Minimal GPU setup

[Amol]

Thank you Alex.

On 07/02/2022, Deucher, Alexander <Alexander.Deucher at amd.com> wrote:
> [AMD Official Use Only]
>
> Most of the register programming in evergreen_gpu_init is required.  That
> code handles things like harvesting (e.g., disabling bad hardware resources)
> and setting sane asic specific settings in some registers.  If you don't do
> it, work may get scheduled to bad or incorrectly configured hardware blocks
> which will lead to hangs or corrupted results.  You can probably skip some
> of them, but I don't remember what is minimally required off hand.  It's
> generally a good idea to re-initialize those registers anyway in case
> someone has previously messed with them (e.g., manual register munging or
> GPU passed through to a VM etc.).

Understood.

>
> Posting the bios is enough to get you a working memory controller and enough
> asic setup to light up displays (basically what you need for pre-OS
> console).  As Christian mentioned, loading the ucodes will get the
> associated engines working so that you can start feeding commands to the
> GPU, but without proper configuration of the various hardware blocks on the
> GPU, you may not have success in feeding data to the GPU.

Understood. I think I wanted a confirmation that the steps I took so far are not
completely incorrect and may be just enough to see some GPU activity,
before I spend more effort programming other blocks. The feedback and a small
but working test helps restore the motivation.

Thanks,
Amol

>
> Alex
>
>
> ________________________________
> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Amol
> <suratiamol at gmail.com>
> Sent: Saturday, February 5, 2022 4:47 AM
> To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
> Subject: Minimal GPU setup
>
> 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.
>
> 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.)?
>
> Thanks,
> Amol
>