linux-kernel - Re: [PATCH v6 2/2] phy: rockchip-inno-usb2: add a new driver for Rockchip usb2phy

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Message-ID: <3b65b363-72a8-7985-7da1-9045583c90b8@rock-chips.com>
Date:	Mon, 20 Jun 2016 11:32:35 +0800
From:	Frank Wang <frank.wang@...k-chips.com>
To:	Guenter Roeck <groeck@...gle.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Heiko Stübner <heiko@...ech.de>
Cc:	Douglas Anderson <dianders@...omium.org>,
	Guenter Roeck <groeck@...omium.org>, jwerner@...omium.org,
	Kishon Vijay Abraham I <kishon@...com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, Kumar Gala <galak@...eaurora.org>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	Ziyuan Xu <xzy.xu@...k-chips.com>,
	Kever Yang <kever.yang@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>, william.wu@...k-chips.com,
	frank.wang@...k-chips.com
Subject: Re: [PATCH v6 2/2] phy: rockchip-inno-usb2: add a new driver for
 Rockchip usb2phy

Hi Heiko & Guenter,

On 2016/6/20 11:00, Guenter Roeck wrote:
> On Sun, Jun 19, 2016 at 6:27 PM, Frank Wang <frank.wang@...k-chips.com> wrote:
>> Hi Guenter,
>>
>>
>> On 2016/6/17 21:20, Guenter Roeck wrote:
>>> Hi Frank,
>>>
>>> On 06/16/2016 11:43 PM, Frank Wang wrote:
>>>> Hi Guenter,
>>>>
>>>> On 2016/6/17 12:59, Guenter Roeck wrote:
>>>>> On 06/16/2016 07:09 PM, Frank Wang wrote:
>>>>>> The newer SoCs (rk3366, rk3399) take a different usb-phy IP block
>>>>>> than rk3288 and before, and most of phy-related registers are also
>>>>>> different from the past, so a new phy driver is required necessarily.
>>>>>>
>>>>>> Signed-off-by: Frank Wang <frank.wang@...k-chips.com>
>>>>>> Suggested-by: Guenter Roeck <linux@...ck-us.net>
>>>>>> Suggested-by: Doug Anderson <dianders@...omium.org>
>>>>>> Reviewed-by: Heiko Stuebner <heiko@...ech.de>
>>>>>> Tested-by: Heiko Stuebner <heiko@...ech.de>
>>>>>> ---
>>>>>
>>>>> [ ... ]
>>>>>
>>>>>> +
>>>>>> +static int rockchip_usb2phy_resume(struct phy *phy)
>>>>>> +{
>>>>>> +    struct rockchip_usb2phy_port *rport = phy_get_drvdata(phy);
>>>>>> +    struct rockchip_usb2phy *rphy = dev_get_drvdata(phy->dev.parent);
>>>>>> +    int ret;
>>>>>> +
>>>>>> +    dev_dbg(&rport->phy->dev, "port resume\n");
>>>>>> +
>>>>>> +    ret = clk_prepare_enable(rphy->clk480m);
>>>>>> +    if (ret)
>>>>>> +        return ret;
>>>>>> +
>>>>> If suspend can be called multiple times, resume can be called
>>>>> multiple times as well. Doesn't this cause a clock imbalance
>>>>> if you call clk_prepare_enable() multiple times on resume,
>>>>> but clk_disable_unprepare() only once on suspend ?
>>>>>
>>>> Well, what you said is reasonable, How does something like below?
>>>>
>>>> @@ -307,6 +307,9 @@ static int rockchip_usb2phy_resume(struct phy *phy)
>>>>
>>>>           dev_dbg(&rport->phy->dev, "port resume\n");
>>>>
>>>> +       if (!rport->suspended)
>>>> +               return 0;
>>>> +
>>>>           ret = clk_prepare_enable(rphy->clk480m);
>>>>           if (ret)
>>>>                   return ret;
>>>> @@ -327,12 +330,16 @@ static int rockchip_usb2phy_suspend(struct phy
>>>> *phy)
>>>>
>>>>           dev_dbg(&rport->phy->dev, "port suspend\n");
>>>>
>>>> +       if (rport->suspended)
>>>> +               return 0;
>>>> +
>>>>           ret = property_enable(rphy, &rport->port_cfg->phy_sus, true);
>>>>           if (ret)
>>>>                   return ret;
>>>>
>>>>           rport->suspended = true;
>>>>           clk_disable_unprepare(rphy->clk480m);
>>>> +
>>>>           return 0;
>>>>    }
>>>>
>>>> @@ -485,6 +492,7 @@ static int rockchip_usb2phy_host_port_init(struct
>>>> rockchip_usb2phy *rphy,
>>>>
>>>>           rport->port_id = USB2PHY_PORT_HOST;
>>>>           rport->port_cfg = &rphy->phy_cfg->port_cfgs[USB2PHY_PORT_HOST];
>>>> +       rport->suspended = true;
>>>>
>>> Why does it start in suspended mode ? That seems odd.
>>>
>> This is an initialization. Using above design which make 'suspended' as a
>> condition both in *_usb2phy_resume and *_usb2phy_suspend, I believe if it is
>> not initialized as suspended mode, the first resume process will be skipped.
> I had to re-read the entire patch.
>
> Turns out my problem was one of terminology. Using "suspend" and
> "resume" to me suggested the common use of suspend and resume
> functions. That is not the case here. After mentally replacing
> "suspend" with "power_off" and "resume" with "power_on", you are
> right, no problem exists. Sorry for the noise.
>
> Maybe it would be useful to replace "resume" with "power_on" and
> "suspend" with "power_off" in the function and variable names to
> reduce confusion and misunderstandings.
>
> Thanks,
> Guenter

Well, it does have a bits confusion, however, the phy-port always just 
goes to suspend and resume mode (Not power off and power on) in a fact. 
So must it be renamed?

@Heiko Stübner. Hey Heiko, what is your unique perceptions? ;-)


BR.
Frank

>
>> Theoretically, the phy-port in suspended mode make sense when it is at start
>> time, then the upper layer controller will invoke phy_power_on (See
>> phy-core.c), and it further call back *_usb2phy_resume to make phy-port work
>> properly.
>>
>> So could you tell me what make you feeling odd or would you like to give
>> another appropriate way please? :-)
>>
>> BR.
>> Frank
>>
>>
>>>>           mutex_init(&rport->mutex);
>>>>           INIT_DELAYED_WORK(&rport->sm_work, rockchip_usb2phy_sm_work);
>>>>
>>