Skip to content

RFC OMAP4 cpuidle cleanup

Daniel Lezcano linux-arm-kernel linux-omap 1 version New

Get series with b4
b4 am [email protected]

Versions newest first

  1. v1 RFC Latest0 of 7 patches 0 repliesNew

Patches in v1 No applies recorded yet

None of the 7 patches the cover letter announces are in this archive.

Reviews trailers per patch

No Reviewed-by, Acked-by or Tested-by trailers for v1 yet.

Read the v1 thread

Cover letter [RFC][PATCH 0/7] OMAP4 cpuidle cleanup
Quoted 51 lines · Kevin Hilman
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 7 lines
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.

When you say re-enable you mean for a custom kernel ?

Quoted 8 lines
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.

Sorry I was not clear, I was not saying duplicating the code. What I meant is to create a driver:

struct cpuidle_driver rx51_idle_driver = {
.name = "rx51_idle",

	.owner = 	THIS_MODULE,
	.states = {
		{
			/* What is in rx51_cpuidle_params */
		}
	};

We put in there only the valid fields and we keep in a comment the table with the latency numbers.

Assuming the valid field is for handling the table overwritting, we can then remove it. By this way, we simplify the next_valid_state function.

Depending if we have rx51 or not, we register the rx51 driver or the omap3 driver in the init function. That has also the benefit to group the cpuidle code in the cpuidle34xx file.

Quoted 5 lines

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.

Yes but before creating the generic framework, we have to do a transversal cpuidle consolidation across the SoC, factor out the code when possible, and ensure the consistency between the different platform and see a common pattern to emerge from this work.

Signature · 5 lines
  <http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

Read the cover letter in its thread