[U-Boot] [PATCH 068/126] x86: tpl: Add a fake PCI bus

[Bin Meng]

Hi Simon,

On Wed, Sep 25, 2019 at 10:58 PM 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 (manual mode, fake PCI bus)
>    SPL    - CONFIG_SPL_PCI is set (manual mode but with real PCI bus)

manual mode is confusing. Maybe (no auto-config, real PCI bus)?

>    U-Boot - CONFIG_PCI is set (full auto-config after relocation)
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  arch/x86/lib/tpl.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/arch/x86/lib/tpl.c b/arch/x86/lib/tpl.c
> index d70f590541c..f8075568a2c 100644
> --- a/arch/x86/lib/tpl.c
> +++ b/arch/x86/lib/tpl.c
> @@ -5,6 +5,7 @@
>
>  #include <common.h>
>  #include <debug_uart.h>
> +#include <dm.h>
>  #include <spl.h>
>  #include <asm/cpu.h>
>  #include <asm/mtrr.h>
> @@ -115,3 +116,27 @@ void spl_board_init(void)
>  {
>         preloader_console_init();
>  }
> +
> +#if !CONFIG_IS_ENABLED(PCI)
> +/*
> + * This is a fake PCI bus for TPL when it doesn't have proper PCI. It is enough
> + * to bind the devices on the PCI bus, some of which have early-regs properties
> + * providing fixed BARs. Individual drivers program these BARs themselves so
> + * that they can access the devices. The BARs are allocated statically in the
> + * device tree.
> + *
> + * Once SPL is running it enables PCI properly, but does not auto-assign BARs
> + * for devices, so the TPL BARs continue to be used. Once U-Boot starts it does
> + * the autoallocation (after relocation).

missing space between "auto" and "allocation"

> + */
> +static const struct udevice_id tpl_fake_pci_ids[] = {
> +       { .compatible = "pci-x86" },
> +       { }
> +};
> +
> +U_BOOT_DRIVER(pci_x86) = {
> +       .name   = "pci_x86",
> +       .id     = UCLASS_SIMPLE_BUS,
> +       .of_match = tpl_fake_pci_ids,
> +};
> +#endif
> --

Regards,
Bin