linux-kernel - Re: [PATCH 4/4] iio: ti_am335x_adc: Add continuous sampling and trigger support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130816211809.GA2636@gmail.com>
Date:	Fri, 16 Aug 2013 22:18:10 +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, linux-iio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, Russ.Dill@...com
Subject: Re: [PATCH 4/4] iio: ti_am335x_adc: Add continuous sampling and
 trigger support

On Fri, Aug 16, 2013 at 02:53:40PM +0200, Sebastian Andrzej Siewior wrote:
> * Zubair Lutfullah | 2013-08-13 21:05:03 [+0100]:
> 
> >diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> >index 3ceac3e..0d7e313 100644
> >--- a/drivers/iio/adc/ti_am335x_adc.c
> >+++ b/drivers/iio/adc/ti_am335x_adc.c
> >@@ -24,16 +24,28 @@
> …
> >+static irqreturn_t tiadc_irq(int irq, void *private)
> >+{
> >+	struct iio_dev *idev = private;
> >+	struct tiadc_device *adc_dev = iio_priv(idev);
> >+	unsigned int status, config;
> >+	status = tiadc_readl(adc_dev, REG_IRQSTATUS);
> >+
> >+	/* FIFO Overrun. Clear flag. Disable/Enable ADC to recover */
> >+	if (status & IRQENB_FIFO1OVRRUN) {
> >+		config = tiadc_readl(adc_dev, REG_CTRL);
> >+		config &= ~(CNTRLREG_TSCSSENB);
> >+		tiadc_writel(adc_dev, REG_CTRL, config);
> >+		tiadc_writel(adc_dev, REG_IRQSTATUS, IRQENB_FIFO1OVRRUN |
> >+				IRQENB_FIFO1UNDRFLW | IRQENB_FIFO1THRES);
> >+		tiadc_writel(adc_dev, REG_CTRL, (config | CNTRLREG_TSCSSENB));
> 
> I have no idea how other handle this but shouldn't you somehow inform
> *anyone* that you lost some samples due to this overrun?
> 
> Sebastian

The ref manual states that TSCADC module doesn't recover 
from overrun interrupts. Thats why the disable enable of
the module here to handle the situation.
And of course, clearing interrupt flags.
The data is lost.

Informing someone about lost samples is important indeed.
But a print statement in this area causes more overruns.

I'm open to some input on how to inform userspace of such 
a situation.

Thanks
Zubair
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/