Re: [PATCH] powerpc: isa-bridge: Fix ISA mmapping when "ranges" is not present

Commit e4ab08be5b49 ("powerpc/isa-bridge: Remove open coded "ranges"
parsing") broke PASemi Nemo board booting. The issue is the ISA I/O
range was not getting mapped as the logic to handle no "ranges" was
inverted. If phb_io_base_phys is non-zero, then the ISA range defaults
to the first 64K of the PCI I/O space. phb_io_base_phys should only be 0
when looking for a non-PCI ISA region.

Fixes: e4ab08be5b49 ("powerpc/isa-bridge: Remove open coded "ranges" parsing")
Link: https://lore.kernel.org/all/301595ad-0edf-2113-b55f-f5b8051ed24c@xenosoft.de/ (local)
Reported-by: Christian Zigotzky <redacted>
Signed-off-by: Rob Herring <robh@kernel.org>
---
Untested, but I think this should fix the issue.

  arch/powerpc/kernel/isa-bridge.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/isa-bridge.c b/arch/powerpc/kernel/isa-bridge.c
index 85bdd7d3652f..48e0eaf1ad61 100644
--- a/arch/powerpc/kernel/isa-bridge.c
+++ b/arch/powerpc/kernel/isa-bridge.c

@@ -93,11 +93,12 @@ static int process_ISA_OF_ranges(struct device_node *isa_node,
  	}
  
  inval_range:
-	if (!phb_io_base_phys) {
+	if (phb_io_base_phys) {
  		pr_err("no ISA IO ranges or unexpected isa range, mapping 64k\n");
  		remap_isa_base(phb_io_base_phys, 0x10000);
+		return 0;
  	}
-	return 0;
+	return -EINVAL;
  }