[RPI BSP] Framebuffer test

[Pavel Pisa]

Hello QIAO YANG,

I have found that I have not succeed to find time to reply to this one.
I have not any more founded resolution to these.

On Tuesday 07 of April 2015 22:55:07 QIAO YANG wrote:
> On Apr 07, 2015, at 06:50 AM, Pavel Pisa <ppisa4lists at pikron.com> wrote:
> > ARMV7_MMU_DATA_READ_WRITE
> >
> > at least for start. Some performance can be gained if read caching
> > and write through + write combine is enabled for framebuffer area,
> > but I am not sure if there is defined matching CP15 combination
> > in
>
> I have got it work after setting the MMU. Thanks!

Good work.

> > rtems/c/src/lib/libcpu/arm/shared/include/arm-cp15.h
> >
> > If this matches then you should be able to access framebuffer directly.
> > I.e. from some BSP/framebuffer driver initialization code or some
> > application linked to RTEMS system libraries some or you can modify some
> > RTEMS test example to access given address directly.
> >
> > Which pixel format are you using - 16 bit RGB565, 24 bit RGB888
> > or 32 bit RGBA8888? I would suggest to use 32 bit format RGB + 8 bit
> > padding when there is enough memory for simplicity. It allows simple
> > XY to address conversion and accesses to pixel are aligned.
>
> In fact, for the moment, I'm using 16bit RGBA for display. As for the
> memory, rpi A has 256MB, rpi B  has 512MB, and rpi2 has 1GB. I'm not as
> experience to tell which format would be better but I'll consider that. Is
> there any kernel configuration that would let user to determine the memory
> for GPU(it's like the memory split on wheezy)?

It depends mainly one memory size (which is not scare resource on RPi when
compared to other embedded systems). I would suggest 32 bit RGBA or in
the fact RGB+spare byte. It is nice to compute X position to address
by multiple by 4 (shift 2 left) and access each point at aligned address
by word size instruction. Probably fastest on ARM. But it is not critical.
16-bit is OK.

> > Then I suggest to test Microwindows to paint some more interesting
> > image on the screen.
>
> I guess you've got my reply on the email, gtk building. It's weird that all
> libraries are installed successfully, but the compiler still complain about
> library missing. Do you have any idea what might be the problem? I'll try
> to compile some samples without the build scripts later.

I do not know where a problem is. Probably (even for me) the fastest is
to try to build RTEMS and graphic toolkit for RPi on my computer and try
to find where problem can be. Please send instruction and pointer to GITs
which hold actual code.

But I (unfortunatelly) cannot promiss that I found time for that
in next two weeks.

Best wishes,

             Pavel