Subject: [PATCH v4] ARM: SMP_TWD: make setup()/stop() reentrant

From: [email-masked] (Santosh Shilimkar)
Date: Mon, 22 Oct 2012 18:51:29 +0530

On Monday 22 October 2012 06:45 PM, Linus Walleij wrote:
> From: Linus Walleij <[email-masked]>
>
> It has been brought to my knowledge that the .setup()/.stop()
> function pair in the SMP TWD is going to be called from atomic
> contexts for CPUs coming and going, and then the
> clk_prepare()/clk_unprepare() calls cannot be called
> on subsequent .setup()/.stop() iterations. This is however
> just the tip of an iceberg as the function pair is not
> designed to be reentrant at all.
>
> This change makes the SMP_TWD clock .setup()/.stop() pair reentrant
> by splitting the .setup() function in three parts:
>
> - One COMMON part that is executed the first time the first CPU
>    in the TWD cluster is initialized. This will fetch the TWD
>    clk for the cluster and prepare+enable it. If no clk is
>    available it will calibrate the rate instead.
>
> - One part that is executed the FIRST TIME a certain CPU is
>    brought on-line. This initializes and sets up the clock event
>    for a certain CPU.
>
> - One part that is executed on every subsequent .setup() call.
>    This will re-initialize the clock event. This is augmented
>    to call the clk_enable()/clk_disable() pair properly.
>
> Cc: Shawn Guo <[email-masked]>
> Reported-by: Peter Chen <[email-masked]>
> Signed-off-by: Linus Walleij <[email-masked]>
> ---
> ChangeLog v3->v4:
> - Skip clk_enable()/clk_disable() in subsequent call after common
>    initialization - there is no way we can turn off the clock that
>    is running us anyway.
> - Move common_setup_called variable assignment into the if-clause
> ---

Looks good now. Thanks for the update.

Reviewed-by: Santosh Shilimkar <[email-masked]>