Re: [edk2-platforms PATCH 3/6] Marvell: Armada7k8kPciHostBridgeLib: Remove ECAM base limitation

["Ard Biesheuvel" <ardb@kernel.org>]

On Mon, 2 Aug 2021 at 07:01, Marcin Wojtas <mw@semihalf.com> wrote:
>
> On CN913x-based platforms it is possible to have up to 9 PCIE
> root complexes. In such case it may be necessary to configure
> more configuration spaces with smaller bus count, so that
> to fit the memory layout constraints. For that purpose remove
> forcing ECAM base to be divisible by SIZE_256MB.
>

There is one subtlety here that we need to take into account: IIUC,
PCIe requires that the ECAM start address of bus N equals N MB modulo
256 MB. In other words, if your ECAM range lives at 1 GB + 128 MB, the
bus range has to start at bus 128.

I think OSes are usually quite lax about this, but it is something to
double check regardless, even for existing platforms


> Signed-off-by: Marcin Wojtas <mw@semihalf.com>
> ---
>  Silicon/Marvell/Armada7k8k/Library/Armada7k8kPciHostBridgeLib/PciHostBridgeLibConstructor.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/Silicon/Marvell/Armada7k8k/Library/Armada7k8kPciHostBridgeLib/PciHostBridgeLibConstructor.c b/Silicon/Marvell/Armada7k8k/Library/Armada7k8kPciHostBridgeLib/PciHostBridgeLibConstructor.c
> index 067e57a2dc..87e57aeae3 100644
> --- a/Silicon/Marvell/Armada7k8k/Library/Armada7k8kPciHostBridgeLib/PciHostBridgeLibConstructor.c
> +++ b/Silicon/Marvell/Armada7k8k/Library/Armada7k8kPciHostBridgeLib/PciHostBridgeLibConstructor.c
> @@ -219,7 +219,6 @@ Armada7k8kPciHostBridgeLibConstructor (
>      PcieController = &(BoardPcieDescription->PcieControllers[Index]);
>
>      ASSERT (PcieController->PcieBusMin == 0);
> -    ASSERT (PcieController->ConfigSpaceAddress % SIZE_256MB == 0);
>
>      if (PcieController->HaveResetGpio == TRUE) {
>        /* Reset PCIE slot */
> --
> 2.29.0
>