[PATCH 3/3] ARM: twd_smp: add clock api support

[Colin Cross]

On Thu, Sep 30, 2010 at 7:03 PM, Rob Herring <robherring2 at gmail.com> wrote:
> On 09/30/2010 07:49 PM, Colin Cross wrote:
>>
>> On Thu, Sep 30, 2010 at 3:49 PM, Rob Herring<robherring2 at gmail.com>
>>  wrote:
>>>
>>> From: Rob Herring<rob.herring at smooth-stone.com>
>>>
>>> The private timer freq is currently dynamically detected
>>> using jiffies count to determine the rate. This method adds
>>> a delay to boot-up, so use the clock api instead to get the
>>> clock rate.
>>>
>>> Signed-off-by: Rob Herring<rob.herring at smooth-stone.com>
>>> ---
>>>  arch/arm/include/asm/smp_twd.h |    2 ++
>>>  arch/arm/kernel/smp_twd.c      |    7 +++++++
>>>  2 files changed, 9 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/smp_twd.h
>>> b/arch/arm/include/asm/smp_twd.h
>>> index 634f357..bafad52 100644
>>> --- a/arch/arm/include/asm/smp_twd.h
>>> +++ b/arch/arm/include/asm/smp_twd.h
>>> @@ -19,11 +19,13 @@
>>>  #define TWD_TIMER_CONTROL_IT_ENABLE    (1<<  2)
>>>
>>>  struct clock_event_device;
>>> +struct clk;
>>>
>>>  extern void __iomem *twd_base;
>>>
>>>  void twd_timer_stop(void);
>>>  int twd_timer_ack(void);
>>>  void twd_timer_setup(struct clock_event_device *);
>>> +void twd_timer_init(void __iomem *base, struct clk *clk);
>>>
>>>  #endif
>>> diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
>>> index 35882fb..1a3c959 100644
>>> --- a/arch/arm/kernel/smp_twd.c
>>> +++ b/arch/arm/kernel/smp_twd.c
>>> @@ -17,6 +17,7 @@
>>>  #include<linux/clockchips.h>
>>>  #include<linux/irq.h>
>>>  #include<linux/io.h>
>>> +#include<linux/clk.h>
>>>
>>>  #include<asm/smp_twd.h>
>>>  #include<asm/hardware/gic.h>
>>> @@ -151,6 +152,12 @@ void __cpuinit twd_timer_setup(struct
>>> clock_event_device *clk)
>>>        clockevents_register_device(clk);
>>>  }
>>>
>>> +void __init twd_timer_init(void __iomem *base, struct clk *clk)
>>> +{
>>> +       twd_base = base;
>>> +       twd_timer_rate = clk_get_rate(clk);
>>> +}
>>> +
>>>  #ifdef CONFIG_HOTPLUG_CPU
>>>  /*
>>>  * take a local timer down
>>
>> The local timers run off the PERIPHCLK in the CPU, which is specified
>> as the CPU clock divided by an implementation defined integer>= 2.
>> If you take the divider value as a parameter to twd_timer_init, the
>> clock that is passed in can be the cpu's clock.
>
> That is an implementation detail of the A9. Future designs could be
> completely asynchronous. Using the clock api works either way.

True.  That could still be handled by passing a divider of 1.  For all
current implementations, this api will be used with clock that is a
constant divider of an existing clock.  Taking a divider value would
avoid having to create a new clock that may not be similar to any
other clock in the device.