[PATCH 1/2] clk: introduce optional disable_unused callback

[Mike Turquette]

On Wed, Dec 5, 2012 at 8:13 AM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> On 4 December 2012 22:00, Mike Turquette <mturquette at linaro.org> wrote:
>> Some gate clocks have special needs which must be handled during the
>> disable-unused clocks sequence.  These needs might be driven by software
>> due to the fact that we're disabling a clock outside of the normal
>> clk_disable path and a clk's enable_count will not be accurate.  On the
>> other hand a specific hardware programming sequence might need to be
>> followed for this corner case.
>>
>> This change is needed for the upcoming OMAP port to the common clock
>> framework.  Specifically, it is undesirable to treat the disable-unused
>> path identically to the normal clk_disable path since other software
>> layers are involved.  In this case OMAP's clockdomain code throws WARNs
>> and bails early due to the clock's enable_count being set to zero.  A
>> custom callback mitigates this problem nicely.
>>
>> Cc: Paul Walmsley <paul at pwsan.com>
>> Signed-off-by: Mike Turquette <mturquette at linaro.org>
>> ---
>>  drivers/clk/clk.c            |   13 +++++++++++--
>>  include/linux/clk-provider.h |    6 ++++++
>>  2 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index 9955ad7..251e45d 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -219,8 +219,17 @@ static void clk_disable_unused_subtree(struct clk *clk)
>>         if (clk->flags & CLK_IGNORE_UNUSED)
>>                 goto unlock_out;
>>
>> -       if (__clk_is_enabled(clk) && clk->ops->disable)
>> -               clk->ops->disable(clk->hw);
>> +       /*
>> +        * some gate clocks have special needs during the disable-unused
>> +        * sequence.  call .disable_unused if available, otherwise fall
>> +        * back to .disable
>> +        */
>> +       if (__clk_is_enabled(clk)) {
>> +               if (clk->ops->disable_unused)
>> +                       clk->ops->disable_unused(clk->hw);
>> +               else if (clk->ops->disable)
>> +                       clk->ops->disable(clk->hw);
>> +       }
>>
>>  unlock_out:
>>         spin_unlock_irqrestore(&enable_lock, flags);
>> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
>> index 3593a3c..1c94d18 100644
>> --- a/include/linux/clk-provider.h
>> +++ b/include/linux/clk-provider.h
>> @@ -57,6 +57,11 @@ struct clk_hw;
>>   *             This function must not sleep. Optional, if this op is not
>>   *             set then the enable count will be used.
>>   *
>> + * @disable_unused: Disable the clock atomically.  Only called from
>> + *             clk_disable_unused for gate clocks with special needs.
>> + *             Called with enable_lock held.  This function must not
>> + *             sleep.
>> + *
>>   * @recalc_rate        Recalculate the rate of this clock, by querying hardware. The
>>   *             parent rate is an input parameter.  It is up to the caller to
>>   *             ensure that the prepare_mutex is held across this call.
>> @@ -106,6 +111,7 @@ struct clk_ops {
>>         int             (*enable)(struct clk_hw *hw);
>>         void            (*disable)(struct clk_hw *hw);
>>         int             (*is_enabled)(struct clk_hw *hw);
>> +       void            (*disable_unused)(struct clk_hw *hw);
>>         unsigned long   (*recalc_rate)(struct clk_hw *hw,
>>                                         unsigned long parent_rate);
>>         long            (*round_rate)(struct clk_hw *hw, unsigned long,
>> --
>> 1.7.9.5
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> Is there a need for updating the clk documentation around this?
>

I knew I was forgetting something.  The documentation needs a general
cleanup effort and this callback should not go undocumented for long.

> Anyway, you have my:
>
> Acked-by: Ulf Hansson <ulf.hansson at linaro.org>
>

Thanks!

Regards,
Mike

>
> Kind regards
> Ulf Hansson