Question regarding framebuffer driver.

[Oleksandr Tymoshenko]

Vijay Kumar Banerjee (vijaykumar9597 at gmail.com) wrote:
> Hello everyone,
> 
> I'm working on porting the framebuffer driver to RTEMS with Beaglebone
> Black as the target device. I have have already ported the am335x_lcd,
> tda19988, fbd and VT drivers, but the screen doesn't seem to "power up".
> >From the FreeBSD bootlog (12-RELEASE), I see that the screen is
> turning on after the VT initialization message, so I guess it's something
> that happens after the vt initialization that turns the screen on.
> 
> So far I have ported the vt_fb and vt_core and it boots up well with the
> message :
> VT: initialize with new VT driver "fb".
> 
> But the screen doesn't seem to turn on. Can someone please tell me
> or point me to the right place in the code that is responsible for turning
> the
> screen on after VT initialization?
 

Hi Vijay,

Because the code is ported to another OS there are too many ways things
can go wrong. The problem can be in VT, in am335x_lcd or in TDA driver
so it's hard to pinpoint exact location. If I was to debug such problem
I'd try to isolate each driver and make sure it works on its own. I think
the easiest way is to get LCD screen that connects directly to AM335x,
without HDMI framer and try to initialize framebuffer in am335x_lcd
driver with certain pattern to make sure it works. FreeBSD driver worked
with 4DCAPE [1] at some point, so it might be a good start. Once you
make sure am335x_lcd driver works, you can verify TDA driver with some
hardcoded logic that doesn't require VT layer and once both are known
to work - it's only VT layer to debug.

[1] https://4dsystems.com.au/gen4-4dcape-43t

-- 
gonzo