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. > >pm_runtime_allow() may be omitted but then to make the runtime PM >framework to make the power state transitions this needs to be configured >from the user space --- which I don't think is intended. > >Cc linux-pm, too. > >-- >Regards, > >Sakari Ailus >e-mail: sakari.ailus@xxxxxx ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
