Re: [PATCH v8 07/34] clk: tegra: Support runtime PM and power domain

Dmitry Osipenko
2021-08-18T17:11:13Z

18.08.2021 19:42, Thierry Reding пишет:
> On Wed, Aug 18, 2021 at 06:05:21PM +0300, Dmitry Osipenko wrote:
>> 18.08.2021 17:07, Thierry Reding пишет:
>>> On Tue, Aug 17, 2021 at 04:27:27AM +0300, Dmitry Osipenko wrote:
>>> [...]
>>>> +struct clk *tegra_clk_register(struct clk_hw *hw)
>>>> +{
>>>> + struct platform_device *pdev;
>>>> + struct device *dev = NULL;
>>>> + struct device_node *np;
>>>> + const char *dev_name;
>>>> +
>>>> + np = tegra_clk_get_of_node(hw);
>>>> +
>>>> + if (!of_device_is_available(np))
>>>> + goto put_node;
>>>> +
>>>> + dev_name = kasprintf(GFP_KERNEL, "tegra_clk_%s", hw->init->name);
>>>> + if (!dev_name)
>>>> + goto put_node;
>>>> +
>>>> + pdev = of_platform_device_create(np, dev_name, NULL);
>>>> + if (!pdev) {
>>>> + pr_err("%s: failed to create device for %pOF\n", __func__, np);
>>>> + kfree(dev_name);
>>>> + goto put_node;
>>>> + }
>>>> +
>>>> + dev = &pdev->dev;
>>>> + pm_runtime_enable(dev);
>>>> +put_node:
>>>> + of_node_put(np);
>>>> +
>>>> + return clk_register(dev, hw);
>>>> +}
>>>
>>> This looks wrong. Why do we need struct platform_device objects for each
>>> of these clocks? That's going to be a massive amount of platform devices
>>> and they will completely mess up sysfs.
>>
>> RPM works with a device. It's not a massive amount of devices, it's one
>> device for T20 and four devices for T30.
>
> I'm still not sure I understand why we need to call RPM functions on a
> clock. And even if they are few, it seems wrong to make these platform
> devices.

Before clock is enabled, we need to raise core voltage. After clock is
disabled, the voltage should be dropped. CCF+RPM takes care of handling
this for us.

> Perhaps they can be simple struct device:s instead? Ideally they would
> also be parented to the CAR so that they appear in the right place in
> the sysfs hierarchy.

Could you please clarify what do you mean by 'simple struct device:s'?
These clock devices should be OF devices with a of_node and etc,
otherwise we can't use OPP framework.

We don't have driver for CAR to bind. I guess we could try to add a
'dummy' CAR driver that will create sub-devices for the rpm-clocks, is
this what you're wanting?