[U-Boot] [PATCH v3 025/108] x86: tpl: Add a fake PCI bus

[Andy Shevchenko]

On Mon, Oct 21, 2019 at 7:24 AM Simon Glass <sjg at chromium.org> wrote:
>
> In TPL we try to minimise code size so do not include the PCI subsystem.
> We can use fixed BARs and drivers can directly program the devices that
> they need.
>
> However we do need to bind the devices on the PCI bus and without PCI this
> does not ordinarily happen. As a work-around, define a fake PCI bus which
> does this binding, but no other PCI operations. This is a convenient way
> to ensure that we can use the same device tree for TPL, SPL and U-Boot
> proper:
>
>    TPL    - CONFIG_TPL_PCI is not set (no auto-config, fake PCI bus)
>    SPL    - CONFIG_SPL_PCI is set (no auto-config but with real PCI bus)
>    U-Boot - CONFIG_PCI is set (full auto-config after relocation)

PCI(e) bus is present in a lot of SoCs (not exclusively x86). Perhaps
better idea is to have something like lib/pci.c with minimum support
for PCI type 1 and probably PCI type 2 accessors and other very basic
functions.

-- 
With Best Regards,
Andy Shevchenko