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Date:   Wed, 12 Jul 2023 16:46:32 +0300
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Subject: Re: [PATCH v3 3/3] usb: dwc3: Modify runtime pm ops to handle bus
 suspend
Content-Language: en-US
To:     Elson Roy Serrao <quic_eserrao@quicinc.com>,
        Thinh.Nguyen@synopsys.com, stern@rowland.harvard.edu
Cc:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, quic_wcheng@quicinc.com,
        quic_jackp@quicinc.com
References: <20230711174320.24058-1-quic_eserrao@quicinc.com>
 <20230711174320.24058-4-quic_eserrao@quicinc.com>
From:   Roger Quadros <rogerq@kernel.org>
In-Reply-To: <20230711174320.24058-4-quic_eserrao@quicinc.com>
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On 11/07/2023 20:43, Elson Roy Serrao wrote:
> The current implementation blocks the runtime pm operations when cable
> is connected. This would block platforms from entering system wide suspend
> during bus suspend scenario. Modify the runtime pm ops to handle bus
> suspend case for such platforms where the controller low power mode
> entry/exit is handled by the glue driver. This enablement is controlled
> through a dt property and platforms capable of detecting bus resume can
> benefit from this feature. Also modify the remote wakeup operations to
> trigger runtime resume before sending wakeup signal.
> 
> Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
> ---
>  drivers/usb/dwc3/core.c   | 26 ++++++++++++++++++++++---
>  drivers/usb/dwc3/core.h   |  3 +++
>  drivers/usb/dwc3/gadget.c | 40 ++++++++++++++++++++++++++++++++-------
>  3 files changed, 59 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index f6689b731718..898c0f68e190 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1534,6 +1534,9 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  	dwc->dis_split_quirk = device_property_read_bool(dev,
>  				"snps,dis-split-quirk");
>  
> +	dwc->allow_rtsusp_on_u3 = device_property_read_bool(dev,
> +				"snps,allow-rtsusp-on-u3");
> +
>  	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
>  	dwc->tx_de_emphasis = tx_de_emphasis;
>  
> @@ -1984,11 +1987,21 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  {
>  	unsigned long	flags;
>  	u32 reg;
> +	int link_state;
>  
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
>  		if (pm_runtime_suspended(dwc->dev))
>  			break;
> +
> +		if (dwc->connected) {
> +			link_state = dwc3_gadget_get_link_state(dwc);
> +			/* bus suspend case */
> +			if (dwc->allow_rtsusp_on_u3 &&
> +			    link_state == DWC3_LINK_STATE_U3> +				break;

dwc3_suspend_common() is called both during runtime suspend and system sleep with
appropriate pm_msg_t argument.
Do you want the same behavior for both cases?

You are not checking if the gadget driver was put into suspend state or not.
So, instead of just checking line state, should we also check that we processed
the suspend interrupt and gadget driver has been suspended as well?
i.e. add a SW flag dwc3->suspended and set it at end of dwc3_suspend_gadget()
and clear it at beginning of dwc3_resume_gadget().
Check for that flag in the above if condition.
i.e. if (dwc->connected && dwc->suspended)

> +			return -EBUSY;
> +		}
>  		dwc3_gadget_suspend(dwc);
>  		synchronize_irq(dwc->irq_gadget);
>  		dwc3_core_exit(dwc);
> @@ -2045,6 +2058,9 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
>  
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
> +		/* bus resume case */
> +		if (dwc->connected)

dwc->connected might get cleard to false if device was disconnected. So this is not reliable.
You might want to set another SW flag to track this special case of suspend
with controller kept active.

> +			break;
>  		ret = dwc3_core_init_for_resume(dwc);
>  		if (ret)
>  			return ret;
> @@ -2123,9 +2139,6 @@ static int dwc3_runtime_suspend(struct device *dev)
>  	struct dwc3     *dwc = dev_get_drvdata(dev);
>  	int		ret;
>  
> -	if (dwc3_runtime_checks(dwc))
> -		return -EBUSY;
> -
Instead of removing this how about modifying dwc3_runtime_checks(). see below.

>  	ret = dwc3_suspend_common(dwc, PMSG_AUTO_SUSPEND);
>  	if (ret)
>  		return ret;
> @@ -2160,9 +2173,15 @@ static int dwc3_runtime_resume(struct device *dev)
>  static int dwc3_runtime_idle(struct device *dev)
>  {
>  	struct dwc3     *dwc = dev_get_drvdata(dev);
> +	int		link_state;
>  
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
> +		link_state = dwc3_gadget_get_link_state(dwc);
> +		/* for bus suspend case return success */
> +		if (dwc->allow_rtsusp_on_u3 && dwc->connected &&
> +		    link_state == DWC3_LINK_STATE_U3)
> +			goto autosuspend;

why not just break?

>  		if (dwc3_runtime_checks(dwc))

what about this dwc3_runtime_checks()?
Looks like the if condition you added above can go in dwc3_runtime_checks() instead.

>  			return -EBUSY;
>  		break;
> @@ -2172,6 +2191,7 @@ static int dwc3_runtime_idle(struct device *dev)
>  		break;
>  	}
>  
> +autosuspend:
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_autosuspend(dev);
>  
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 8b1295e4dcdd..33b2ccbbd963 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1127,6 +1127,8 @@ struct dwc3_scratchpad_array {
>   * @num_ep_resized: carries the current number endpoints which have had its tx
>   *		    fifo resized.
>   * @debug_root: root debugfs directory for this device to put its files in.
> + * @allow_rtsusp_on_u3: true if dwc3 runtime suspend is allowed during bus
> + *			suspend scenario.

what about system sleep?

>   */
>  struct dwc3 {
>  	struct work_struct	drd_work;
> @@ -1343,6 +1345,7 @@ struct dwc3 {
>  	int			last_fifo_depth;
>  	int			num_ep_resized;
>  	struct dentry		*debug_root;
> +	bool			allow_rtsusp_on_u3;
>  };
>  
>  #define INCRX_BURST_MODE 0
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 5fd067151fbf..0797cffa2d48 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2401,15 +2401,21 @@ static int dwc3_gadget_wakeup(struct usb_gadget *g)
>  		return -EINVAL;
>  	}
>  
> -	spin_lock_irqsave(&dwc->lock, flags);
>  	if (!dwc->gadget->wakeup_armed) {
>  		dev_err(dwc->dev, "not armed for remote wakeup\n");
> -		spin_unlock_irqrestore(&dwc->lock, flags);
>  		return -EINVAL;
>  	}
> -	ret = __dwc3_gadget_wakeup(dwc, true);
>  
> +	ret = pm_runtime_resume_and_get(dwc->dev);
> +	if (ret < 0) {
> +		pm_runtime_set_suspended(dwc->dev);
> +		return ret;
> +	}
> +
> +	spin_lock_irqsave(&dwc->lock, flags);
> +	ret = __dwc3_gadget_wakeup(dwc, true);
>  	spin_unlock_irqrestore(&dwc->lock, flags);
> +	pm_runtime_put_noidle(dwc->dev);
>  
>  	return ret;
>  }
> @@ -2428,6 +2434,12 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>  		return -EINVAL;
>  	}
>  
> +	ret = pm_runtime_resume_and_get(dwc->dev);
> +	if (ret < 0) {
> +		pm_runtime_set_suspended(dwc->dev);
> +		return ret;
> +	}
> +
>  	spin_lock_irqsave(&dwc->lock, flags);
>  	/*
>  	 * If the link is in U3, signal for remote wakeup and wait for the
> @@ -2438,6 +2450,7 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>  		ret = __dwc3_gadget_wakeup(dwc, false);
>  		if (ret) {
>  			spin_unlock_irqrestore(&dwc->lock, flags);
> +			pm_runtime_put_noidle(dwc->dev);
>  			return -EINVAL;
>  		}
>  		dwc3_resume_gadget(dwc);
> @@ -2452,6 +2465,7 @@ static int dwc3_gadget_func_wakeup(struct usb_gadget *g, int intf_id)
>  		dev_err(dwc->dev, "function remote wakeup failed, ret:%d\n", ret);
>  
>  	spin_unlock_irqrestore(&dwc->lock, flags);
> +	pm_runtime_put_noidle(dwc->dev);
>  
>  	return ret;
>  }
> @@ -2732,21 +2746,23 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>  	/*
>  	 * Avoid issuing a runtime resume if the device is already in the
>  	 * suspended state during gadget disconnect.  DWC3 gadget was already
> -	 * halted/stopped during runtime suspend.
> +	 * halted/stopped during runtime suspend except for bus suspend case
> +	 * where we would have skipped the controller halt.
>  	 */
>  	if (!is_on) {
>  		pm_runtime_barrier(dwc->dev);
> -		if (pm_runtime_suspended(dwc->dev))
> +		if (pm_runtime_suspended(dwc->dev) && !dwc->connected)

dwc->connected will to to false on disconnect. I'm not sure if we can rely
on this flag here.

>  			return 0;
>  	}
>  
>  	/*
>  	 * Check the return value for successful resume, or error.  For a
>  	 * successful resume, the DWC3 runtime PM resume routine will handle
> -	 * the run stop sequence, so avoid duplicate operations here.
> +	 * the run stop sequence except for bus resume case, so avoid
> +	 * duplicate operations here.
>  	 */
>  	ret = pm_runtime_get_sync(dwc->dev);
> -	if (!ret || ret < 0) {
> +	if ((!ret && !dwc->connected) || ret < 0) {

Why this check?

>  		pm_runtime_put(dwc->dev);
>  		if (ret < 0)
>  			pm_runtime_set_suspended(dwc->dev);
> @@ -4331,6 +4347,8 @@ static void dwc3_gadget_suspend_interrupt(struct dwc3 *dwc,
>  	}
>  
>  	dwc->link_state = next;
> +	pm_runtime_mark_last_busy(dwc->dev);
> +	pm_request_autosuspend(dwc->dev);

Not here. You should do this in dwc3_suspend_gadget() after gadget driver
has completed suspend.

>  }
>  
>  static void dwc3_gadget_interrupt(struct dwc3 *dwc,
> @@ -4718,7 +4736,15 @@ void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
>  {
>  	if (dwc->pending_events) {
>  		dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
> +		pm_runtime_put(dwc->dev);

Why the put here?

>  		dwc->pending_events = false;
>  		enable_irq(dwc->irq_gadget);
> +		/*
> +		 * We have only stored the pending events as part
> +		 * of dwc3_interrupt() above, but those events are
> +		 * not yet handled. So explicitly invoke the
> +		 * interrupt handler for handling those events.
> +		 */
> +		dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
>  	}
>  }

-- 
cheers,
-roger