Re: [PATCH v5 4/4] drm: bridge: ti-sn65dsi83: Add error recovery mechanism

Alexander Stein
2025-02-10T10:42:28Z

Hi Herve,

Am Freitag, 7. Februar 2025, 19:08:16 CET schrieb Herve Codina:
> Hi Alexander,
>
> On Thu, 06 Feb 2025 16:39:09 +0100
> Alexander Stein <alexander.stein@ew.tq-group.com> wrote:
>
> > Hi Herve,
> >
> > Am Donnerstag, 6. Februar 2025, 16:20:48 CET schrieb Herve Codina:
> > > Hi Alexander,
> > >
> > > On Thu, 06 Feb 2025 15:38:42 +0100
> > > Alexander Stein <alexander.stein@ew.tq-group.com> wrote:
> > >
> > > ...
> > > > With interrupt configured I got the following stack trace upon
> > > > reboot/poweroff:
> > > >
> > > > [ 91.317264] sn65dsi83 2-002d: reset the pipe
> > > > [ 91.344093] Unable to handle ke
> > > > ** replaying previous printk message **
> > > > [ 91.344093] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > > ...
> > >
> > > Ouch :(
> > >
> > > One question to help me investigating:
> > > Do you have the issue at init/probe or when you start to display graphics?
> >
> > This is during shutdown/poweroff. I assume that regmap_reg() in
> > sn65dsi83_handle_errors() fails and because of that reset_work is scheduled.
> >
>
> Found the issue.
>
> Can you give me following information so that I can validate what I
> understood:
> - Is your interrupt line connected directly to the SoC?

No, unfortunately not. It's connected to a GPIO expander, which in turn
delivers an IRQ to the SoC. In between the bridge and the expander is a
buffer for voltage switch (1V8 -> 3V3).

> - Is there any pullup/pulldown on your interrupt line?

As far a I can tell, there is no pullup/pulldown on the IRQ line to
the buffer.

> - In your devicetree what is the configuration used for this interrupt in
> terms of level or edge.

As this line is connected to an expander (pca9555) only edge triggered
interrupts are supported.

> Anyway, I will send a fix in the next iteration.

Thanks for digging into this.
Best regards,
Alexander
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