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SubjectRe: [PATCH 02/10] phy: Add configuration interface
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Hi Maxime,

Thank you for the patch.

On Wednesday, 5 September 2018 12:16:33 EEST 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

s/deal/deal with/

> 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.
> + * @opts: New configuration to apply
> + *
> + * 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;

Shouldn't you report an error to the caller ? If a caller expects the PHY to
be configurable, I would assume that silently ignoring the requested
configuration won't work great.

> + 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)
> +{
> + 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);

Is this function allowed to modify opts ? If so, to what extent ? If not, the
pointer should be made const.

> + /**
> + * @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

When should this operation modify the passed parameters, and when should it
return an error ? I understand that your goal is to implement a negotiation
mechanism for the PHY parameters, and to be really useful I think we need to
document it more precisely.

> + */
> + 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);
> static inline enum phy_mode phy_get_mode(struct phy *phy)
> {
> return phy->attrs.mode;

--
Regards,

Laurent Pinchart



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