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

["Mario Limonciello (AMD) (kernel.org)" <superm1@kernel.org>]

On 3/20/2026 3:12 PM, Pratap Nirujogi wrote:
> 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>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> ---
> 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;
>   }
>