Hi Wolfram,
On Wed, Dec 16, 2015 at 5:06 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote:
> On Wed, Dec 16, 2015 at 04:55:28PM +0100, Geert Uytterhoeven wrote:
>> On Wed, Dec 16, 2015 at 4:43 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> 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?
>
> Nope, I just finished the sketching phase when Alan's mail came along.
>
>> 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
>> all.
>
> This was another question I had: Is this a bug or a feature :) But if
> you say it is policy, I will count this as "feature" and switch to
> get/put here as well.
It's a feature ;-)
Without using Runtime PM, your driver has to care about clocks and power
domains, which may or may not be present, depending on the SoC.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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