[PATCH v2] i2c: designware: amdisp: Fix resume-probe race condition issue

[Pratap Nirujogi <pratap.nirujogi@amd.com>]

Identified resume-probe race condition in kernel v7.0 with the commit
38fa29b01a6a ("i2c: designware: Combine the init functions"),but this
issue existed from the beginning though not detected.

The amdisp i2c device requires ISP to be in power-on state for probe
to succeed. To meet this requirement, this device is added to genpd
to control ISP power using runtime PM. The pm_runtime_get_sync() called
before i2c_dw_probe() triggers PM resume, which powers on ISP and also
invokes the amdisp i2c runtime resume before the probe completes resulting
in this race condition and a NULL dereferencing issue in v7.0

Fix this race condition by using the genpd APIs directly during probe:
  - Call dev_pm_genpd_resume() to Power ON ISP before probe
  - Call dev_pm_genpd_suspend() to Power OFF ISP after probe
  - Set the device to suspended state with pm_runtime_set_suspended()
  - Enable runtime PM only after the device is fully initialized

Fixes: d6263c468a761 ("i2c: amd-isp: Add ISP i2c-designware driver")
Co-developed-by: Bin Du <bin.du@amd.com>
Signed-off-by: Bin Du <bin.du@amd.com>
Signed-off-by: Pratap Nirujogi <pratap.nirujogi@amd.com>
---
Changes v1 -> v2:

* Fixed resume-probe race condition issue
* Removed NULL check in runtime_resume
* Updated Fixes tag with appropriate commit
* Added Signed-off-by for Co-developed-by tag

 drivers/i2c/busses/i2c-designware-amdisp.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-amdisp.c b/drivers/i2c/busses/i2c-designware-amdisp.c
index c48728ad9f6f2..9f0ec0fae6f23 100644
--- a/drivers/i2c/busses/i2c-designware-amdisp.c
+++ b/drivers/i2c/busses/i2c-designware-amdisp.c
@@ -7,6 +7,7 @@
 
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
 #include <linux/soc/amd/isp4_misc.h>
 
@@ -76,22 +77,20 @@ static int amd_isp_dw_i2c_plat_probe(struct platform_device *pdev)
 
 	device_enable_async_suspend(&pdev->dev);
 
-	pm_runtime_enable(&pdev->dev);
-	pm_runtime_get_sync(&pdev->dev);
-
+	dev_pm_genpd_resume(&pdev->dev);
 	ret = i2c_dw_probe(isp_i2c_dev);
 	if (ret) {
 		dev_err_probe(&pdev->dev, ret, "i2c_dw_probe failed\n");
 		goto error_release_rpm;
 	}
-
-	pm_runtime_put_sync(&pdev->dev);
+	dev_pm_genpd_suspend(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
 
 	return 0;
 
 error_release_rpm:
 	amd_isp_dw_i2c_plat_pm_cleanup(isp_i2c_dev);
-	pm_runtime_put_sync(&pdev->dev);
 	return ret;
 }
 
-- 
2.43.0