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Message-ID: <bd6fc826-94b9-f539-a37e-820ab49b9d14@linaro.org>
Date:   Mon, 19 Sep 2022 20:29:56 +0300
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Subject: Re: [PATCH v6 3/5] phy: core: Add support for phy power down & power
 up
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To:     Krishna Chaitanya Chundru <quic_krichai@quicinc.com>
Cc:     helgaas@kernel.org, linux-pci@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        mka@chromium.org, quic_vbadigan@quicinc.com,
        quic_hemantk@quicinc.com, quic_nitegupt@quicinc.com,
        quic_skananth@quicinc.com, quic_ramkri@quicinc.com,
        manivannan.sadhasivam@linaro.org, swboyd@chromium.org,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Vinod Koul <vkoul@kernel.org>,
        "open list:GENERIC PHY FRAMEWORK" <linux-phy@lists.infradead.org>
References: <1662713084-8106-1-git-send-email-quic_krichai@quicinc.com>
 <1662713084-8106-4-git-send-email-quic_krichai@quicinc.com>
 <CAA8EJppgaAuEDU44ePOt+ZWK0_rNsXHnE3WOEc9F-n=VE=3aVQ@mail.gmail.com>
 <87138bc9-2fc0-39fb-89c1-d3826e28594e@quicinc.com>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <87138bc9-2fc0-39fb-89c1-d3826e28594e@quicinc.com>
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On 14/09/2022 17:50, Krishna Chaitanya Chundru wrote:
> 
> On 9/9/2022 2:34 PM, Dmitry Baryshkov wrote:
>> On Fri, 9 Sept 2022 at 11:45, Krishna chaitanya chundru
>> <quic_krichai@quicinc.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@quicinc.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?.

What is the difference between power_off() and power_down()?


-- 
With best wishes
Dmitry