Hi Amol,
Am 05.02.22 um 10:47 schrieb Amol:
Hello,
I am learning to program Radeon HD 7350 by reading the radeon
driver source in Linux, and the guides/manuals from AMD.
I understand the general flow of initialization the driver performs. I
have also been able to understand and re-implement the ATOM
BIOS virtual machine.
That sounds like you already came pretty far.
I am trying to program the device up from scratch (i.e. bare-metal).
Do I need to perform all those steps that the driver does? Reading
the evergreen_gpu_init function is demotivating; it initializes many
fields and registers which I suspect may not be required for a minimal
setup.
Is posting the BIOS and loading the microcode enough to get me started
with running basic tasks (DMA transfers, simple packet processing, etc.)?
Well yes and no. As bare minimum you need the following:
1. Firmware loading
2. Memory management
3. Ring buffer setup
4. Hardware initialization
When that is done you can write commands into the ring buffers of the CP
or SDMA and see if they are executed (see the *_ring_test() functions in
the driver). SDMA is usually easier to get working.
When you got that working you can worry about IB (indirect buffers)
which are basically subroutines calls written into the ring buffers.
Most commands (like copy from A to B, fill something, write value X to
memory or write X into register Y) can be used from the ring buffers
directly, but IIRC some context switching commands which are part of the
rendering process require special handling.
But keep in mind that all of this will just be horrible slow because the
ASIC runs with the bootup clocks which are something like 100Mhz or even
only 17Mhz on very old models. To change that you need to implement
power management, interrupt handling etc etc....
Good luck,
Christian.
Thanks,
Amol
