linux-kernel - Re: [PATCH] phy: core: Add consumer device link support

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Message-ID: <1cd5885d-7db4-59b9-ef2d-e3556f60ca68@st.com>
Date:   Mon, 10 Feb 2020 12:30:22 +0100
From:   Alexandre Torgue <alexandre.torgue@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        youling 257 <youling257@...il.com>
CC:     <yoshihiro.shimoda.uh@...esas.com>, <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <saravanak@...gle.com>
Subject: Re: [PATCH] phy: core: Add consumer device link support

Hi Kishon,

On 2/10/20 9:08 AM, Kishon Vijay Abraham I wrote:
> Hi Alexandre,
> 
> On 07/02/20 12:27 PM, youling 257 wrote:
>> test this diff, dwc3 work for my device, thanks.
>>
>> 2020-02-07 13:16 GMT+08:00, Kishon Vijay Abraham I <kishon@...com>:
>>> Hi,
>>>
>>> On 06/02/20 7:09 PM, youling257 wrote:
>>>> This patch cause "dwc3 dwc3.3.auto: failed to create device link to
>>>> dwc3.3.auto.ulpi" problem.
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=206435
>>>
>>> I'm suspecting there is some sort of reverse dependency with dwc3 ULPI.
>>> Can you try the following diff?
>>>
>>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>>> index 2eb28cc2d2dc..397311dcb116 100644
>>> --- a/drivers/phy/phy-core.c
>>> +++ b/drivers/phy/phy-core.c
>>> @@ -687,7 +687,7 @@ struct phy *phy_get(struct device *dev, const char
>>> *string)
>>>
>>>          get_device(&phy->dev);
>>>
>>> -       link = device_link_add(dev, &phy->dev, DL_FLAG_STATELESS);
>>> +       link = device_link_add(dev, &phy->dev, DL_FLAG_SYNC_STATE_ONLY);
>>>          if (!link) {
>>>                  dev_err(dev, "failed to create device link to %s\n",
>>>                          dev_name(phy->dev.parent));
>>> @@ -802,7 +802,7 @@ struct phy *devm_of_phy_get(struct device *dev,
>>> struct device_node *np,
>>>                  return phy;
>>>          }
>>>
>>> -       link = device_link_add(dev, &phy->dev, DL_FLAG_STATELESS);
>>> +       link = device_link_add(dev, &phy->dev, DL_FLAG_SYNC_STATE_ONLY);
>>>          if (!link) {
>>>                  dev_err(dev, "failed to create device link to %s\n",
>>>                          dev_name(phy->dev.parent));
>>> @@ -851,7 +851,7 @@ struct phy *devm_of_phy_get_by_index(struct device
>>> *dev, struct device_node *np,
>>>          *ptr = phy;
>>>          devres_add(dev, ptr);
>>>
>>> -       link = device_link_add(dev, &phy->dev, DL_FLAG_STATELESS);
>>> +       link = device_link_add(dev, &phy->dev, DL_FLAG_SYNC_STATE_ONLY);
>>>          if (!link) {
>>>                  dev_err(dev, "failed to create device link to %s\n",
>>>                          dev_name(phy->dev.parent));Parent
> 
> Can you check if this doesn't affect the suspend/resume ordering?

With this fix, suspend/resume ordering is broken on my side. What do you 
think to keep the STATELESS flag and to only display a warn if 
"device_link_add" returns an error ? It's not "smart" but it could 
solved our issue.

As a lot of improvements have been recently done on device link topic by 
Saravana, we could check with him what is the way to follow.

Regards
Alex

> 
> Thanks
> Kishon
>