[PATCH v3] i2c: imx-lpi2c: mark I2C adapter when hardware is powered down

[Carlos Song (OSS)]

From: Carlos Song <carlos.song at nxp.com>

On some i.MX platforms, certain I2C client drivers keep a periodic
workqueue which continues to trigger I2C transfers.

During system suspend/resume, there exists a time window between:
  - suspend_noirq and the system entering suspend
  - the system starting to resume and resume_noirq

In this window, the I2C controller resources such as clock and pinctrl
may already be disabled or not yet restored.

If a workqueue triggers an I2C transfer in this period, the driver
attempts to access I2C registers while the hardware resources are
unavailable, which may lead to system hang.

Mark the I2C adapter as suspended during noirq suspend and block new
transfers until resume, ensuring that I2C transfers are only issued
when hardware resources are available.

Fixes: 1ee867e465c1 ("i2c: imx-lpi2c: add target mode support")
Cc: stable at vger.kernel.org
Signed-off-by: Carlos Song <carlos.song at nxp.com>
---
Change for v3:
  - Remake commit log including the issue detail.
Change for v2:
  - Call i2c_mark_adapter_suspended() before pm_runtime_force_suspend()
    to prevent potential deadlock if a transfer is active during suspend.
  - Roll back with i2c_mark_adapter_resumed() if pm_runtime_force_suspend()
    fails.
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 7adbeae9cb35..4929f85ab485 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -1668,7 +1668,18 @@ static int __maybe_unused lpi2c_runtime_resume(struct device *dev)
 
 static int __maybe_unused lpi2c_suspend_noirq(struct device *dev)
 {
-	return pm_runtime_force_suspend(dev);
+	struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
+	int ret;
+
+	i2c_mark_adapter_suspended(&lpi2c_imx->adapter);
+
+	ret = pm_runtime_force_suspend(dev);
+	if (ret) {
+		i2c_mark_adapter_resumed(&lpi2c_imx->adapter);
+		return ret;
+	}
+
+	return 0;
 }
 
 static int __maybe_unused lpi2c_resume_noirq(struct device *dev)
@@ -1688,6 +1699,8 @@ static int __maybe_unused lpi2c_resume_noirq(struct device *dev)
 	if (lpi2c_imx->target)
 		lpi2c_imx_target_init(lpi2c_imx);
 
+	i2c_mark_adapter_resumed(&lpi2c_imx->adapter);
+
 	return 0;
 }
 
-- 
2.43.0