BBB Framebuffer : Need Ideas.

[Vijay Kumar Banerjee]

On Thu, Jul 11, 2019 at 12:51 AM Christian Mauderer <list at c-mauderer.de>
wrote:

> On 10/07/2019 12:53, Christian Mauderer wrote:
> >
> >
> > On 10/07/2019 12:38, Vijay Kumar Banerjee wrote:
> >>
> >>
> >> On Wed, Jul 10, 2019 at 12:40 PM Christian Mauderer
> >> <christian.mauderer at embedded-brains.de
> >> <mailto:christian.mauderer at embedded-brains.de>> wrote:
> >>
> >>     On 09/07/2019 21:13, Vijay Kumar Banerjee wrote:
> >>     > Hello all,
> >>     >
> >>     > First the status :
> >>     > * The fbd has been ported and it's attaching with the fb0 devie.
> >>     There's
> >>     >    an fb0 device entry created.
> >>     > * In the following commit I have added mmap to libbsd. This works
> >>     like a
> >>     > wrapper to the mmap in cpukit
> >>     >
> >>     :
> https://github.com/thelunatic/rtems-libbsd/commit/a8fc3b2b6840465029a000cc4169e9efbd551097
> >>     >
> >>     > Blocker :
> >>     > * After the fb0 is created and mmap is added, I don't see
> anything on
> >>     >   the screen. From the FreeBSD, it seemed like the VT driver is
> needed
> >>     > and that is responsible for turning on the screen. So I have
> ported a
> >>     > minimal version of the VT with only the initialization and
> >>     allocate parts:
> >>     >
> >>
> https://github.com/thelunatic/rtems-libbsd/commit/95279e116717973525b581ae2e9550d1d3b8e1ba
> >>     >
> >>     > But even after porting the VT driver which initializes well ( As
> the
> >>     > message during booting says). I don't see anything on the screen.
> >>     > I need some ideas on what is missing or how to debug this.
> >>     >
> >>     > The app I'm using to test framebuffer is pushed here :
> >>     >
> https://github.com/thelunatic/rtems-bbb/tree/master/apps/fb-sample
> >>     >
> >>     > Any idea regarding this is greatly appreciated.
> >>     >
> >>     > Thanks,
> >>     > Vijay
> >>     >
> >>
> >>     Hello Vijay,
> >>
> >>     did you have a look at the SPI of the HDMI framer? What is it used
> for
> >>     according to the data sheet? Is it necessary for the driver?
> >>
> >> Hi,
> >> From the datasheet, it seems that the SPI1_CS0 and SPI1_D0 pins are
> >> configured as I2S interface for the audio. I think this is not
> necessary
> >> and it is enabled only for a few selected resolutions that support
> audio.
> >>
> >>     From our chat discussions and my own tests I know that the screen is
> >>     still not receiving a signal. So I would assume some quite basic
> >>     problem. If your new mmap wouldn't work, you should still get at
> least a
> >>     black screen.
> >>
> >> I was also hoping that VT will do the initialization and turn the
> screen On.
> >> There might be something useful that I omitted during the porting. If
> you
> >> can please review the commit, I can send it in the devel.
> >
> > I think in this case it's enough on your github repo.
> >
> > I haven't found anything yet. I'll try to have a more detailed look as
> > soon as possible. But I'll be busy with some other topics today
> > (including the evening). So most likely I can't tell much till tomorrow.
> >
> > You might want to have a look whether you find some documentation for
> > the graphics IP core in the TI chip. It could be interesting to have
> > some documentation to see the basic steps. Maybe this gives a hint. An
> > alternative could be to look at some other drivers (Linux, maybe U-Boot
> > or some embedded systems if there is one) to find out something more.
> > There should be some sequence for the setup. If you know that sequence
> > you can try to find it in the libbsd driver and see whether all steps
> > are done.
> >
>
> Although I don't have put much time into it today I had a look at the
> original commit that added the FreeBSD am335x_lcd driver:
> 8cfe669b84fdbf7d9f1312c50c39b663d68be85c
>
> The author added not only am335x_lcd.c but am335x_lcd_syscons.c too.
> From a look at it, most of it is a system console (like the name
> suggests) and won't be useful for the current step. But the syscons_init
> caught my eye:
>
> There is a call to vid_register in it. This function is declared in
> sys/dev/fb/fbreg.h and defined in sys/dev/fb/fb.c. According to the
> comment in the c file it "Registers a video adapter". I haven't seen a
> call to that function in the ported code.
>
> I have imported the file but I can't reach any am335x_syscons* functions
from the debugger. The am335x_syscons_configure is supposed to call
the init function which calls the vid_register. The am335x_syscons creates
a DATA_SET with the macro VIDEO_DRIVER with the configure function.
Is it supposed to be linked somewhere that I'm missing?

> So maybe it would be worth a try to port the lcd_syscons.c too. Maybe
> even instead of the (not working) VT driver. Like for the VT, you most
> likely can just remove everything that's console related in case it
> makes problems. The relevant function should be syscons_init.
>
> Best regards
>
> Christian
>
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