Re: [PATCH RFC v6 3/9] PM / devfreq: imx: Register interconnect device

[Chanwoo Choi <cw00.choi@samsung.com>]

On 12/17/19 12:00 AM, Leonard Crestez wrote:
> On 13.12.2019 06:22, Chanwoo Choi wrote:
>> Hi,
>>
>> On 11/15/19 5:09 AM, Leonard Crestez wrote:
>>> There is no single device which can represent the imx interconnect.
>>> Instead of adding a virtual one just make the main &noc act as the
>>> global interconnect provider.
>>>
>>> The imx interconnect provider driver will scale the NOC and DDRC based
>>> on bandwidth request. More scalable nodes can be added in the future,
>>> for example for audio/display/vpu/gpu NICs.
>>>
>>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>>> ---
>>>   drivers/devfreq/imx-devfreq.c | 37 +++++++++++++++++++++++++++++++++++
>>>   1 file changed, 37 insertions(+)
>>>
>>> diff --git a/drivers/devfreq/imx-devfreq.c b/drivers/devfreq/imx-devfreq.c
>>> index 620b344e87aa..585d340c0f6e 100644
>>> --- a/drivers/devfreq/imx-devfreq.c
>>> +++ b/drivers/devfreq/imx-devfreq.c
>>> @@ -15,10 +15,11 @@
>>>   struct imx_devfreq {
>>>   	struct devfreq_dev_profile profile;
>>>   	struct devfreq *devfreq;
>>>   	struct clk *clk;
>>>   	struct devfreq_passive_data passive_data;
>>> +	struct platform_device *icc_pdev;
>>>   };
>>>   
>>>   static int imx_devfreq_target(struct device *dev,
>>>   			      unsigned long *freq, u32 flags)
>>>   {
>>> @@ -60,11 +61,40 @@ static int imx_devfreq_get_dev_status(struct device *dev,
>>>   	return 0;
>>>   }
>>>   
>>>   static void imx_devfreq_exit(struct device *dev)
>>>   {
>>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>>> +
>>>   	dev_pm_opp_of_remove_table(dev);
>>> +	platform_device_unregister(priv->icc_pdev);
>>> +}
>>> +
>>> +/* imx_devfreq_init_icc() - register matching icc provider if required */
>>> +static int imx_devfreq_init_icc(struct device *dev)
>>> +{
>>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>>> +	const char *icc_driver_name;
>>> +
>>> +	if (!IS_ENABLED(CONFIG_INTERCONNECT_IMX))
>>> +		return 0;
>>
>> It is not proper to check the enable state of CONFIG_INTERCONNECT_IMX configuration
>> on device driver. Why don't you add the 'select CONFIG_INTERCONNECT_IMX' on Kconfig?
> 
> Because it's optional.
> 
> You can disable interconnect support and just tweak frequencies using 
> the devfreq sysfs API. But indeed would only really be useful for debugging.

Even if it's optional, I don't prefer to use 'IS_ENABLED' macro.

Generally, add or delete the property or value at DT file
to either enable or disable the some feature provided by device driver
instead of checking the configuration.

If user adds the property/value related to interconnect
and imx-bus.c configuration is enabled, the behavior
related to interconnect on imx-bus.c doesn't work. It make some confusion.

The imx-bus.c have to add the 'select CONFIG_INTERCONNECT_IMX'
and hand over the right which use the interconnect feature or not, to user.

If there are any requirement to add the additional property
to check whether interconnect feature will be used or not,
you can add the extra property. But, I think that it is enough
to check the '#interconnect-cells'.

In result, I think that it is right to decide the usage of feature
of device driver by user on Devicetree.

> 
>>> +	if (!of_get_property(dev->of_node, "#interconnect-cells", 0))
>>> +		return 0;
>>> +
>>> +	icc_driver_name = of_device_get_match_data(dev);
>>> +	if (!icc_driver_name)
>>> +		return 0;
>>> +
>>> +	priv->icc_pdev = platform_device_register_data(
>>> +			dev, icc_driver_name, 0, NULL, 0);
>>> +	if (IS_ERR(priv->icc_pdev)) {
>>> +		dev_err(dev, "failed to register icc provider %s: %ld\n",
>>> +				icc_driver_name, PTR_ERR(priv->devfreq));
>>> +		return PTR_ERR(priv->devfreq);
>>> +	}
>>> +
>>> +	return 0;
>>>   }
>>>   
>>>   static int imx_devfreq_probe(struct platform_device *pdev)
>>>   {
>>>   	struct device *dev = &pdev->dev;
>>> @@ -120,18 +150,25 @@ static int imx_devfreq_probe(struct platform_device *pdev)
>>>   		ret = PTR_ERR(priv->devfreq);
>>>   		dev_err(dev, "failed to add devfreq device: %d\n", ret);
>>>   		goto err;
>>>   	}
>>>   
>>> +	ret = imx_devfreq_init_icc(dev);
>>> +	if (ret)
>>> +		goto err;
>>> +
>>>   	return 0;
>>>   
>>>   err:
>>>   	dev_pm_opp_of_remove_table(dev);
>>>   	return ret;
>>>   }
>>>   
>>>   static const struct of_device_id imx_devfreq_of_match[] = {
>>> +	{ .compatible = "fsl,imx8mq-noc", .data = "imx8mq-interconnect", },
>>> +	{ .compatible = "fsl,imx8mm-noc", .data = "imx8mm-interconnect", },
>>> +	{ .compatible = "fsl,imx8mn-noc", .data = "imx8mn-interconnect", },
>>>   	{ .compatible = "fsl,imx8m-noc", },
>>>   	{ .compatible = "fsl,imx8m-nic", },
>>>   	{ /* sentinel */ },
>>>   };
>>>   MODULE_DEVICE_TABLE(of, imx_devfreq_of_match);
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics