iio: adc: at91: unbreak channel adc channel 3

The driver always assumes that an input device has been created when
reading channel 3. This causes a kernel panic when dereferencing
st->ts_input.

The change was introduced in
commit 84882b060301 ("iio: adc: at91_adc: Add support for touchscreens
without TSMR"). Earlier versions only entered that part of the if-else
statement if only the following flags are set:

AT91_ADC_IER_XRDY | AT91_ADC_IER_YRDY | AT91_ADC_IER_PRDY

Signed-off-by: Anders Darander <anders@chargestorm.se>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 52430ba171f3..0438c68015e8 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -381,8 +381,8 @@ static irqreturn_t at91_adc_rl_interrupt(int irq, void *private)
                 st->ts_bufferedmeasure = false;
                 input_report_key(st->ts_input, BTN_TOUCH, 0);
                 input_sync(st->ts_input);
-        } else if (status & AT91_ADC_EOC(3)) {
-                /* Conversion finished */
+        } else if (status & AT91_ADC_EOC(3) && st->ts_input) {
+                /* Conversion finished and we've a touchscreen */
                 if (st->ts_bufferedmeasure) {
                         /*
                          * Last measurement is always discarded, since it can