[U-Boot] [RFC] Migrating iMX LCDIF drivers to Driver Model

[Igor Opaniuk]

Hi Jagan,

On Tue, Apr 16, 2019 at 2:35 PM Jagan Teki <jagan at amarulasolutions.com> wrote:
>
> On Tue, Apr 16, 2019 at 5:36 PM Igor Opaniuk <igor.opaniuk at toradex.com> wrote:
> >
> > Marek, Peng,
> >
> > Writing to you as you were the main contributors to U-boot mxsfb
> > driver implementation (i.MX23/i.MX28 LCDIF driver).
> >
> > I was about to start working on it's migration to DM (currently mxsfb
> > is being used on our SoM Colibri iMX7S/D), but found it a bit
> > out-dated (no one introduced any changes for the last 5 years) and
> > maybe it's really does make a sense to fetch and port the latest one
> > from the Linux mainline (in a sake of avoiding divergence in
> > implementation and continue fetching future updates from the Linux
> > kernel).
> >
> > So there are 2 questions spinning in my mind:
> > 1) In case if you are maybe aware, if there were any intentions to do
> > this migration before?  (maybe someone asked similar questions or even
> > send some patches, but didn't manage to upstream that; or did similar
> > stuff in some downstream U-boot forks, whatever). Unfortunately I
> > can't any information regarding this in U-boot ML archives .
> >
> > 2) Will it be OK if I introduce a brand new mxsfb driver (ported from
> > Linux), which will be used only when U-boot is built with
> > CONFIG_DM_VIDEO enabled? Existing mxsfb will be left as it is, so I
> > can be removed easily when full migration to DM is done for all boards
> > that are using this driver.
>
> How about keeping common code aside and make the existing driver to
> support dm and non-dm. We can take the required changes on top of dm
> code if possible, this would be prominent transition instead of having
> separate code base.

Actually this is what I started doing in the very begging, but the
thing is that current mxsfb driver should be fully re-implemented to
make it possible.
Taking into account that there is already a pretty high divergence
between the one in U-boot and another in Linux, I think it's better to
sync with the existing mxsfb inthen  Linux kernel instead of spending
twice much effort on supporting two different implementations in the
future.

Anyway legacy stuff supposed to be removed ASAP (when migration is
finished), so I really would like to keep the old implementation
aside.


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Senior Development Engineer,
Igor Opaniuk

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