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

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Date:   Fri, 9 Sep 2022 12:04:53 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     helgaas@...nel.org, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mka@...omium.org, quic_vbadigan@...cinc.com,
        quic_hemantk@...cinc.com, quic_nitegupt@...cinc.com,
        quic_skananth@...cinc.com, quic_ramkri@...cinc.com,
        manivannan.sadhasivam@...aro.org, swboyd@...omium.org,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        "open list:GENERIC PHY FRAMEWORK" <linux-phy@...ts.infradead.org>
Subject: Re: [PATCH v6 3/5] phy: core: Add support for phy power down & power up

On Fri, 9 Sept 2022 at 11:45, Krishna chaitanya chundru
<quic_krichai@...cinc.com> 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@...cinc.com>
> ---
>  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.

> +EXPORT_SYMBOL_GPL(phy_power_up);
> +
>  int phy_reset(struct phy *phy)
>  {
>         int ret;
> diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
> index b141375..3a45f4d 100644
> --- a/include/linux/phy/phy.h
> +++ b/include/linux/phy/phy.h
> @@ -76,6 +76,8 @@ union phy_configure_opts {
>   * @set_mode: set the mode of the phy
>   * @set_media: set the media type of the phy (optional)
>   * @set_speed: set the speed of the phy (optional)
> + * @power_down: parking the phy in power down state
> + * @power_up: pulling back the phy from power down
>   * @reset: resetting the phy
>   * @calibrate: calibrate the phy
>   * @release: ops to be performed while the consumer relinquishes the PHY
> @@ -89,6 +91,8 @@ struct phy_ops {
>         int     (*set_mode)(struct phy *phy, enum phy_mode mode, int submode);
>         int     (*set_media)(struct phy *phy, enum phy_media media);
>         int     (*set_speed)(struct phy *phy, int speed);
> +       int     (*power_down)(struct phy *phy);
> +       int     (*power_up)(struct phy *phy);
>
>         /**
>          * @configure:
> @@ -226,6 +230,8 @@ int phy_init(struct phy *phy);
>  int phy_exit(struct phy *phy);
>  int phy_power_on(struct phy *phy);
>  int phy_power_off(struct phy *phy);
> +int phy_power_down(struct phy *phy);
> +int phy_power_up(struct phy *phy);
>  int phy_set_mode_ext(struct phy *phy, enum phy_mode mode, int submode);
>  #define phy_set_mode(phy, mode) \
>         phy_set_mode_ext(phy, mode, 0)
> @@ -349,6 +355,20 @@ static inline int phy_power_off(struct phy *phy)
>         return -ENOSYS;
>  }
>
> +static inline int phy_power_down(struct phy *phy)
> +{
> +       if (!phy)
> +               return 0;
> +       return -ENOSYS;
> +}
> +
> +static inline int phy_power_up(struct phy *phy)
> +{
> +       if (!phy)
> +               return 0;
> +       return -ENOSYS;
> +}
> +
>  static inline int phy_set_mode_ext(struct phy *phy, enum phy_mode mode,
>                                    int submode)
>  {
> --
> 2.7.4
>


-- 
With best wishes
Dmitry