Re: [PATCH v6 3/5] phy: core: Add support for phy power down & power up

[Dmitry Baryshkov]

On 14/09/2022 17:50, Krishna Chaitanya Chundru wrote:
> On 9/9/2022 2:34 PM, Dmitry Baryshkov wrote:
> > On Fri, 9 Sept 2022 at 11:45, Krishna chaitanya chundru
> > <quic_krichai@xxxxxxxxxxx> wrote:
> > > Introducing phy power down/up callbacks for allowing to park the
> > > link-state in L1ss without holding any PCIe resources during
> > > system suspend.
> > >
> > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> > > ---
> > >   drivers/phy/phy-core.c  | 30 ++++++++++++++++++++++++++++++
> > >   include/linux/phy/phy.h | 20 ++++++++++++++++++++
> > >   2 files changed, 50 insertions(+)
> > >
> > > diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> > > index d93ddf1..1b0b757 100644
> > > --- a/drivers/phy/phy-core.c
> > > +++ b/drivers/phy/phy-core.c
> > > @@ -441,6 +441,36 @@ int phy_set_speed(struct phy *phy, int speed)
> > >   }
> > >   EXPORT_SYMBOL_GPL(phy_set_speed);
> > >
> > > +int phy_power_down(struct phy *phy)
> > > +{
> > > +       int ret;
> > > +
> > > +       if (!phy || !phy->ops->power_down)
> > > +               return 0;
> > > +
> > > +       mutex_lock(&phy->mutex);
> > > +       ret = phy->ops->power_down(phy);
> > > +       mutex_unlock(&phy->mutex);
> > > +
> > > +       return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(phy_power_down);
> > > +
> > > +int phy_power_up(struct phy *phy)
> > > +{
> > > +       int ret;
> > > +
> > > +       if (!phy || !phy->ops->power_up)
> > > +               return 0;
> > > +
> > > +       mutex_lock(&phy->mutex);
> > > +       ret = phy->ops->power_up(phy);
> > > +       mutex_unlock(&phy->mutex);
> > > +
> > > +       return ret;
> > > +}
> > As it can be seen from the phy_power_off(), the PHY can be a shared
> > resource, with the power_count counting the number of users that
> > requested the PHY to be powered up. By introducing suc calls you break
> > directly into this by allowing a single user to power down the PHY, no
> > matter how many other users have requested the PHY to stay alive.
>
> can we use same power_count in this function also here and restrict the 
> single user to
>
> power down the PHY same like phy_power_off?.

What is the difference between power_off() and power_down()?


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With best wishes
Dmitry