Input: zforce_ts - ensure that pm_stay_awake() and pm_relax() are balanced

There is a small chance that ts->suspending flag may change while the
interrupt handler is running. To make sure call to pm_relax() is not
skipped on accident use a temporary to hold the original value at the
beginning of interrupt. Use READ_ONCE() so that the value is actually
fetched at the right time.

Tested-by: Andreas Kemnade <andreas@kemnade.info> # Tolino Shine2HD
Link: https://lore.kernel.org/r/20240824055047.1706392-8-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/touchscreen/zforce_ts.c b/drivers/input/touchscreen/zforce_ts.c
index afeafa5899282e99e980035f336e9e9dfef031a2..004ef728fb90af97a117dbb6977dde8e075ae7d6 100644 (file)
--- a/drivers/input/touchscreen/zforce_ts.c
+++ b/drivers/input/touchscreen/zforce_ts.c
@@ -454,6 +454,7 @@ static irqreturn_t zforce_irq_thread(int irq, void *dev_id)
        int ret;
        u8 payload_buffer[FRAME_MAXSIZE];
        u8 *payload;
+       bool suspending;
 
        /*
         * When still suspended, return.
@@ -467,7 +468,8 @@ static irqreturn_t zforce_irq_thread(int irq, void *dev_id)
        dev_dbg(&client->dev, "handling interrupt\n");
 
        /* Don't emit wakeup events from commands run by zforce_suspend */
-       if (!ts->suspending && device_may_wakeup(&client->dev))
+       suspending = READ_ONCE(ts->suspending);
+       if (!suspending && device_may_wakeup(&client->dev))
                pm_stay_awake(&client->dev);
 
        /*
@@ -495,7 +497,7 @@ static irqreturn_t zforce_irq_thread(int irq, void *dev_id)
                         * Always report touch-events received while
                         * suspending, when being a wakeup source
                         */
-                       if (ts->suspending && device_may_wakeup(&client->dev))
+                       if (suspending && device_may_wakeup(&client->dev))
                                pm_wakeup_event(&client->dev, 500);
                        zforce_touch_event(ts, &payload[RESPONSE_DATA]);
                        break;
@@ -548,7 +550,7 @@ static irqreturn_t zforce_irq_thread(int irq, void *dev_id)
                }
        } while (gpiod_get_value_cansleep(ts->gpio_int));
 
-       if (!ts->suspending && device_may_wakeup(&client->dev))
+       if (!suspending && device_may_wakeup(&client->dev))
                pm_relax(&client->dev);
 
        dev_dbg(&client->dev, "finished interrupt\n");
@@ -584,7 +586,9 @@ static int zforce_suspend(struct device *dev)
        int ret = 0;
 
        mutex_lock(&input->mutex);
-       ts->suspending = true;
+
+       WRITE_ONCE(ts->suspending, true);
+       smp_mb();
 
        /*
         * When configured as a wakeup source device should always wake
@@ -615,7 +619,9 @@ static int zforce_suspend(struct device *dev)
        ts->suspended = true;
 
 unlock:
-       ts->suspending = false;
+       smp_mb();
+       WRITE_ONCE(ts->suspending, false);
+
        mutex_unlock(&input->mutex);
 
        return ret;