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

[Chanwoo Choi <chanwoo@kernel.org>]

2019년 12월 18일 (수) 오후 7:14, Leonard Crestez <leonard.crestez@nxp.com>님이 작성:
>
> 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?

Actually, user might think that if imx-bus.c is enabled
, CONFIG_INTERCONNECT_MIX is enabled.
Because, the dt binding document of imx-bus.c will
contain the property for interconnect.

If device driver support the various feature,
the device driver have to enable all configuration
in order to support the features for user.

>
> 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.

This patch is for the some CONFIG_INTERCONNECT_IMX driver.
I don't understand why is not meaningful to select CONFIG_INTERCONNECT_IMX
in Kconfig?

>
> > 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