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

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Date:   Tue, 23 Aug 2016 13:46:14 -0700
From:   John Youn <John.Youn@...opsys.com>
To:     Randy Li <ayaka@...lik.info>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
CC:     "John.Youn@...opsys.com" <John.Youn@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "eddie.cai@...k-chips.com" <eddie.cai@...k-chips.com>,
        "randy.li@...k-chips.com" <randy.li@...k-chips.com>,
        "kishon@...com" <kishon@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "heiko@...ech.de" <heiko@...ech.de>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>
Subject: Re: [RESEND PATCH 3/4] usb: dwc2: assert phy reset when waking up in
 rk3288 platform

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.

> +			 */
> +			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.

Also, I'd rather see a generic quirk property that you set for your
platform.

Something like "phy_reset_on_wakeup_quirk".

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.

Regards,
John