4, 760000 },	/*  950 mV */
	{ 5, 816000 },	/* 1000 mV */
	{ 6, 912000 },	/* 1050 mV */
	{ 7, 1000000 },	/* 1100 mV */

There is no way that I can see how you would be able to get
to 1 GHz @ 1 V without also modifying the corresponding
tables in tegra2_dvfs.c:

	static const int cpu_millivolts[MAX_DVFS_FREQS] =
		{750, 775, 800, 825, 850, 875, 900, 925, 950, 975, 1000, 1025, 1050, 1100, 1125};

(indexed by the frequencies above)

And of course, adjusting:
	static const int cpu_speedo_max_millivolts[NUM_SPEED_LEVELS] =
		{ 1100, 1025, 1125 };

	static struct dvfs_rail tegra2_dvfs_rail_vdd_cpu = {
		.reg_id = "vdd_cpu",
		.max_millivolts = 1100,
		.min_millivolts = 750,
		.nominal_millivolts = 1100,
	};

which both list 1100 as the default value.

I'll have to test the speed to establish it for sure, but if what you are saying is true, then setting SM1 upper limit to 1200 should have no effect anyway, because upping the voltage limit without changing it in all the other places you list here won't cause the voltage to get as high as 1200 as per what is in the git tree. Is that right?

Gordan


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