[U-Boot] [PATCH 4/5] x86: efi-x86_payload: Enumerate PCI bus during early boot

[Bin Meng <bmeng.cn@gmail.com>]

Hi Simon,

On Thu, Jun 21, 2018 at 1:51 AM, Simon Glass <sjg@chromium.org> wrote:
> Hi Bin,
>
> On 17 June 2018 at 06:57, Bin Meng <bmeng.cn@gmail.com> wrote:
>> The generic efi payload currently does not enumerate the PCI bus,
>> which means peripherals on the PCI bus are not discovered by their
>> drivers. This uses board_early_init_r() to do the PCI enumeration.
>>
>> Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
>> ---
>>
>>  board/efi/efi-x86_payload/Kconfig   |  1 +
>>  board/efi/efi-x86_payload/Makefile  |  2 +-
>>  board/efi/efi-x86_payload/payload.c | 18 ++++++++++++++++++
>>  3 files changed, 20 insertions(+), 1 deletion(-)
>>  create mode 100644 board/efi/efi-x86_payload/payload.c
>
> I would like to consider adding a mechanism to indicate that a uclass
> should be inited (and its devices probed) on startup. This would be
> used for things which provide essential peripherals, which otherwise
> would not be visible in the initial driver-model bind process.
>

Good to know!

> I am not sure whether this should be:
>
> - a flag in the uclass

Only adding a flag to the uclass driver seems not working. On some
systems like x86 UCLASS_PCI may be init at boot up, but on other
systems this might not be the case. So we need find a place to tell DM
to init the uclass driver if the uclass driver has the flag, but
where?

> - a flag in the BOARD driver (assuming we have a BOARD uclass soon)

The concept of BOARD driver sounds interesting. So does the BOARD
uclass driver intend to replace various config options like
CONFIG_BOARD_EARLY_INIT_F, CONFIG_BOARD_EARLY_INIT_R,
CONFIG_BOARD_LATE_INIT, etc? If we do that, how do we guarantee the
init order with other components in board_f.c and board_r.c?

> - a function call into DM

Like uclass_first_device()?

> - something else
>
> But I think it is justified in the case of PCI, since some systems
> cannot find all their devices without scanning it.
>

Yes, this makes sense for PCI on x86.

> What do you think?
>

Regards,
Bin