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

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Date:   Wed, 24 Aug 2016 16:54:16 +0800
From:   Randy Li <randy.li@...k-chips.com>
To:     John Youn <John.Youn@...opsys.com>, Randy Li <ayaka@...lik.info>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Cc:     "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>,
        "eddie.cai@...k-chips.com" <eddie.cai@...k-chips.com>,
        "kishon@...com" <kishon@...com>
Subject: Re: [RESEND PATCH 3/4] usb: dwc2: assert phy reset when waking up in
 rk3288 platform


On 08/24/2016 04:46 AM, John Youn wrote:
> On 8/21/2016 12:32 PM, 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 | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/usb/dwc2/core_intr.c b/drivers/usb/dwc2/core_intr.c
>> index d85c5c9..f57c48a 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 +380,16 @@ 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
>
> Remove the trailing whitespaces in this comment.
>
> Run scripts/checkpatch.pl to catch these.
I see.
>
>> +			 */
>> +			if (of_device_is_compatible(np, "rockchip,rk3288-usb"))
>> +				hsotg->phy->ops->reset(hsotg->phy);
>> +
>
> You should probably check for NULL before calling the reset()
> callback.
Sure.
>
> Also, I'd rather see a generic quirk property that you set for your
> platform.
>
> Something like "phy_reset_on_wakeup_quirk".
But Rob Herring want me to implied by the SoC specific compatible 
string. I agree with him. It is certainly bug in RK3288 platform.
It is no found no the other platform.
>
> Also, try to preserve the version tag in your subject for all the
> patches so that we can easily identify the latest version of the
> series, like:
>
> [PATCH v5 3/4] ...
>
> And, typically "RESEND" means there are no code change.
I see, I just make up my mind whether code style is new version
before. I won't again.

Thank you very much.
>
> Regards,
> John
>
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>

-- 
Randy Li
The third produce department

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