[RFC/RFT 2/6] clk: qcom: Add runtime support to handle clocks using PM clocks

[Ulf Hansson]

On 24 April 2015 at 12:58, Rajendra Nayak <rnayak at codeaurora.org> wrote:
>
> On 04/24/2015 03:33 PM, Ulf Hansson wrote:
>>
>> On 23 April 2015 at 10:45, Rajendra Nayak <rnayak at codeaurora.org> wrote:
>>>
>>> Add runtime PM support to handle (core and iface) clocks for devices
>>> without a controllable power domain. Once the drivers for these devices
>>> are converted to use runtime PM apis, all clock handling (for core and
>>> iface) from these drivers can then be removed.
>>>
>>> Signed-off-by: Rajendra Nayak <rnayak at codeaurora.org>
>>> ---
>>>   drivers/clk/qcom/gdsc.c | 20 ++++++++++++++++++++
>>>   1 file changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
>>> index 480ebf6..92b0f6d 100644
>>> --- a/drivers/clk/qcom/gdsc.c
>>> +++ b/drivers/clk/qcom/gdsc.c
>>> @@ -15,6 +15,7 @@
>>>   #include <linux/err.h>
>>>   #include <linux/jiffies.h>
>>>   #include <linux/pm_clock.h>
>>> +#include <linux/platform_device.h>
>>>   #include <linux/slab.h>
>>>   #include "gdsc.h"
>>>
>>> @@ -226,3 +227,22 @@ void gdsc_unregister(struct device *dev)
>>>   {
>>>          of_genpd_del_provider(dev->of_node);
>>>   }
>>> +
>>> +static struct dev_pm_domain default_qcom_pm_domain = {
>>> +       .ops = {
>>> +               USE_PM_CLK_RUNTIME_OPS
>>> +               USE_PLATFORM_PM_SLEEP_OPS
>>> +       },
>>> +};
>>> +
>>> +static struct pm_clk_notifier_block qcom_pm_notifier = {
>>> +       .pm_domain      = &default_qcom_pm_domain,
>>> +       .con_ids        = { "core", "iface" },
>>> +};
>>> +
>>> +static int __init qcom_pm_runtime_init(void)
>>> +{
>>> +       pm_clk_add_notifier(&platform_bus_type, &qcom_pm_notifier);
>>> +       return 0;
>>> +}
>>> +core_initcall(qcom_pm_runtime_init);
>>
>>
>> First, I don't follow how this code is related to GDSC.
>
>
> Actually its not. I should probably move it to a pm_runtime.c someplace
> in drivers/soc/qcom maybe.
>
>>
>> Second, I want to see less users of pm_clk_add_notifier() since it's
>> not the proper/long-term way of how to assign PM domain pointers to a
>> device. Instead that shall be done at device registration point. In
>> your case while parsing the DT nodes and adding devices onto to their
>> buses.
>
>
> but these are devices which do not really have a controllable power
> domain, they just have controllable clocks.

That's true. But I don't see an issue why we shouldn't allow to model
this in DT through the existing bindings.

If the DT guys think it's a bad idea, I will anyway think the proper
way to assign PM domains pointers is at device registration point.

>
>>
>> Yes, I understand that it will requires quite some work to adopt to
>> this behaviour - but that how it shall be done.
>>
>> Finally, an important note, you don't need to use PM domains for these
>> devices at all and thus you don't need to fix what I propose. Instead
>> you only have to implement the runtime PM callbacks for each driver
>> and manage the clocks from there. That is probably also a easier
>> solution.
>
>
> But that would mean I repeat the same code in all drivers to do a
> clk_get/prepare/enable/disable/unprepare of the same "core" and "iface"
> clocks. I thought we have clock_ops.c just to avoid that (atleast up
> until we have a better way of doing it)
> And there are atleast a few architecture which have used it to avoid the
> duplication across all drivers (omap1/davinci/sh/keystone)

Yes, the "duplications" are unavoidable if you decide to follow my suggestion.

On the other hand your drivers will be more "standalone" and not
depending on that you have a PM domain attached to the device to
actually work. In some cases that might even be useful, when you have
a cross SOC driver used in various configurations.

Kind regards
Uffe