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SubjectRe: [PATCH 8/9] PM / Domains: Add support for multi PM domains per device to genpd
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On 22/05/18 15:47, Ulf Hansson wrote:
> [...]
>
>>>
>>> +/**
>>> + * genpd_dev_pm_attach_by_id() - Attach a device to one of its PM domain.
>>> + * @dev: Device to attach.
>>> + * @index: The index of the PM domain.
>>> + *
>>> + * Parse device's OF node to find a PM domain specifier at the provided @index.
>>> + * If such is found, allocates a new device and attaches it to retrieved
>>> + * pm_domain ops.
>>> + *
>>> + * Returns the allocated device if successfully attached PM domain, NULL when
>>> + * the device don't need a PM domain or have a single PM domain, else PTR_ERR()
>>> + * in case of failures. Note that if a power-domain exists for the device, but
>>> + * cannot be found or turned on, then return PTR_ERR(-EPROBE_DEFER) to ensure
>>> + * that the device is not probed and to re-try again later.
>>> + */
>>> +struct device *genpd_dev_pm_attach_by_id(struct device *dev,
>>> + unsigned int index)
>>> +{
>>> + struct device *genpd_dev;
>>> + int num_domains;
>>> + int ret;
>>> +
>>> + if (!dev->of_node)
>>> + return NULL;
>>> +
>>> + /* Deal only with devices using multiple PM domains. */
>>> + num_domains = of_count_phandle_with_args(dev->of_node, "power-domains",
>>> + "#power-domain-cells");
>>> + if (num_domains < 2 || index >= num_domains)
>>> + return NULL;
>>> +
>>> + /* Allocate and register device on the genpd bus. */
>>> + genpd_dev = kzalloc(sizeof(*genpd_dev), GFP_KERNEL);
>>> + if (!genpd_dev)
>>> + return ERR_PTR(-ENOMEM);
>>> +
>>> + dev_set_name(genpd_dev, "genpd:%u:%s", index, dev_name(dev));
>>> + genpd_dev->bus = &genpd_bus_type;
>>> + genpd_dev->release = genpd_release_dev;
>>> +
>>> + ret = device_register(genpd_dev);
>>> + if (ret) {
>>> + kfree(genpd_dev);
>>> + return ERR_PTR(ret);
>>> + }
>>> +
>>> + /* Try to attach the device to the PM domain at the specified index. */
>>> + ret = __genpd_dev_pm_attach(genpd_dev, dev->of_node, index);
>>> + if (ret < 1) {
>>> + device_unregister(genpd_dev);
>>> + return ret ? ERR_PTR(ret) : NULL;
>>> + }
>>> +
>>> + pm_runtime_set_active(genpd_dev);
>>> + pm_runtime_enable(genpd_dev);
>>> +
>>> + return genpd_dev;
>>> +}
>>> +EXPORT_SYMBOL_GPL(genpd_dev_pm_attach_by_id);
>>
>> Thanks for sending this. Believe it or not this has still been on my to-do list
>> and so we definitely need a solution for Tegra.
>>
>> Looking at the above it appears that additional power-domains exposed as devices
>> to the client device. So I assume that this means that the drivers for devices
>> with multiple power-domains will need to call RPM APIs for each of these
>> additional power-domains. Is that correct?
>
> They can, but should not!
>
> Instead, the driver shall use device_link_add() and device_link_del(),
> dynamically, depending on what PM domain that their original device
> needs for the current running use case.
>
> In that way, they keep existing runtime PM deployment, operating on
> its original device.

OK, sounds good. Any reason why the linking cannot be handled by the
above API? Is there a use-case where you would not want it linked?

Thanks
Jon

--
nvpublic

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