PCI: dwc: Simplify unrolled iATU detection

The unrolled version of the internal ATU has been available since the DWC
PCIe v4.80a IP core, but it may not be enabled.  Per [1], if unrolled ATU
is enabled, the PCIE_ATU_VIEWPORT does not exist and reads as 0xffffffff;
while if unrolled ATU is disabled, PCIE_ATU_VIEWPORT will contain some
zeros.

Simplify dw_pcie_iatu_unroll_enabled() by checking the value of
PCIE_ATU_VIEWPORT.

[1] DesignWare Cores, PCI Express Controller, Register Desciptions,
v.4.90a, December 2016, p.855

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/[email protected]
Tested-by: Manivannan Sadhasivam <[email protected]>
Signed-off-by: Serge Semin <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Reviewed-by: Rob Herring <[email protected]>

0 files changed, 0 insertions, 0 deletions