[PATCH 1/6] iio: adc: versal-sysmon: fix race in interrupt teardown

[Amit Kumar Mahapatra]

sysmon_disable_interrupts() masks all interrupts, clears masked_temp and
cancels the unmask worker, but leaves the interrupt handler live. A
worker that is already running can re-enable an alarm through IER after
the mask write. If that alarm fires, the handler queues the worker again
after cancel_delayed_work_sync() has returned. On unbind this action runs
before devm releases the IRQ, so the queued work can run after the
devm-allocated iio_dev that embeds it has been freed.

Disable the IRQ first so that no handler is running or can start, then
clear masked_temp and cancel the worker, and mask all interrupts last,
once nothing is left that can unmask them. Record the IRQ number for
this.

Fixes: c7f7eb10638f ("iio: adc: versal-sysmon: add threshold event support")
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra at amd.com>
---
 drivers/iio/adc/versal-sysmon-core.c | 5 ++++-
 drivers/iio/adc/versal-sysmon.h      | 2 ++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/versal-sysmon-core.c b/drivers/iio/adc/versal-sysmon-core.c
index 1b55d343982e..6b9a58e19831 100644
--- a/drivers/iio/adc/versal-sysmon-core.c
+++ b/drivers/iio/adc/versal-sysmon-core.c
@@ -781,12 +781,14 @@ static void sysmon_disable_interrupts(void *data)
 {
 	struct sysmon *sysmon = data;
 
-	regmap_write(sysmon->regmap, SYSMON_IDR, SYSMON_INTR_ALL_MASK);
+	disable_irq(sysmon->irq);
 
 	scoped_guard(spinlock_irq, &sysmon->irq_lock)
 		sysmon->masked_temp = 0;
 
 	cancel_delayed_work_sync(&sysmon->sysmon_unmask_work);
+
+	regmap_write(sysmon->regmap, SYSMON_IDR, SYSMON_INTR_ALL_MASK);
 }
 
 static int sysmon_init_interrupt(struct sysmon *sysmon,
@@ -807,6 +809,7 @@ static int sysmon_init_interrupt(struct sysmon *sysmon,
 	if (ret)
 		return ret;
 	sysmon->temp_mask = imr & SYSMON_TEMP_INTR_MASK;
+	sysmon->irq = irq;
 
 	ret = devm_request_irq(dev, irq, sysmon_iio_irq, 0, "sysmon-irq", indio_dev);
 	if (ret)
diff --git a/drivers/iio/adc/versal-sysmon.h b/drivers/iio/adc/versal-sysmon.h
index bb9a75bf71c0..701ef9b56263 100644
--- a/drivers/iio/adc/versal-sysmon.h
+++ b/drivers/iio/adc/versal-sysmon.h
@@ -85,6 +85,7 @@ struct regmap;
  * @regmap: register map for hardware access
  * @lock: protects read-modify-write sequences on threshold registers
  *        and cached state that spans multiple regmap calls
+ * @irq: interrupt number, 0 when events are not supported
  * @irq_lock: protects interrupt mask register updates (MMIO path only)
  * @masked_temp: currently masked temperature alarm bits
  * @temp_mask: temperature interrupt configuration mask
@@ -101,6 +102,7 @@ struct sysmon {
 	 * that spans multiple regmap calls.
 	 */
 	struct mutex lock;
+	int irq;
 	/*
 	 * Protects interrupt mask register updates.  Only used on the
 	 * MMIO path (fast_io regmap); I2C has no IRQ and never reaches
-- 
2.34.1