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RFC OMAP4 cpuidle cleanup

Kevin Hilman linux-arm-kernel linux-omap 1 version New

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  1. v1 RFC Latest0 of 7 patches 0 repliesNew

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Cover letter [RFC][PATCH 0/7] OMAP4 cpuidle cleanup
Quoted 49 lines · Daniel Lezcano
Quoted 22 lines · Jean Pihet
Quoted 20 lines · Santosh Shilimkar

Daniel,

Quoted 17 lines · Daniel Lezcano

This patchset is a proposition to improve a bit the code. The changes are code cleanup and does not change the behavior of the driver itself.

A couple a things call my intention. Why the cpuidle device is set for cpu0 only and why the WFI is not used ?

Daniel Lezcano (7):
ARM: OMAP4: cpuidle - Remove unused valid field
ARM: OMAP4: cpuidle - Declare the states with the driver declaration
ARM: OMAP4: cpuidle - Remove the cpuidle_params_table table
ARM: OMAP4: cpuidle - fix static omap4_idle_data declaration
ARM: OMAP4: cpuidle - Initialize omap4_idle_data at compile time
ARM: OMAP4: cpuidle - use the omap4_idle_data variable directly
ARM: OMAP4: cpuidle - remove omap4_idle_data initialization at boot
time

Quoted 6 lines
Quoted 2 lines

The series looks fine to me in general. This clean-up is applicable for OMAP3 cpuidle code as well.

Great!
However OMAP3 has a few specific things that cannot be removed as easily:
- the 'valid' flag is used because only certain combinations of power domains states are possible,

When I look the board-rx51 code I see:

static struct cpuidle_params rx51_cpuidle_params[] = {
	/* C1 */
	{110 + 162, 5 , 1},
	/* C2 */
	{106 + 180, 309, 1},
	/* C3 */
	{107 + 410, 46057, 0},
	/* C4 */
	{121 + 3374, 46057, 0},
	/* C5 */
	{855 + 1146, 46057, 1},
	/* C6 */
	{7580 + 4134, 484329, 0},
	/* C7 */
	{7505 + 15274, 484329, 1},
};
Quoted 3 lines

If C3, C4, C6 are not valid, so AFAICS never used in the cpuidle code why the values are 'exit_latency' and 'target_residency' specified ? I mean why don't we have { 0, 0, 0 } ? Is it just for information ?

Yes, because getting those numbers were based on some board-specific measurements, and we don't want those values to be lost. Also, some usage patterns might want to (re)enable those states.

Quoted 4 lines

I understand the purpose of this code but it looks a bit tricky and hard to factor out. Is it acceptable to create a new cpuidle driver for rx51 then we factor out the code between omap3, omap4 and rx51 when all the code consistent ?

I don't like that idea. All the code is the same, the only thing we need is the ability to pass in board-specific latency numbers for the C-states.

These latency numbers are obviously quite significant when it comes to the final power consumption, and these values often depend on board-specific settings. Until there are generic frameworks for defining all the latencies involved, passing these values in from board files is absolutly needed.

Kevin

Read the cover letter in its thread