linux-kernel - Re: [PATCH v3 14/16] phy: Add notify

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Message-ID: <082d2ca8-21dc-878f-c668-a76872a7ea92@ti.com>
Date:   Wed, 20 Dec 2017 11:19:10 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Manu Gautam <mgautam@...eaurora.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        "open list:GENERIC PHY FRAMEWORK" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 14/16] phy: Add notify_speed callback

Hi,

On Tuesday 12 December 2017 08:54 PM, Manu Gautam wrote:
> Hi,
> 
> 
> On 12/12/2017 5:13 PM, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Tuesday 21 November 2017 02:53 PM, Manu Gautam wrote:
>>> QCOM USB PHYs can monitor resume/remote-wakeup event in
>>> suspended state. However PHY driver must know current
>>> operational speed of PHY in order to set correct polarity of
>>> wakeup events for detection. E.g. QUSB2 PHY monitors DP/DM
>>> signals depending on speed is LS or FS/HS to detect resume.
>>> Similarly QMP USB3 PHY in SS mode should monitor RX
>>> terminations attach/detach and LFPS events depending on
>>> SSPHY is active or not.

Why not use a notification mechanism instead of adding new APIs in phy-core.
This will only bloat phy-core with APIs for a particular platform.

Thanks
Kishon
>>>
>>> Signed-off-by: Manu Gautam <mgautam@...eaurora.org>
>>> ---
>>>  drivers/phy/phy-core.c  | 30 ++++++++++++++++++++++++++++++
>>>  include/linux/phy/phy.h | 26 ++++++++++++++++++++++++++
>>>  2 files changed, 56 insertions(+)
>>>
>>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>>> index b4964b0..03df2be 100644
>>> --- a/drivers/phy/phy-core.c
>>> +++ b/drivers/phy/phy-core.c
>>> @@ -387,6 +387,36 @@ int phy_calibrate(struct phy *phy)
>>>  }
>>>  EXPORT_SYMBOL_GPL(phy_calibrate);
>>>  
>>> +int phy_notify_speed(struct phy *phy, enum phy_speed speed)
>>> +{
>>> +	int ret;
>>> +
>>> +	if (!phy || !phy->ops->notify_speed)
>>> +		return 0;
>>> +
>>> +	mutex_lock(&phy->mutex);
>>> +	ret = phy->ops->notify_speed(phy, speed);
>>> +	mutex_unlock(&phy->mutex);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(phy_notify_speed);
>>> +
>>> +enum phy_speed phy_get_speed(struct phy *phy)
>>> +{
>>> +	enum phy_speed ret;
>>> +
>>> +	if (!phy || !phy->ops->get_speed)
>>> +		return PHY_SPEED_UNKNOWN;
>>> +
>>> +	mutex_lock(&phy->mutex);
>>> +	ret = phy->ops->get_speed(phy);
>>> +	mutex_unlock(&phy->mutex);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(phy_get_speed);
>> So this is equivalent to set_speed (why notify?) and get_speed. set_speed will
>> most likely be invoked by USB driver? who will invoke get_speed?
> 
> I picked notify_speed as set_speed sounds like driver is going to set/program
> speed related configuration in PHY. Where as the purpose of this function
> is to notify phy_driver of the connection speed of established link.
> USB glue drivers for Qualcomm platforms need to know USB PHYs' speed to
> set correct polarity of wakeup interrupt from hardware in low power state.
>  
> 
>> Thanks
>> Kishon
>