Hi Wolfram,

On Wed, Dec 16, 2015 at 4:43 PM, Wolfram Sang <w...@the-dreams.de> wrote:
> I have another case, may I ask your advice about this, too? When an I2C
> bus is marked in DT as multi-master, then RuntimePM also needs to be
> disabled, because arbitration detection needs to stay awake. I am
> currently implementing this for the i2c-rcar driver:
> -       pm_runtime_enable(dev);
> +       /* No RuntimePM in multi-master to keep arbitration working */
> +       if (!of_get_property(dev->of_node, "multi-master", NULL)) {
> +               pm_runtime_enable(dev);
> +               priv->flags |= ID_P_PM;
> +       }
> +
>         pm_runtime_get_sync(dev);
>         ...
> @@ -664,7 +673,8 @@ static int rcar_i2c_remove(struct platform_device *pdev)
>         struct device *dev = &pdev->dev;
>         i2c_del_adapter(&priv->adap);
> -       pm_runtime_disable(dev);
> +       if (priv->flags & ID_P_PM)
> +               pm_runtime_disable(dev);
>         return 0;
>  }
> Here, I'd tend to keep using enable/disable, although get/put would
> probably also work. What is the rule of thumb using this pattern or the
> other?

Have you actually tried the above?

All our drivers rely on Runtime PM for the power/clock domain handling.
I believe the pm_runtime_get_sync() won't do anything if you haven't enabled
Runtime PM for the device, so the device's module clock won't be enabled at

Hence I think you should add just add additional pm_runtime_get_sync()/
pm_runtime_put() calls in the driver's probe() and remove() methods if
multi-master mode is enabled.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

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