Re: [PATCH 1/2] PCI: dwc: Allow drivers to skip MEM outbound iATU setup

[Xincheng Zhang]

Hi Mani,

On Wed, Sep 02, 2026 at 04:18:58PM +0200, Manivannan Sadhasivam wrote:
> Can you elaborate why the outbound iATU mapping is not required? Are they using
> ECAM or some other custom mapping scheme?

DP1000 is not using ECAM for this controller. Config space accesses still
use the DWC own config access path, so CFG accesses continue to use the
normal DWC outbound iATU programming for CFG0/CFG1.

The bypass is only for host bridge MEM windows. The DP1000 integration has
SoC wrapper address decode for the PCIe MEM apertures described by the
"ranges" property. CPU physical accesses to those MEM apertures are routed
directly as PCIe MEM transactions with the corresponding PCIe bus address,
without consuming outbound iATU windows.

I/O space is also unchanged and still uses an outbound iATU window. So the
new flag only skips generic MEM-window programming; it does not change CFG
or I/O iATU setup.

This direct MEM path has been verified on DP1000 EVB and Titan with large
BAR MMIO read/write tests.

I will make this clearer in v2 by updating the commit messages/comments to
say that the bypass is MEM-only, not ECAM, and that CFG/I/O iATU setup is
unchanged.

Thanks,
Xincheng