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

[Leonard Crestez <leonard.crestez@nxp.com>]

On 17.12.2019 02:55, Chanwoo Choi wrote:
> 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.

Maybe I could print a warning if #interconnect-cells is present but 
CONFIG_INTERCONNECT_IMX is off?

An explicit select in Kconfig seems like a pointless limitation but in 
practice it would almost never be useful to build one without the other.

> 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);
>>
>>
> 
>