[PATCH v2 1/1] iio: imx8qxp-adc: fix irq flood when call imx8qxp_adc_read_raw()

From: Frank Li
Date: Thu Dec 01 2022 - 09:02:13 EST


irq flood happen when run
cat /sys/bus/iio/devices/iio:device0/in_voltage1_raw

imx8qxp_adc_read_raw()
{
...
enable irq
/* adc start */
writel(1, adc->regs + IMX8QXP_ADR_ADC_SWTRIG);
^^^^ trigger irq flood.
wait_for_completion_interruptible_timeout();
readl(adc->regs + IMX8QXP_ADR_ADC_RESFIFO);
^^^^ clear irq here.
...
}

There is only FIFO watermark interrupt at this ADC controller.
IRQ line will be assert until software read data from FIFO.
So IRQ flood happen during wait_for_completion_interruptible_timeout().

Move FIFO read into irq handle to avoid irq flood.

Fixes: 1e23dcaa1a9f ("iio: imx8qxp-adc: Add driver support for NXP IMX8QXP ADC")
Cc: stable@xxxxxxxxxxxxxxx

Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
---
Change from v1 to v2
- move complete() after read fifo


drivers/iio/adc/imx8qxp-adc.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/imx8qxp-adc.c b/drivers/iio/adc/imx8qxp-adc.c
index 36777b827165..f5a0fc9e64c5 100644
--- a/drivers/iio/adc/imx8qxp-adc.c
+++ b/drivers/iio/adc/imx8qxp-adc.c
@@ -86,6 +86,8 @@

#define IMX8QXP_ADC_TIMEOUT msecs_to_jiffies(100)

+#define IMX8QXP_ADC_MAX_FIFO_SIZE 16
+
struct imx8qxp_adc {
struct device *dev;
void __iomem *regs;
@@ -95,6 +97,7 @@ struct imx8qxp_adc {
/* Serialise ADC channel reads */
struct mutex lock;
struct completion completion;
+ u32 fifo[IMX8QXP_ADC_MAX_FIFO_SIZE];
};

#define IMX8QXP_ADC_CHAN(_idx) { \
@@ -238,8 +241,7 @@ static int imx8qxp_adc_read_raw(struct iio_dev *indio_dev,
return ret;
}

- *val = FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
- readl(adc->regs + IMX8QXP_ADR_ADC_RESFIFO));
+ *val = adc->fifo[0];

mutex_unlock(&adc->lock);
return IIO_VAL_INT;
@@ -265,10 +267,15 @@ static irqreturn_t imx8qxp_adc_isr(int irq, void *dev_id)
{
struct imx8qxp_adc *adc = dev_id;
u32 fifo_count;
+ int i;

fifo_count = FIELD_GET(IMX8QXP_ADC_FCTRL_FCOUNT_MASK,
readl(adc->regs + IMX8QXP_ADR_ADC_FCTRL));

+ for (i = 0; i < fifo_count; i++)
+ adc->fifo[i] = FIELD_GET(IMX8QXP_ADC_RESFIFO_VAL_MASK,
+ readl_relaxed(adc->regs + IMX8QXP_ADR_ADC_RESFIFO));
+
if (fifo_count)
complete(&adc->completion);

--
2.34.1