Re: [edk2-devel] [PATCH 1/1] EmbeddedPkg/NonCoherentIoMmuDxe: Make SetAttributes always succeed

["Leif Lindholm" <quic_llindhol@quicinc.com>]

On 2024-03-12 08:17, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> NonCoherentIoMmuSetAttribute() does nothing except return
> EFI_UNSUPPORTED. This was fine when it was introduced, but now, the PCI
> bus driver will fail a PCI I/O Map() operation if the SetAttributes
> fails.
> 
> So return EFI_SUCCESS instead.

It's unclear to me why this change is safe (looking forward).
Does NonCoherentIoMmuDxe also imply no IoMmu actually exists?

/
     Leif

> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> This fixes a regression on Raspberry Pi4, which no longer boots.
> 
>   EmbeddedPkg/Drivers/NonCoherentIoMmuDxe/NonCoherentIoMmuDxe.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/EmbeddedPkg/Drivers/NonCoherentIoMmuDxe/NonCoherentIoMmuDxe.c b/EmbeddedPkg/Drivers/NonCoherentIoMmuDxe/NonCoherentIoMmuDxe.c
> index 4e7a5698c162..f02a76a62ea8 100644
> --- a/EmbeddedPkg/Drivers/NonCoherentIoMmuDxe/NonCoherentIoMmuDxe.c
> +++ b/EmbeddedPkg/Drivers/NonCoherentIoMmuDxe/NonCoherentIoMmuDxe.c
> @@ -70,7 +70,7 @@ NonCoherentIoMmuSetAttribute (
>     IN UINT64                IoMmuAccess
>     )
>   {
> -  return EFI_UNSUPPORTED;
> +  return EFI_SUCCESS;
>   }
>   
>   /**



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