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Commit 75c1d2a1 authored by Azhar Shaikh's avatar Azhar Shaikh Committed by Gerrit - the friendly Code Review server
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usb: dwc3: Offload IRQ handling to softirq context 



Move interrupt handling from threaded IRQ context to a tasklet.
This may help in reducing latencies associated with starvation
caused by high priority softirq over threaded USB IRQ.

Change-Id: I2f988be9c484a6ee59236d9dfd7f06f07414ee96
Signed-off-by: default avatarAzhar Shaikh <azhars@codeaurora.org>
parent 0191ccd5

drivers/usb/dwc3/core.h

+2 −0
Original line number Diff line number Diff line
@@ -819,6 +819,7 @@ struct dwc3_scratchpad_array { 
 * @in_lpm: if 1, indicates that the controller is in low power mode (no clocks)

 * @tx_fifo_size: Available RAM size for TX fifo allocation

 * @irq: irq number

 * @bh: tasklet which handles the interrupt

 * @irq_cnt: total irq count

 * @bh_completion_time: time taken for taklet completion

 * @bh_handled_evt_cnt: no. of events handled by tasklet per interrupt
@@ -964,6 +965,7 @@ struct dwc3 { 


	/* IRQ timing statistics */

	int			irq;

	struct tasklet_struct	bh;

	unsigned long		irq_cnt;

	unsigned                bh_completion_time[MAX_INTR_STATS];

	unsigned                bh_handled_evt_cnt[MAX_INTR_STATS];

drivers/usb/dwc3/gadget.c

+23 −6
Original line number Diff line number Diff line
@@ -2161,8 +2161,8 @@ static int dwc3_gadget_start(struct usb_gadget *g, 
	int			irq;



	irq = platform_get_irq(to_platform_device(dwc->dev), 0);

	ret = request_threaded_irq(irq, dwc3_interrupt, dwc3_thread_interrupt,

			IRQF_SHARED, "dwc3", dwc);

	dwc->irq = irq;

	ret = request_irq(irq, dwc3_interrupt, IRQF_SHARED, "dwc3", dwc);

	if (ret) {

		dev_err(dwc->dev, "failed to request irq #%d --> %d\n",

				irq, ret);
@@ -2207,9 +2207,12 @@ static int dwc3_gadget_stop(struct usb_gadget *g, 
	unsigned long		flags;

	int			irq;



	dwc3_gadget_disable_irq(dwc);



	tasklet_kill(&dwc->bh);



	spin_lock_irqsave(&dwc->lock, flags);



	dwc3_gadget_disable_irq(dwc);

	__dwc3_gadget_ep_disable(dwc->eps[0]);

	__dwc3_gadget_ep_disable(dwc->eps[1]);
@@ -3448,6 +3451,15 @@ static irqreturn_t dwc3_process_event_buf(struct dwc3 *dwc, u32 buf) 
	return ret;

}



static void dwc3_interrupt_bh(unsigned long param)

{

	struct dwc3 *dwc = (struct dwc3 *) param;



	pm_runtime_get(dwc->dev);

	dwc3_thread_interrupt(dwc->irq, dwc);

	enable_irq(dwc->irq);

}



static irqreturn_t dwc3_thread_interrupt(int irq, void *_dwc)

{

	struct dwc3 *dwc = _dwc;
@@ -3541,10 +3553,12 @@ static irqreturn_t dwc3_interrupt(int irq, void *_dwc) 
	dwc->irq_event_count[dwc->irq_dbg_index] = temp_cnt / 4;

	dwc->irq_dbg_index = (dwc->irq_dbg_index + 1) % MAX_INTR_STATS;



	if (ret == IRQ_WAKE_THREAD)

		pm_runtime_get(dwc->dev);

	if (ret == IRQ_WAKE_THREAD) {

		disable_irq_nosync(irq);

		tasklet_schedule(&dwc->bh);

	}



	return ret;

	return IRQ_HANDLED;

}



/**
@@ -3590,6 +3604,9 @@ int dwc3_gadget_init(struct dwc3 *dwc) 
		goto err3;

	}



	dwc->bh.func = dwc3_interrupt_bh;

	dwc->bh.data = (unsigned long)dwc;



	dwc->gadget.ops			= &dwc3_gadget_ops;

	dwc->gadget.max_speed		= USB_SPEED_SUPER;

	dwc->gadget.speed		= USB_SPEED_UNKNOWN;