RE: BBB IIO ADC access not working

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> -----Original Message-----
> From: Michael Welling [mailto:mwelling79@xxxxxxxxx] On Behalf 
> Of Michael Welling
> Sent: Wednesday, August 19, 2015 10:53 AM
> To: Greg Wilson-Lindberg
> Cc: Daniel Baluta; linux-iio@xxxxxxxxxxxxxxx
> Subject: Re: BBB IIO ADC access not working
> 
> On Wed, Aug 19, 2015 at 09:27:02AM -0700, Greg Wilson-Lindberg wrote:
> >  
> > 
> > > -----Original Message-----
> > > From: Michael Welling [mailto:mwelling79@xxxxxxxxx] On Behalf Of 
> > > Michael Welling
> > > Sent: Tuesday, August 18, 2015 3:31 PM
> > > To: Greg Wilson-Lindberg
> > > Cc: Daniel Baluta; linux-iio@xxxxxxxxxxxxxxx
> > > Subject: Re: BBB IIO ADC access not working
> > > 
> > > On Tue, Aug 18, 2015 at 03:11:13PM -0700, Greg 
> Wilson-Lindberg wrote:
> > > >  
> > > > 
> > > > > I found that handling the IRQENB_EOS interrupt in the ADC
> > > is causing
> > > > > an undesired effect. After enabling the ADC buffer mode and 
> > > > > disabling it the coordinate readings work but the touch
> > > release is
> > > > > no longer detected.
> > > > 
> > > > Can we put your code in the touch screen handler? The tsc
> > > code is writing to the IRQSTATUS register, not the IRQCLR 
> register.
> > > > 
> > > 
> > > Actually using the IRQCLR disables the IRQ instead of clearing it 
> > > and that was not my intent. This is why the pen releases 
> where not 
> > > working, the tsc driver relies on the EOS interrupt to write the 
> > > step register because it is using a one shot hardware mode.
> > > 
> > > Since the IRQENB_EOS is not used by the ADC driver it can be 
> > > disabled when in buffered mode which is triggering faster 
> than the 
> > > isr can handle it.
> > > 
> > > See patch below.
> > > 
> > > Though it allows for the repeated enabling and disabling of the 
> > > buffer the touchscreen gets a bunch of unexpected 
> releases and the 
> > > readings are very jittery.
> > > 
> > > diff --git a/drivers/iio/adc/ti_am335x_adc.c 
> > > b/drivers/iio/adc/ti_am335x_adc.c index a0e7161..9945e4a 100644
> > > --- a/drivers/iio/adc/ti_am335x_adc.c
> > > +++ b/drivers/iio/adc/ti_am335x_adc.c
> > > @@ -177,6 +177,7 @@ static int 
> tiadc_buffer_preenable(struct iio_dev 
> > > *indio_dev)
> > >  				IRQENB_FIFO1OVRRUN |
> > >  				IRQENB_FIFO1UNDRFLW));
> > >  
> > > +	tiadc_writel(adc_dev, REG_IRQCLR, IRQENB_EOS);
> > >  	/* Flush FIFO. Needed in corner cases in simultaneous 
> tsc/adc use 
> > > */
> > >  	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
> > >  	for (i = 0; i < fifo1count; i++)
> > > @@ -213,6 +214,7 @@ static int tiadc_buffer_predisable(struct 
> > > iio_dev *indio_dev)
> > >  
> > >  	tiadc_writel(adc_dev, REG_IRQCLR, (IRQENB_FIFO1THRES |
> > >  				IRQENB_FIFO1OVRRUN |
> > > IRQENB_FIFO1UNDRFLW));
> > > +	tiadc_writel(adc_dev, REG_IRQENABLE, IRQENB_EOS);
> > >  	am335x_tsc_se_clr(adc_dev->mfd_tscadc,
> > > adc_dev->buffer_en_ch_steps);
> > >  	adc_dev->buffer_en_ch_steps = 0;
> > >  
> > > 
> > 
> > I'm not sure that it's better, but it is different.  The 
> touch screen still locks up, but mouse clicks work.
> 
> This is very disappointing.
> 
> Have you tried reading the ADCs using one shot mode recently?
> 
> IE cat /sys/bus/iio/devices/iio:device0/in_voltageX_raw

I tried that after the system had locked up and what I get back is the Device
or resource is busy.  I restarted the BBB and tried before starting my application
and it worked just fine. I started up the app and the touch screen was 
locked up immediately, mouse clicks delayed about 1/2 second. And I get Device or resource busy from the cat.

> 
> > 
> > > 
> > > 
> > > 
> --
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