On Mon, Oct 9, 2017 at 12:14 PM, Mohandass, Divagar <divagar.mohandass@xxxxxxxxx> wrote: > Hi Tomasz, > >>-----Original Message----- >>From: sakari.ailus@xxxxxx [mailto:sakari.ailus@xxxxxx] >>Sent: Tuesday, October 03, 2017 7:21 PM >>To: Tomasz Figa <tfiga@xxxxxxxxxxxx> >>Cc: Mani, Rajmohan <rajmohan.mani@xxxxxxxxx>; Mohandass, Divagar >><divagar.mohandass@xxxxxxxxx>; robh+dt@xxxxxxxxxx; >>mark.rutland@xxxxxxx; wsa@xxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; >>linux-i2c@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >>mika.westerberg@xxxxxxxxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx >>Subject: Re: [PATCH v6 3/3] eeprom: at24: enable runtime pm support >> >>Hi Tomasz, >> >>On Wed, Sep 20, 2017 at 12:32:22PM +0300, sakari.ailus@xxxxxx wrote: >>> > >> >> @@ -743,11 +770,17 @@ static int at24_probe(struct i2c_client >>> > >> >> *client, const struct i2c_device_id *id) >>> > >> >> >>> > >> >> i2c_set_clientdata(client, at24); >>> > >> >> >>> > >> >> + /* enable runtime pm */ >>> > >> >> + pm_runtime_get_noresume(&client->dev); >>> > >> >> + pm_runtime_set_active(&client->dev); >>> > >> >> + pm_runtime_enable(&client->dev); >>> > >> >>> > >> Do we need this get_noresume/set_active dance? I remember it was >>> > >> for some reason needed for PCI devices, but I don't see why for >>> > >> I2C anything else than just pm_runtime_enable() would be necessary. >>> > > >>> > > You specifically do not need (all) this for PCI devices, but AFAIU >>> > > for I涎 >>> > > devices you do. The runtime PM status of a device is disabled by >>> > > default and the use count is zero, but on ACPI based systems the >>> > > device is still powered on. >>> > >>> > Okay, so _get_noresume() and _set_active() would do the thing for >>> > ACPI indeed, but not sure about other platforms. Perhaps _enable(), >>> > _get_sync() would be more general? >>> >>> What I ended up doing in e.g. the smiapp driver was to explicitly >>> power the device on first and then enable runtime PM. (See >>> drivers/media/i2c/smiapp/smiapp-core.c .) This approach works even if >>> CONFIG_PM is disabled, both on DT and ACPI. >> >>pm_runtime_get_noresume() + pm_runtime_put() can be replaced by a single >>pm_runtime_idle() call (where pm_runtime_put() was). pm_runtime_enable() >>is required to enable runtime PM for a device. > > Verified the change suggested by Sakari. > Let me know I can send a updated patch version with this change. Okay, looks like Sakari confirmed that the driver should work fine without callbacks, so please go ahead. Thanks for patience. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
