On 4 January 2011 09:58, Amit Kucheria <amit.kuche...@linaro.org> wrote:
> CC'ing linaro-dev
>
> On Tue, Jan 4, 2011 at 1:18 PM, Yong Shen <yong.s...@linaro.org> wrote:
>> hi there,
>>
>> In last weekly meeting, we talked about the real time display of clock
>> information in powerdebug.
>
> What do you mean by real-time display?
>
> powerdebug will only refresh it's information every 'n' seconds. At
> that point, the 'show' function for the sysfs rate entry should call
> get_rate() for the clock.
>
>> Actually, this feature can be easily supported. if you found some
>> clocks' information stay unchanged after your drivers change clock
>> setting, it may be caused by the wrong way of clock information
>> exposing.
>>
>> In the last several weeks, Jeremy and I reviewed the clock debug code
>> based on common clock struct. In this code, I used below code to
>> expose clock information:
>>
ok for the clock rate but how do you manage a change of the clock's
parent ? I mean , if a driver sets a new parent of a clock with
clk_set_parent, we should also update the debugfs clock tree in order
to reflect this modification. I'm not sure that we need to update the
debugfs clock tree in a real time manner but we should be able to
force a refresh of the clock debugfs.
>>
>> +static int clk_debug_rate_get(void *data, u64 *val)
>> +{
>> + struct clk *clk = data;
>> +
>> + *val = (u64)clk_get_rate(clk);
>> + return 0;
>> +}
>> +DEFINE_SIMPLE_ATTRIBUTE(clk_debug_rate_fops, clk_debug_rate_get, NULL,
>> + "%llu\n");
>> +
>> .....
>> + d = debugfs_create_file("rate", S_IRUGO, clk->dentry, (void *)clk,
>> + &clk_debug_rate_fops);
>>
>> Therefore, whenever the clock information is accessed, it can reflect
>> the truth, since it calls clk interface like clk_get_rate() to get the
>> right value.
>
> Why is it called clk_debug_rate_get()? Is there not a standard
> clk_rate_get() that we can use?
>
>> Previously, some of you might use a variable to store clock
>> information like rate or count, and expose these variable to sysfs,
>> which is why they are not updated when the real clock information is
>> changing.
>
> Right, storing in variables will give wrong results if you're in the
> middle of a rate refresh.
>
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