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

From: Kishon Vijay Abraham I <kishon@ti.com>
To: Randy Li <ayaka@soulik.info>, <linux-usb@vger.kernel.org>
Cc: <felipe.balbi@linux.intel.com>, <John.Youn@synopsys.com>,
	<mark.rutland@arm.com>, <devicetree@vger.kernel.org>,
	<heiko@sntech.de>, <gregkh@linuxfoundation.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-rockchip@lists.infradead.org>, <robh+dt@kernel.org>,
	<randy.li@rock-chips.com>
Subject: Re: [PATCH v7 3/4] usb: dwc2: assert phy reset when waking up in rk3288 platform
Date: Tue, 6 Sep 2016 10:44:10 +0530	[thread overview]
Message-ID: <57CE50A2.7080502@ti.com> (raw)
In-Reply-To: <1472939729-15187-4-git-send-email-ayaka@soulik.info>

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@soulik.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.

Thanks
Kishon