Re: [RFC PATCH v4 0/4] Consolidate cpuidle timekeeping and irq enabling

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Maintainers for drivers/cpuidle, do you have any comments/opinions
about this patch?

Intel cpuidle and acpi cpuidle maintainers, do you have any
comments/opinions about this patch and the changes to your code?

Any other review and comments welcome.

Summary of positive and negatives as I understand them so far:

version 1, 2, and 3 (Original "wrapper" method of consolidating
timekeeping and interrupt enabling)
+ opportunistically provides consolidation for simple platform cpuidle
implementations without disturbing the more complex implementations.
By simple, I mean those at can be wrapped in the time keeping calls
and interrupt enabling calls without significantly affecting idle time
keeping accuracy or interrupt latency
- Does not provide consolidation for the more complex platform cpuidle
implementations
- Adds an additional interface, perhaps unnecessarily if this
consolidation could be done in cpuidle

version 4 (modifications to drivers/cpuidle/cpuidle.c cpuidle_idle_call)
+ Adds consolidation work to cpuidle_idle_call which allows all
platform timekeeping / interrupt handling to be consolidated.
- Requires splitting up of more complex platform cpuidle
implementations, adding further complexity and risk of breaking
something.
? Allows both pre_enter or enter to change the idle state.  Is there
an objection to this?
? Splitting up the enter functions can require additional function
calls.  Is there any concern that this is significant additional
overhead?

Thanks,
Rob


On Tue, Jan 31, 2012 at 7:00 PM, Robert Lee <rob.lee@xxxxxxxxxx> wrote:
> This patch series moves the timekeeping and irq enabling from the platform
> code to the core cpuidle driver.  Also, the platform irq disabling was removed
> as it appears that all calls into cpuidle_call_idle will have already called
> local_irq_disable().
>
> To save reviewers time, only a few platforms which required the most changes
> are included in this version.  If these changes are approved, the next version
> will include the remaining platform code which should require minimal changes.
>
> For those who have followed the previous patch versions, as you know, the
> previous version of this patch series added some helper functionality which
> used a wrapper function to remove the time keeping and irq enabling/disabling
> from the platform code.  There was also initialization helper functionality
> which has now been removed from this version.  If the basic implementation
> in this version is approved, then a separate patch submission effort can be
> made to focus on consolidation of initialziation functionality.
>
> Based on 3.3-rc1
>
> v3 submission can be found here:
> http://www.spinics.net/lists/arm-kernel/msg156751.html
> Changes since v3:
> * Removed drivers/cpuidle/common.c
> ** Removed the initialization helper functions
> ** Removed the wrapper used to consolidate time keeping and irq enable/disable
> * Add time keeping and local_irq_disable handling in cpuidle_call_idle().
> * Made necessary modifications to a few platforms that required the most changes
> ** Note on omap3: changed structure of omap3_idle_drvdata and added
>   per_next_state and per_saved_state vars to accomodate new framework.
>
> v2 submission can be found here:
> http://comments.gmane.org/gmane.linux.ports.arm.kernel/144199
>
> Changes since v2:
> * Made various code organization and style changes as suggested in v1 review.
> * Removed at91 use of common code.  A separate effort is underway to clean
> at91 code and the author has offered to convert to common interface as part
> of those changes (if this common interface is accepted in time).
> * Made platform cpuidle_driver objects __initdata and dynamically added one
> persistent instance of this object in common code.
> * Removed imx5 pm usage of gpc_dvfs clock as it is no longer needed after
> being enabled during clock initialization.
> * Re-organized patches.
>
> v1 submission can be found here:
> http://comments.gmane.org/gmane.linux.ports.arm.kernel/142791
>
> Changes since v1:
> * Common interface moved to drivers/cpuidle and made non arch-specific.
> * Made various fixes and suggested additions to the common cpuidle
> code from v1 review.
> * Added callback for filling in driver_data field as needed.
> * Modified the various platforms with these changes.
>
> Robert Lee (4):
>  cpuidle: Add time keeping and irq enabling
>  ARM: omap: Remove cpuidle timekeeping and irq enable/disable
>  acpi: Remove cpuidle timekeeping and irq enable/disable
>  x86: Remove cpuidle timekeeping and irq enable/disable
>
>  arch/arm/mach-omap2/cpuidle34xx.c |   96 ++++++++----------
>  drivers/acpi/processor_idle.c     |  203 ++++++++++++++++++++++---------------
>  drivers/cpuidle/cpuidle.c         |   75 +++++++++++---
>  drivers/idle/intel_idle.c         |  110 ++++++++++++++------
>  include/linux/cpuidle.h           |   26 +++--
>  5 files changed, 317 insertions(+), 193 deletions(-)
>

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