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

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Message-ID: <ab59a324-d5e1-730a-28a7-01f8af664eb7@rock-chips.com>
Date:	Mon, 20 Jun 2016 09:27:05 +0800
From:	Frank Wang <frank.wang@...k-chips.com>
To:	Guenter Roeck <linux@...ck-us.net>, heiko@...ech.de
Cc:	dianders@...omium.org, groeck@...omium.org, jwerner@...omium.org,
	kishon@...com, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-rockchip@...ts.infradead.org, xzy.xu@...k-chips.com,
	kever.yang@...k-chips.com, 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 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. 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);
>>
>