Re: [PATCH v1] i2c: designware: amdisp: Fix null pointer dereference in runtime resume

[Nirujogi, Pratap]

Hi Andy,

On 3/10/2026 7:21 AM, Andy Shevchenko wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> On Mon, Mar 09, 2026 at 06:00:01PM -0400, Pratap Nirujogi wrote:
> > Add NULL check for i_dev->map before calling i2c_dw_init() in the
> > runtime resume path. The regmap may not be initialized yet when
> > runtime PM tries to resume the device early in the probe sequence,
> > leading to a NULL pointer dereference. Skip the i2c_dw_init() call
> > if regmap is not yet created.
> >
> > This race condition occurs when runtime PM resume is triggered before
> > i2c_dw_probe() completes the regmap initialization and was observed in
> > kernel v7.0 where the order of device enumeration has changed because
> > of the changes in registering the device sources in the device hierarchy.
>
> > Co-developed-by: Bin Du <Bin.Du@xxxxxxx>
>
> Please, read Submitting Patches on the tags, especially how to correctly use
> Co-developed-by.
sure, will fix the incorrect usage of tags in the next version.

> > Fixes: 02c057ddefef ("ACPI: video: Convert the driver to a platform one")
> > Signed-off-by: Pratap Nirujogi <pratap.nirujogi@xxxxxxx>
>
> ...
>
> >        i2c_dw_prepare_clk(i_dev, true);
> > -     i2c_dw_init(i_dev);
> > +
> > +     /* Skip i2c_dw_init if regmap not yet created by i2c_dw_probe */
>
> Use same style for references to the functions: func().
sure, will fix it in the next version.

> > +     if (i_dev->map)
> > +             i2c_dw_init(i_dev);
>
> TBH, Looks like papering over the problem. Why the resume is called on
> uninitialised regmap to begin with?
yes, I agree, this change avoids the issue rather than fixing the root 
cause of the race condition. I investigated further and shared the 
details in response to Mario’s comments. Could you please review the 
latest response[1] and share your feedback?

[1] 
https://lore.kernel.org/all/61dbe8a1-6578-4690-8571-6b00c1850d34@xxxxxxx/

Thanks,
Pratap


> --
> With Best Regards,
> Andy Shevchenko