linux-kernel - Re: [PATCH v7 3/4] usb: dwc2: assert phy reset when waking up in rk3288 platform

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Message-ID: <1ac13d9d-39c4-c110-d5ab-2dee30c0b4aa@synopsys.com>
Date:   Tue, 6 Sep 2016 19:02:20 -0700
From:   John Youn <John.Youn@...opsys.com>
To:     Ayaka <ayaka@...lik.info>, John Youn <John.Youn@...opsys.com>
CC:     Kishon Vijay Abraham I <kishon@...com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "heiko@...ech.de" <heiko@...ech.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "randy.li@...k-chips.com" <randy.li@...k-chips.com>
Subject: Re: [PATCH v7 3/4] usb: dwc2: assert phy reset when waking up in
 rk3288 platform

On 9/6/2016 6:19 PM, Ayaka wrote:
> 
> 
> 從我的 iPad 傳送
> 
>> John Youn <John.Youn@...opsys.com> 於 2016年9月7日 上午2:54 寫道：
>>
>>> On 9/5/2016 10:15 PM, Kishon Vijay Abraham I wrote:
>>> Hi,
>>>
>>>> On Sunday 04 September 2016 03:25 AM, Randy Li wrote:
>>>> On the rk3288 USB host-only port (the one that's not the OTG-enabled
>>>> port) the PHY can get into a bad state when a wakeup is asserted (not
>>>> just a wakeup from full system suspend but also a wakeup from
>>>> autosuspend).
>>>>
>>>> We can get the PHY out of its bad state by asserting its "port reset",
>>>> but unfortunately that seems to assert a reset onto the USB bus so it
>>>> could confuse things if we don't actually deenumerate / reenumerate the
>>>> device.
>>>>
>>>> We can also get the PHY out of its bad state by fully resetting it using
>>>> the reset from the CRU (clock reset unit) in chip, which does a more full
>>>> reset.  The CRU-based reset appears to actually cause devices on the bus
>>>> to be removed and reinserted, which fixes the problem (albeit in a hacky
>>>> way).
>>>>
>>>> It's unfortunate that we need to do a full re-enumeration of devices at
>>>> wakeup time, but this is better than alternative of letting the bus get
>>>> wedged.
>>>>
>>>> Signed-off-by: Randy Li <ayaka@...lik.info>
>>>> ---
>>>> drivers/usb/dwc2/core_intr.c | 12 ++++++++++++
>>>> 1 file changed, 12 insertions(+)
>>>>
>>>> diff --git a/drivers/usb/dwc2/core_intr.c b/drivers/usb/dwc2/core_intr.c
>>>> index d85c5c9..08485b7 100644
>>>> --- a/drivers/usb/dwc2/core_intr.c
>>>> +++ b/drivers/usb/dwc2/core_intr.c
>>>> @@ -345,6 +345,7 @@ static void dwc2_handle_session_req_intr(struct dwc2_hsotg *hsotg)
>>>> static void dwc2_handle_wakeup_detected_intr(struct dwc2_hsotg *hsotg)
>>>> {
>>>>    int ret;
>>>> +    struct device_node *np = hsotg->dev->of_node;
>>>>
>>>>    /* Clear interrupt */
>>>>    dwc2_writel(GINTSTS_WKUPINT, hsotg->regs + GINTSTS);
>>>> @@ -379,6 +380,17 @@ static void dwc2_handle_wakeup_detected_intr(struct dwc2_hsotg *hsotg)
>>>>            /* Restart the Phy Clock */
>>>>            pcgcctl &= ~PCGCTL_STOPPCLK;
>>>>            dwc2_writel(pcgcctl, hsotg->regs + PCGCTL);
>>>> +
>>>> +            /*
>>>> +             * It is a quirk in Rockchip RK3288, causing by
>>>> +             * a hardware bug. This will propagate out and
>>>> +             * eventually we'll re-enumerate the device. 
>>>> +             * Not great but the best we can do 
>>>> +             */
>>>> +            if (of_device_is_compatible(np, "rockchip,rk3288-usb")
>>>> +                    && (NULL != hsotg->phy->ops->reset))
>>>> +                hsotg->phy->ops->reset(hsotg->phy);
>>>
>>> never call the phy ops directly from the controller driver. It has to be
>>> protected as well.
>>
>> It looks like we should be calling an API function instead, correct?
>>
> Could you give me a example for the wrapper of phy ops?

Check these files:
* include/linux/phy/phy.h
* drivers/phy/phy-core.c

Search for "phy_set_mode".

I'm thinking there should be a "phy_reset" API function which calls
the phy->ops->reset in a similar manner. With the same runtime checks
and stub function if CONFIG_GENERIC_PHY is not enabled.

Regards,
John