linux-kernel - Re: [PATCH 2/4]: CPUIDLE: Introduce architecture independent cpuidle_pm

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Message-Id: <1251442085.18584.120.camel@twins>
Date:	Fri, 28 Aug 2009 08:48:05 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	arun@...ux.vnet.ibm.com
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/4]: CPUIDLE: Introduce architecture independent
 cpuidle_pm_idle in drivers/cpuidle/cpuidle.c

On Fri, 2009-08-28 at 11:44 +0530, Arun R Bharadwaj wrote:
> * Peter Zijlstra <a.p.zijlstra@...llo.nl> [2009-08-27 14:53:27]:
> 
> Hi Peter, Ben,
> 
> I've put the whole thing in a sort of a block diagram. Hope it
> explains things more clearly.
> 
> 
> 
> 
> 
> 
> 				----------------
> 				|    CPUIDLE   |  (Select idle states like
> 				|   GOVERNORS  |   C1, C1e, C6 etc in case
> 				| (Menu/Ladder)|   x86 & nap, snooze in
> 				|	       |   case of POWER - based on
> 				----------------   latency & power req)
> 					^
> 					|
> 					|
> 					|
> 					|
> 					|
>   ----------			-----------------	         -------------
>   |	   |			|		|	         |  PSERIES  |
>   |  ACPI  |------------------>	|    CPUIDLE	| <--------------|   IDLE    |
>   |	   |			|		|	         |           |
>   ----------			-----------------	         -------------
> 
> Main idle routine- pm_idle()			         Main idle routine-
> 							     ppc_md.power_save()
> 
> pm_idle = cpuidle_pm_idle;			         ppc_md.power_save =
> (start using cpuidle's idle				      cpuidle_pm_idle();
>  loop, which internally calls
>  governor to select the right
>  state to go into).
> 
> 
> Relavent code snippet from drivers/cpuidle/cpuidle.c
> -------------------------------------
> 
> static void cpuidle_idle_call(void)
> {
> 	............
> 	............
> 
> 	/* Call the menu_select() to select the idle state to enter. */
> 	next_state = cpuidle_curr_governor->select(dev);
> 
> 	............
> 	............
> 
> 	/*
> 	 * Enter the idle state previously selected. target_state->enter
> 	 * would call pseries_cpuidle_loop() which selects nap/snooze
> 	 * /
> 	dev->last_residency = target_state->enter(dev, target_state);
> }
> 
> void cpuidle_install_idle_handler(void)
> {
> 	.........
> 	.........
> 	cpuidle_pm_idle = cpuidle_idle_call;
> }

All I'm seeing here is a frigging mess.

How on earths can something called: cpuidle_install_idle_handler() have
a void argument, _WHAT_ handler is it going to install?

So somehow you added to the ACPI mess by now having 3 wild function
pointers, that's _NOT_ progress.

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