[edk2-devel] [PATCH edk2-platforms] Platform/OverdriveBoard: work around network ConnectAll() dependency

[Ard Biesheuvel]

On 6/1/20 3:19 PM, Leif Lindholm wrote:
> On Fri, May 29, 2020 at 23:40:19 +0200, Ard Biesheuvel wrote:
>> The AMD Seattle based platforms have been kept up to date in recent
>> years, even though the hardware is obsolete and was never available
>> that widely in the first place.
>>
>> However, one aspect that has sadly been left behind is the support for
>> the builtin network controllers. These are only wired up and enabled
>> on the Overdrive board to begin with, and the driver was only made
>> available as two separate binary blobs implementing the SNP protocol
>> for each controller separately, without taking the UEFI driver model
>> into account.
>>
>> Even worse, the PHY initialization code that needs to run at boot in
>> order for the OS to be able to use the device never executes unless
>> the upper networking layers start the SNP protocol, which doesn't
>> happen on a fast boot (one that does not use ConnectAll()) unless the
>> boot target is a network device path.
>>
>> We cannot fix the driver, but fortunately, there is another way out:
>> protocols that are installed on a handle during the execution of the
>> entrypoint of a driver will be connected by the DXE core, and so we
>> can ensure that the old behavior is retained regardless of whether
>> ConnectAll() is ever invoked, by reordering the load sequence so that
>> the upper layer drivers have all been registered by the time the
>> entrypoints of the SNP drivers are called.
>>
>> This relies on FV contents to be dispatched in the order they appear
>> in the .FDF file. The AMD SNP driver as well as the upper layer
>> drivers in NetworkPkg are UEFI_DRIVER modules, which means their
>> DEPEXes are implicitly defined as the full set of architectural
>> PI protocols. This means that all these modules become available for
>> dispatch at the same time, and their dispatch order is fully defined
>> by the order of appearance in the FV. Unfortunately, this is an
>> implementation detail rather than something that is supported by the
>> PI spec, but this is unlikely to ever change since other platforms
>> undoubtedly exist that depend on this behavior as well.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at arm.com>
> 
> I'm holding my nose a bit, but:
> Reviewed-by: Leif Lindholm <leif at nuviainc.com>
> 


I know :-)

Pushed as 747eeac8a8b9..608d71ec9396

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