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Date:   Thu, 13 Apr 2023 08:29:08 +0200
From:   Herve Codina <herve.codina@bootlin.com>
To:     Vinod Koul <vkoul@kernel.org>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Kishon Vijay Abraham I <kishon@kernel.org>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        linux-phy@lists.infradead.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [RFC PATCH 2/4] phy: Extend API to support 'status' get and
 notification
Message-ID: <20230413082908.4cd44966@bootlin.com>
In-Reply-To: <ZDbg7HMj+x88QXwN@matsya>
References: <20230323103154.264546-1-herve.codina@bootlin.com>
        <20230323103154.264546-3-herve.codina@bootlin.com>
        <ZDbg7HMj+x88QXwN@matsya>
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Hi Vinod,

On Wed, 12 Apr 2023 22:18:44 +0530
Vinod Koul <vkoul@kernel.org> wrote:

> On 23-03-23, 11:31, Herve Codina wrote:
> > The PHY API provides functions to control and pass information from the
> > PHY consumer to the PHY provider.
> > There is no way for the consumer to get direct information from the PHY
> > or be notified by the PHY.
> > 
> > To fill this hole, two API function are provided:
> > 
> > - phy_get_status()
> >   This function can be used to get a "status" from the PHY. It is built
> >   as the same ways as the configure() function. The status information
> >   present in the status retrieved depends on the PHY's phy_mode.
> >   This allows to get a "status" depending on the kind of PHY.  
> 
> what does 'status' mean and communicate to used? How does having this
> help?

'status' can be some information that the PHY can provide to the consumer.
The existing API does not provide a generic way to get some information from
the PHY and 'status' with phy_get_status() provides this generic way.
Its exact meaning depends on the kind of PHY. For the PHY_MODE_BASIC,
introduced in this series, 'status' contains information related to the link
state.
And so, the consumer using a PHY_MODE_BASIC PHY can retreive the link state
getting the 'status' from the PHY.

The patch 3 in this RFC details a consumer usage. An HDLC driver uses a
PHY_MODE_BASIC PHY status to know the PHY link state and calls 
netif_carrier_{on,off}() accordingly.

Best regards,
Hervé

> 
> > 
> > - phy_atomic_notifier_(un)register()
> >   These functions can be used to register/unregister an atomic notifier
> >   block. The event available at this time is the PHY_EVENT_STATUS status
> >   event which purpose is to signal some changes in the status available
> >   using phy_get_status().
> > 
> > An new kind of PHY is added: PHY_MODE_BASIC.
> > This new kind of PHY represents a basic PHY offering a basic status This
> > status contains a link state indication.
> > With the new API, a link state indication can be retrieve using
> > phy_get_status() and link state changes can be notified.
> > 
> > Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> > ---
> >  drivers/phy/phy-core.c        | 88 ++++++++++++++++++++++++++++++++++
> >  include/linux/phy/phy-basic.h | 27 +++++++++++
> >  include/linux/phy/phy.h       | 89 ++++++++++++++++++++++++++++++++++-
> >  3 files changed, 203 insertions(+), 1 deletion(-)
> >  create mode 100644 include/linux/phy/phy-basic.h
> > 
> > diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> > index 9951efc03eaa..c7b568b99dce 100644
> > --- a/drivers/phy/phy-core.c
> > +++ b/drivers/phy/phy-core.c
> > @@ -551,6 +551,94 @@ int phy_validate(struct phy *phy, enum phy_mode mode, int submode,
> >  }
> >  EXPORT_SYMBOL_GPL(phy_validate);
> >  
> > +/**
> > + * phy_get_status() - Gets the phy status
> > + * @phy: the phy returned by phy_get()
> > + * @status: the status to retrieve
> > + *
> > + * Used to get the PHY status. phy_init() must have been called
> > + * on the phy. The status will be retrieved from the current phy mode,
> > + * that can be changed using phy_set_mode().
> > + *
> > + * Return: %0 if successful, a negative error code otherwise
> > + */
> > +int phy_get_status(struct phy *phy, union phy_status *status)
> > +{
> > +	int ret;
> > +
> > +	if (!phy)
> > +		return -EINVAL;
> > +
> > +	if (!phy->ops->get_status)
> > +		return -EOPNOTSUPP;
> > +
> > +	mutex_lock(&phy->mutex);
> > +	ret = phy->ops->get_status(phy, status);
> > +	mutex_unlock(&phy->mutex);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(phy_get_status);
> > +
> > +/**
> > + * phy_atomic_notifier_register() - Registers an atomic notifier
> > + * @phy: the phy returned by phy_get()
> > + * @nb: the notifier block to register
> > + *
> > + * Used to register a notifier block on PHY events. phy_init() must have
> > + * been called on the phy.
> > + * The notifier function given in the notifier_block must not sleep.
> > + * The available PHY events are present in enum phy_events
> > + *
> > + * Return: %0 if successful, a negative error code otherwise
> > + */
> > +int phy_atomic_notifier_register(struct phy *phy, struct notifier_block *nb)
> > +{
> > +	int ret;
> > +
> > +	if (!phy)
> > +		return -EINVAL;
> > +
> > +	if (!phy->ops->atomic_notifier_register ||
> > +	    !phy->ops->atomic_notifier_unregister)
> > +		return -EOPNOTSUPP;
> > +
> > +	mutex_lock(&phy->mutex);
> > +	ret = phy->ops->atomic_notifier_register(phy, nb);
> > +	mutex_unlock(&phy->mutex);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(phy_atomic_notifier_register);
> > +
> > +/**
> > + * phy_atomic_notifier_unregister() - Unregisters an atomic notifier
> > + * @phy: the phy returned by phy_get()
> > + * @nb: the notifier block to unregister
> > + *
> > + * Used to unregister a notifier block. phy_init() must have
> > + * been called on the phy.
> > + *
> > + * Return: %0 if successful, a negative error code otherwise
> > + */
> > +int phy_atomic_notifier_unregister(struct phy *phy, struct notifier_block *nb)
> > +{
> > +	int ret;
> > +
> > +	if (!phy)
> > +		return -EINVAL;
> > +
> > +	if (!phy->ops->atomic_notifier_unregister)
> > +		return -EOPNOTSUPP;
> > +
> > +	mutex_lock(&phy->mutex);
> > +	ret = phy->ops->atomic_notifier_unregister(phy, nb);
> > +	mutex_unlock(&phy->mutex);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(phy_atomic_notifier_unregister);
> > +
> >  /**
> >   * _of_phy_get() - lookup and obtain a reference to a phy by phandle
> >   * @np: device_node for which to get the phy
> > diff --git a/include/linux/phy/phy-basic.h b/include/linux/phy/phy-basic.h
> > new file mode 100644
> > index 000000000000..95668c610c78
> > --- /dev/null
> > +++ b/include/linux/phy/phy-basic.h
> > @@ -0,0 +1,27 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright 2023 CS GROUP France
> > + *
> > + * Author: Herve Codina <herve.codina@bootlin.com>
> > + */
> > +
> > +#ifndef __PHY_BASIC_H_
> > +#define __PHY_BASIC_H_
> > +
> > +#include <linux/types.h>
> > +
> > +/**
> > + * struct phy_status_basic - Basic PHY status
> > + *
> > + * This structure is used to represent the status of a Basic phy.
> > + */
> > +struct phy_status_basic {
> > +	/**
> > +	 * @link_state:
> > +	 *
> > +	 * Link state. true, the link is on, false, the link is off.
> > +	 */
> > +	bool link_is_on;
> > +};
> > +
> > +#endif /* __PHY_DP_H_ */
> > diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
> > index 3a570bc59fc7..40370d41012b 100644
> > --- a/include/linux/phy/phy.h
> > +++ b/include/linux/phy/phy.h
> > @@ -16,6 +16,7 @@
> >  #include <linux/pm_runtime.h>
> >  #include <linux/regulator/consumer.h>
> >  
> > +#include <linux/phy/phy-basic.h>
> >  #include <linux/phy/phy-dp.h>
> >  #include <linux/phy/phy-lvds.h>
> >  #include <linux/phy/phy-mipi-dphy.h>
> > @@ -42,7 +43,8 @@ enum phy_mode {
> >  	PHY_MODE_MIPI_DPHY,
> >  	PHY_MODE_SATA,
> >  	PHY_MODE_LVDS,
> > -	PHY_MODE_DP
> > +	PHY_MODE_DP,
> > +	PHY_MODE_BASIC,
> >  };
> >  
> >  enum phy_media {
> > @@ -67,6 +69,22 @@ union phy_configure_opts {
> >  	struct phy_configure_opts_lvds		lvds;
> >  };
> >  
> > +/**
> > + * union phy_status - Opaque generic phy status
> > + *
> > + * @basic:	Status availbale phys supporting the Basic phy mode.
> > + */
> > +union phy_status {
> > +	struct phy_status_basic		basic;
> > +};
> > +
> > +/**
> > + * phy_event - event available for notification
> > + */
> > +enum phy_event {
> > +	PHY_EVENT_STATUS,	/* Event notified on phy_status changes */
> > +};
> > +
> >  /**
> >   * struct phy_ops - set of function pointers for performing phy operations
> >   * @init: operation to be performed for initializing phy
> > @@ -120,6 +138,45 @@ struct phy_ops {
> >  	 */
> >  	int	(*validate)(struct phy *phy, enum phy_mode mode, int submode,
> >  			    union phy_configure_opts *opts);
> > +
> > +	/**
> > +	 * @get_status:
> > +	 *
> > +	 * Optional.
> > +	 *
> > +	 * Used to get the PHY status. phy_init() must have
> > +	 * been called on the phy.
> > +	 *
> > +	 * Returns: 0 if successful, an negative error code otherwise
> > +	 */
> > +	int	(*get_status)(struct phy *phy, union phy_status *status);
> > +
> > +	/**
> > +	 * @atomic_notifier_register:
> > +	 *
> > +	 * Optional.
> > +	 *
> > +	 * Used to register a notifier block on PHY events. phy_init() must have
> > +	 * been called on the phy.
> > +	 * The notifier function given in the notifier_block must not sleep.
> > +	 * The available PHY events are present in enum phy_events
> > +	 *
> > +	 * Returns: 0 if successful, an negative error code otherwise
> > +	 */
> > +	int	(*atomic_notifier_register)(struct phy *phy, struct notifier_block *nb);
> > +
> > +	/**
> > +	 * @atomic_notifier_unregister:
> > +	 *
> > +	 * Mandatoty if @atomic_notifier_register is set.
> > +	 *
> > +	 * Used to unregister a notifier block on PHY events. phy_init() must have
> > +	 * been called on the phy.
> > +	 *
> > +	 * Returns: 0 if successful, an negative error code otherwise
> > +	 */
> > +	int	(*atomic_notifier_unregister)(struct phy *phy, struct notifier_block *nb);
> > +
> >  	int	(*reset)(struct phy *phy);
> >  	int	(*calibrate)(struct phy *phy);
> >  	void	(*release)(struct phy *phy);
> > @@ -234,6 +291,10 @@ int phy_set_speed(struct phy *phy, int speed);
> >  int phy_configure(struct phy *phy, union phy_configure_opts *opts);
> >  int phy_validate(struct phy *phy, enum phy_mode mode, int submode,
> >  		 union phy_configure_opts *opts);
> > +int phy_get_status(struct phy *phy, union phy_status *status);
> > +int phy_atomic_notifier_register(struct phy *phy, struct notifier_block *nb);
> > +int phy_atomic_notifier_unregister(struct phy *phy, struct notifier_block *nb);
> > +
> >  
> >  static inline enum phy_mode phy_get_mode(struct phy *phy)
> >  {
> > @@ -412,6 +473,32 @@ static inline int phy_validate(struct phy *phy, enum phy_mode mode, int submode,
> >  	return -ENOSYS;
> >  }
> >  
> > +static inline int phy_get_status(struct phy *phy, union phy_status *status)
> > +{
> > +	if (!phy)
> > +		return 0;
> > +
> > +	return -ENOSYS;
> > +}
> > +
> > +static inline int phy_atomic_notifier_register(struct phy *phy,
> > +					       struct notifier_block *nb)
> > +{
> > +	if (!phy)
> > +		return 0;
> > +
> > +	return -ENOSYS;
> > +}
> > +
> > +static inline int phy_atomic_notifier_unregister(struct phy *phy,
> > +						 struct notifier_block *nb)
> > +{
> > +	if (!phy)
> > +		return 0;
> > +
> > +	return -ENOSYS;
> > +}
> > +
> >  static inline int phy_get_bus_width(struct phy *phy)
> >  {
> >  	return -ENOSYS;
> > -- 
> > 2.39.2
> > 
> > 
> > -- 
> > linux-phy mailing list
> > linux-phy@lists.infradead.org
> > https://lists.infradead.org/mailman/listinfo/linux-phy  
>