linux-kernel - Re: [PATCH 3/4] input: ti_tsc: Enable shared IRQ for TSC and add overrun, underflow checks

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Message-ID: <20130816213132.GD2636@gmail.com>
Date:	Fri, 16 Aug 2013 22:31:33 +0100
From:	"Zubair Lutfullah :" <zubair.lutfullah@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Zubair Lutfullah <zubair.lutfullah@...il.com>, jic23@....ac.uk,
	dmitry.torokhov@...il.com, sameo@...ux.intel.com,
	lee.jones@...aro.org, linux-iio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, Russ.Dill@...com
Subject: Re: [PATCH 3/4] input: ti_tsc: Enable shared IRQ for TSC and add
 overrun, underflow checks

On Fri, Aug 16, 2013 at 11:14:09AM +0200, Sebastian Andrzej Siewior wrote:
> * Zubair Lutfullah | 2013-08-13 17:48:18 [+0100]:
> >+	if ((status & IRQENB_FIFO0OVRRUN) ||
> >+			(status & IRQENB_FIFO0UNDRFLW)) {
> >+
> >+		config = titsc_readl(ts_dev, REG_CTRL);
> >+		config &= ~(CNTRLREG_TSCSSENB);
> >+		titsc_writel(ts_dev, REG_CTRL, config);
> >+
> >+		if (status & IRQENB_FIFO0UNDRFLW) {
> >+			titsc_writel(ts_dev, REG_IRQSTATUS,
> >+				(status | IRQENB_FIFO0UNDRFLW));
> >+			irqclr |= IRQENB_FIFO0UNDRFLW;
> >+		} else {
> >+			titsc_writel(ts_dev, REG_IRQSTATUS,
> >+				(status | IRQENB_FIFO0OVRRUN));
> >+			irqclr |= IRQENB_FIFO0OVRRUN;
> >+		}
> 
> You don't do anything on overflow / underflow. Is this due to the fact
> once enabled for FIFO1 it also triggers for FIFO0?
> 
The TSCADC module doesn't recover from these interrupts.

> >+		titsc_writel(ts_dev, REG_CTRL,
> >+			(config | CNTRLREG_TSCSSENB));

The fix is to re-enable the module after disabling 
and clearing the interrupts.

That is what the handler is doing.
> >+	} else if (status & IRQENB_FIFO0THRES) {
> > 		titsc_read_coordinates(ts_dev, &x, &y, &z1, &z2);
> > 
> > 		if (ts_dev->pen_down && z1 != 0 && z2 != 0) {
> >@@ -317,9 +342,11 @@ static irqreturn_t titsc_irq(int irq, void *dev)
> > 	}
> > 
> > 	if (irqclr) {
> >-		titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
> >+		titsc_writel(ts_dev, REG_IRQSTATUS, (status | irqclr));
> 
> Shouldn't FIFO1UNDRFLW & OVRRUN be handled by the adc driver? Why do you
> or the unhandled bits as well here?
FIFO1 is only used by TSC. ADC doesn't touch it.
> 
> > 		am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
> >-		return IRQ_HANDLED;
> >+		status = titsc_readl(ts_dev, REG_IRQSTATUS);
> >+		if (status == false)
> >+			return IRQ_HANDLED;
> 
> And why this? If you something you handled it, if you didn't you return
> NONE. Why does it depend on REG_IRQSTATUS?

These quirks are to handle the situation where both IRQs happen
simultaneously. Which can occur when someone is using the TSC
while continuously sampling using the ADC.

REG_IRQSTATUS has flags for FIFO0 used by ADC as well.

If there are still those IRQs to handle, then IRQ_NONE is returned.
Otherwise, all IRQ flags are clear so IRQ_HANDLED is returned.

Thanks
Zubair
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