linux-kernel - RE: [PATCH v4 1/2] phy: core: add phy_property

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Date:   Fri, 22 Nov 2019 08:12:57 +0530
From:   "Pankaj Dubey" <pankaj.dubey@...sung.com>
To:     "'Andrew Murray'" <andrew.murray@....com>,
        "'Anvesh Salveru'" <anvesh.s@...sung.com>
Cc:     <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>,
        <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <kishon@...com>, <robh+dt@...nel.org>, <mark.rutland@....com>
Subject: RE: [PATCH v4 1/2] phy: core: add phy_property_present method



> -----Original Message-----
> From: Andrew Murray <andrew.murray@....com>
> Sent: Thursday, November 21, 2019 9:39 PM
> To: Anvesh Salveru <anvesh.s@...sung.com>
> Cc: linux-kernel@...r.kernel.org; linux-pci@...r.kernel.org;
> jingoohan1@...il.com; gustavo.pimentel@...opsys.com;
> pankaj.dubey@...sung.com; lorenzo.pieralisi@....com;
> bhelgaas@...gle.com; kishon@...com; robh+dt@...nel.org;
> mark.rutland@....com
> Subject: Re: [PATCH v4 1/2] phy: core: add phy_property_present method
> 
> On Thu, Nov 21, 2019 at 08:50:07AM +0530, Anvesh Salveru wrote:
> > In some platforms, we need information of phy properties in the
> > controller drivers. This patch adds a new phy_property_present()
> > method which can be used to check if some property exists in PHY or
> > not.
> >
> > In case of DesignWare PCIe controller, we need to write into
> > controller register to specify about ZRX-DC compliance property of the
> > PHY, which reduces the power consumption during lower power states.
> >
> > Signed-off-by: Anvesh Salveru <anvesh.s@...sung.com>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> > ---
> >  drivers/phy/phy-core.c  | 26 ++++++++++++++++++++++++++
> > include/linux/phy/phy.h |  8 ++++++++
> >  2 files changed, 34 insertions(+)
> >
> > diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c index
> > b04f4fe..0a62eca 100644
> > --- a/drivers/phy/phy-core.c
> > +++ b/drivers/phy/phy-core.c
> > @@ -420,6 +420,32 @@ int phy_calibrate(struct phy *phy)
> > EXPORT_SYMBOL_GPL(phy_calibrate);
> >
> >  /**
> > + * phy_property_present() - checks if the property is present in PHY
> > + * @phy: the phy returned by phy_get()
> > + * @property: name of the property to check
> > + *
> > + * Used to check if the given property is present in PHY. PHY drivers
> > + * can implement this callback function to expose PHY properties to
> > + * controller drivers.
> > + *
> > + * Returns: true if property exists, false otherwise  */ bool
> > +phy_property_present(struct phy *phy, const char *property) {
> > +	bool ret;
> > +
> > +	if (!phy || !phy->ops->property_present)
> > +		return false;
> > +
> > +	mutex_lock(&phy->mutex);
> > +	ret = phy->ops->property_present(phy, property);
> 
> I don't understand why it is necessary to require every phy driver to
implement
> this. Why can't the phy-core driver look up the device node of the given
phy?
> 

No specific reason.

We just went ahead and implemented this similar to other API in phy-core.c
file where it redirects call to platform specific phy driver. As  you
pointed out in this case, it makes sense to keep it in phy-core driver
itself, as platform specific phy driver is not going to do anything which is
really dependent on the PHY. 
We will wait for further review comments on this patch, and then will take
up your suggestion in next patchset.

Thanks for review.
Pankaj Dubey
> Thanks,
> 
> Andrew Murray
> 
> > +	mutex_unlock(&phy->mutex);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(phy_property_present);
> > +
> > +/**
> >   * phy_configure() - Changes the phy parameters
> >   * @phy: the phy returned by phy_get()
> >   * @opts: New configuration to apply
> > diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h index
> > 15032f14..3dd8f3c 100644
> > --- a/include/linux/phy/phy.h
> > +++ b/include/linux/phy/phy.h
> > @@ -61,6 +61,7 @@ union phy_configure_opts {
> >   * @reset: resetting the phy
> >   * @calibrate: calibrate the phy
> >   * @release: ops to be performed while the consumer relinquishes the
> > PHY
> > + * @property_present: check if some property is present in PHY
> >   * @owner: the module owner containing the ops
> >   */
> >  struct phy_ops {
> > @@ -103,6 +104,7 @@ struct phy_ops {
> >  	int	(*reset)(struct phy *phy);
> >  	int	(*calibrate)(struct phy *phy);
> >  	void	(*release)(struct phy *phy);
> > +	bool	(*property_present)(struct phy *phy, const char *property);
> >  	struct module *owner;
> >  };
> >
> > @@ -217,6 +219,7 @@ static inline enum phy_mode phy_get_mode(struct
> > phy *phy)  }  int phy_reset(struct phy *phy);  int
> > phy_calibrate(struct phy *phy);
> > +bool phy_property_present(struct phy *phy, const char *property);
> >  static inline int phy_get_bus_width(struct phy *phy)  {
> >  	return phy->attrs.bus_width;
> > @@ -354,6 +357,11 @@ static inline int phy_calibrate(struct phy *phy)
> >  	return -ENOSYS;
> >  }
> >
> > +static inline bool phy_property_present(struct phy *phy, const char
> > +*property) {
> > +	return false;
> > +}
> > +
> >  static inline int phy_configure(struct phy *phy,
> >  				union phy_configure_opts *opts)
> >  {
> > --
> > 2.7.4
> >