linux-kernel - Re: [PATCH 1/2] usb: dwc2: host: Fix missing device insertions

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Date:	Fri, 30 Oct 2015 20:38:41 +0000
From:	John Youn <John.Youn@...opsys.com>
To:	Douglas Anderson <dianders@...omium.org>,
	John Youn <John.Youn@...opsys.com>,
	"balbi@...com" <balbi@...com>
CC:	Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	"linux-rockchip@...ts.infradead.org" 
	<linux-rockchip@...ts.infradead.org>,
	Julius Werner <jwerner@...omium.org>,
	"gregory.herrero@...el.com" <gregory.herrero@...el.com>,
	"yousaf.kaukab@...el.com" <yousaf.kaukab@...el.com>,
	"dinguyen@...nsource.altera.com" <dinguyen@...nsource.altera.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: dwc2: host: Fix missing device insertions

On 10/16/2015 3:10 PM, Douglas Anderson wrote:
> If you've got your interrupt signals bouncing a bit as you insert your
> USB device, you might end up in a state when the device is connected but
> the driver doesn't know it.
> 
> Specifically, the observed order is:
>  1. hardware sees connect
>  2. hardware sees disconnect
>  3. hardware sees connect
>  4. dwc2_port_intr() - clears connect interrupt
>  5. dwc2_handle_common_intr() - calls dwc2_hcd_disconnect()
> 
> Now you'll be stuck with the cable plugged in and no further interrupts
> coming in but the driver will think we're disconnected.
> 
> We'll fix this by checking for the missing connect interrupt and
> re-connecting after the disconnect is posted.  We don't skip the
> disconnect because if there is a transitory disconnect we really want to
> de-enumerate and re-enumerate.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>  drivers/usb/dwc2/core.h     |  2 ++
>  drivers/usb/dwc2/hcd.c      | 33 +++++++++++++++++++++++++++++++++
>  drivers/usb/dwc2/hcd_intr.c |  6 +-----
>  3 files changed, 36 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
> index ebf2504..30748be 100644
> --- a/drivers/usb/dwc2/core.h
> +++ b/drivers/usb/dwc2/core.h
> @@ -1151,11 +1151,13 @@ static inline int dwc2_hsotg_set_test_mode(struct dwc2_hsotg *hsotg,
>  
>  #if IS_ENABLED(CONFIG_USB_DWC2_HOST) || IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
>  extern int dwc2_hcd_get_frame_number(struct dwc2_hsotg *hsotg);
> +extern void dwc2_hcd_connect(struct dwc2_hsotg *hsotg);
>  extern void dwc2_hcd_disconnect(struct dwc2_hsotg *hsotg);
>  extern void dwc2_hcd_start(struct dwc2_hsotg *hsotg);
>  #else
>  static inline int dwc2_hcd_get_frame_number(struct dwc2_hsotg *hsotg)
>  { return 0; }
> +static inline void dwc2_hcd_connect(struct dwc2_hsotg *hsotg) {}
>  static inline void dwc2_hcd_disconnect(struct dwc2_hsotg *hsotg) {}
>  static inline void dwc2_hcd_start(struct dwc2_hsotg *hsotg) {}
>  static inline void dwc2_hcd_remove(struct dwc2_hsotg *hsotg) {}
> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> index af4e4a2..4d2bc50 100644
> --- a/drivers/usb/dwc2/hcd.c
> +++ b/drivers/usb/dwc2/hcd.c
> @@ -268,6 +268,22 @@ static void dwc2_hcd_cleanup_channels(struct dwc2_hsotg *hsotg)
>  }
>  
>  /**
> + * dwc2_hcd_connect() - Handles connect of the HCD
> + *
> + * @hsotg: Pointer to struct dwc2_hsotg
> + *
> + * Must be called with interrupt disabled and spinlock held
> + */
> +void dwc2_hcd_connect(struct dwc2_hsotg *hsotg)
> +{
> +	if (hsotg->lx_state != DWC2_L0)
> +		usb_hcd_resume_root_hub(hsotg->priv);
> +
> +	hsotg->flags.b.port_connect_status_change = 1;
> +	hsotg->flags.b.port_connect_status = 1;
> +}
> +
> +/**
>   * dwc2_hcd_disconnect() - Handles disconnect of the HCD
>   *
>   * @hsotg: Pointer to struct dwc2_hsotg
> @@ -277,6 +293,7 @@ static void dwc2_hcd_cleanup_channels(struct dwc2_hsotg *hsotg)
>  void dwc2_hcd_disconnect(struct dwc2_hsotg *hsotg)
>  {
>  	u32 intr;
> +	u32 hprt0;
>  
>  	/* Set status flags for the hub driver */
>  	hsotg->flags.b.port_connect_status_change = 1;
> @@ -315,6 +332,22 @@ void dwc2_hcd_disconnect(struct dwc2_hsotg *hsotg)
>  		dwc2_hcd_cleanup_channels(hsotg);
>  
>  	dwc2_host_disconnect(hsotg);
> +
> +	/*
> +	 * Add an extra check here to see if we're actually connected but
> +	 * we don't have a detection interrupt pending.  This can happen if:
> +	 *   1. hardware sees connect
> +	 *   2. hardware sees disconnect
> +	 *   3. hardware sees connect
> +	 *   4. dwc2_port_intr() - clears connect interrupt
> +	 *   5. dwc2_handle_common_intr() - calls here
> +	 *
> +	 * Without the extra check here we will end calling disconnect
> +	 * and won't get any future interrupts to handle the connect.
> +	 */
> +	hprt0 = dwc2_readl(hsotg->regs + HPRT0);
> +	if (!(hprt0 & HPRT0_CONNDET) && (hprt0 & HPRT0_CONNSTS))
> +		dwc2_hcd_connect(hsotg);

I'm a little bit wary of this as it will also run when you unload
the module with a device connected. However I can't produce any
negative results from that. Will it work if you handle it just
for the disconnect interrupt?

John


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