Re: drm: mipi_dbi_hw_reset() keeps display in reset

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On Sat, Feb 15, 2025 at 02:14:54PM -0500, Alex Lanzano wrote:
> On Fri, Feb 14, 2025 at 08:04:41PM -0500, Alex Lanzano wrote:
> > On Fri, Feb 14, 2025 at 10:29:29AM +0100, Josef Luštický wrote:
> > > Hello Alex,
> > > there is a bug in mipi_dbi_hw_reset() function that implements the logic of
> > > display reset contrary.
> > > It keeps the reset line activated which keeps displays in reset state.
> > > 
> > > I reported the bug to
> > > https://gitlab.freedesktop.org/drm/misc/kernel/-/issues/63
> > > 
> > > Unfortunately, fixing the bug would mean current DTB-ABI breakage and
> > > device-trees modification would be needed.
> > > I mainly write this email to let you and other people know about it, so
> > > hopefully it can be found easier.
> > > What are your thoughts?
> > Thanks for making me aware. I'll dig into over the weekend and get back
> > to you
> 
> Alright so I looked into a bit more. Looks like the MIPI Specification
> says that the reset line is active low. So, if we want dt entries to be
> correct the logic for setting the reset line in mipi_dbi_hw_reset()
> should be flipped. However, like you said, this is going to cause a some
> confused developers to break out their oscilloscopes to figure out
> why their display isn't working.

Would it be easier to flip GPIO flag in DT (and explicitly document that
the flag is to be inverted)?

-- 
With best wishes
Dmitry



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