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Subject: Re: [PATCH 02/10] phy: Add configuration interface
To:     Maxime Ripard <maxime.ripard@bootlin.com>,
        Boris Brezillon <boris.brezillon@bootlin.com>
CC:     Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        <linux-media@vger.kernel.org>,
        Archit Taneja <architt@codeaurora.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Chen-Yu Tsai <wens@csie.org>, <linux-kernel@vger.kernel.org>,
        <dri-devel@lists.freedesktop.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Krzysztof Witos <kwitos@cadence.com>,
        Rafal Ciepiela <rafalc@cadence.com>
References: <cover.ee6158898d563fcc01d45c9652501180bccff0f0.1536138624.git-series.maxime.ripard@bootlin.com>
 <a739a2d623c3e60373a73e1ec206c2aa35c4a742.1536138624.git-series.maxime.ripard@bootlin.com>
From:   Kishon Vijay Abraham I <kishon@ti.com>
Message-ID: <1ed01c1f-76d5-fa96-572b-9bfd269ad11b@ti.com>
Date:   Thu, 6 Sep 2018 14:57:58 +0530
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Hi,

On Wednesday 05 September 2018 02:46 PM, Maxime Ripard wrote:
> The phy framework is only allowing to configure the power state of the PHY
> using the init and power_on hooks, and their power_off and exit
> counterparts.
> 
> While it works for most, simple, PHYs supported so far, some more advanced
> PHYs need some configuration depending on runtime parameters. These PHYs
> have been supported by a number of means already, often by using ad-hoc
> drivers in their consumer drivers.
> 
> That doesn't work too well however, when a consumer device needs to deal
> multiple PHYs, or when multiple consumers need to deal with the same PHY (a
> DSI driver and a CSI driver for example).
> 
> So we'll add a new interface, through two funtions, phy_validate and
> phy_configure. The first one will allow to check that a current
> configuration, for a given mode, is applicable. It will also allow the PHY
> driver to tune the settings given as parameters as it sees fit.
> 
> phy_configure will actually apply that configuration in the phy itself.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
>  drivers/phy/phy-core.c  | 62 ++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/phy/phy.h | 42 ++++++++++++++++++++++++++++-
>  2 files changed, 104 insertions(+)
> 
> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> index 35fd38c5a4a1..6eaf655e370f 100644
> --- a/drivers/phy/phy-core.c
> +++ b/drivers/phy/phy-core.c
> @@ -408,6 +408,68 @@ int phy_calibrate(struct phy *phy)
>  EXPORT_SYMBOL_GPL(phy_calibrate);
>  
>  /**
> + * phy_configure() - Changes the phy parameters
> + * @phy: the phy returned by phy_get()
> + * @mode: phy_mode the configuration is applicable to.

mode should be used if the same PHY can be configured in multiple modes. But
with phy_set_mode() and phy_calibrate() we could achieve the same.
> + * @opts: New configuration to apply

Should these configuration come from the consumer driver? Can't the helper
functions be directly invoked by the PHY driver for the configuration.
> + *
> + * Used to change the PHY parameters. phy_init() must have
> + * been called on the phy.
> + *
> + * Returns: 0 if successful, an negative error code otherwise
> + */
> +int phy_configure(struct phy *phy, enum phy_mode mode,
> +		  union phy_configure_opts *opts)
> +{> +	int ret;
> +
> +	if (!phy)
> +		return -EINVAL;
> +
> +	if (!phy->ops->configure)
> +		return 0;
> +
> +	mutex_lock(&phy->mutex);
> +	ret = phy->ops->configure(phy, mode, opts);
> +	mutex_unlock(&phy->mutex);
> +
> +	return ret;
> +}
> +
> +/**
> + * phy_validate() - Checks the phy parameters
> + * @phy: the phy returned by phy_get()
> + * @mode: phy_mode the configuration is applicable to.
> + * @opts: Configuration to check
> + *
> + * Used to check that the current set of parameters can be handled by
> + * the phy. Implementations are free to tune the parameters passed as
> + * arguments if needed by some implementation detail or
> + * constraints. It will not change any actual configuration of the
> + * PHY, so calling it as many times as deemed fit will have no side
> + * effect.
> + *
> + * Returns: 0 if successful, an negative error code otherwise
> + */
> +int phy_validate(struct phy *phy, enum phy_mode mode,
> +		  union phy_configure_opts *opts)

IIUC the consumer driver will pass configuration options (or PHY parameters)
which will be validated by the PHY driver and in some cases the PHY driver can
modify the configuration options? And these modified configuration options will
again be given to phy_configure?

Looks like it's a round about way of doing the same thing.


> +{
> +	int ret;
> +
> +	if (!phy)
> +		return -EINVAL;
> +
> +	if (!phy->ops->validate)
> +		return 0;
> +
> +	mutex_lock(&phy->mutex);
> +	ret = phy->ops->validate(phy, mode, opts);
> +	mutex_unlock(&phy->mutex);
> +
> +	return ret;
> +}
> +
> +/**
>   * _of_phy_get() - lookup and obtain a reference to a phy by phandle
>   * @np: device_node for which to get the phy
>   * @index: the index of the phy
> diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
> index 9cba7fe16c23..3cc315dcfcd0 100644
> --- a/include/linux/phy/phy.h
> +++ b/include/linux/phy/phy.h
> @@ -44,6 +44,12 @@ enum phy_mode {
>  };
>  
>  /**
> + * union phy_configure_opts - Opaque generic phy configuration
> + */
> +union phy_configure_opts {
> +};
> +
> +/**
>   * struct phy_ops - set of function pointers for performing phy operations
>   * @init: operation to be performed for initializing phy
>   * @exit: operation to be performed while exiting
> @@ -60,6 +66,38 @@ struct phy_ops {
>  	int	(*power_on)(struct phy *phy);
>  	int	(*power_off)(struct phy *phy);
>  	int	(*set_mode)(struct phy *phy, enum phy_mode mode);
> +
> +	/**
> +	 * @configure:
> +	 *
> +	 * Optional.
> +	 *
> +	 * Used to change the PHY parameters. phy_init() must have
> +	 * been called on the phy.
> +	 *
> +	 * Returns: 0 if successful, an negative error code otherwise
> +	 */
> +	int	(*configure)(struct phy *phy, enum phy_mode mode,
> +			     union phy_configure_opts *opts);
> +
> +	/**
> +	 * @validate:
> +	 *
> +	 * Optional.
> +	 *
> +	 * Used to check that the current set of parameters can be
> +	 * handled by the phy. Implementations are free to tune the
> +	 * parameters passed as arguments if needed by some
> +	 * implementation detail or constraints. It must not change
> +	 * any actual configuration of the PHY, so calling it as many
> +	 * times as deemed fit by the consumer must have no side
> +	 * effect.
> +	 *
> +	 * Returns: 0 if the configuration can be applied, an negative
> +	 * error code otherwise
> +	 */
> +	int	(*validate)(struct phy *phy, enum phy_mode mode,
> +			    union phy_configure_opts *opts);
>  	int	(*reset)(struct phy *phy);
>  	int	(*calibrate)(struct phy *phy);
>  	struct module *owner;
> @@ -164,6 +202,10 @@ int phy_exit(struct phy *phy);
>  int phy_power_on(struct phy *phy);
>  int phy_power_off(struct phy *phy);
>  int phy_set_mode(struct phy *phy, enum phy_mode mode);
> +int phy_configure(struct phy *phy, enum phy_mode mode,
> +		  union phy_configure_opts *opts);
> +int phy_validate(struct phy *phy, enum phy_mode mode,
> +		 union phy_configure_opts *opts);

Stub function when CONFIG_GENERIC_PHY is not set is also required.

Thanks
Kishon