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

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Message-ID: <87138bc9-2fc0-39fb-89c1-d3826e28594e@quicinc.com>
Date:   Wed, 14 Sep 2022 20:20:14 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 9/9/2022 2:34 PM, Dmitry Baryshkov wrote:
> 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.

can we use same power_count in this function also here and restrict the 
single user to

power down the PHY same like phy_power_off?.

>> +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
>>
>