A missing or empty dma-ranges in a DT node implies a 1:1 mapping for dma
translations. In this specific case, the current behaviour is to zero out
the entire specifier so that the translation could be carried on as an
offset from zero.  This includes address specifier that has flags (e.g.
PCI ranges).
Once the flags portion has been zeroed, the translation chain is broken
since the mapping functions will check the upcoming address specifier
against mismatching flags, always failing the 1:1 mapping and its entire
purpose of always succeeding.
Set to zero only the address portion while passing the flags through.

Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
---
This patch still lacks an entry in the DT unittest.

 drivers/of/address.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 286f0c161e33..72b6accff21c 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -455,7 +455,8 @@ static int of_translate_one(struct device_node *parent, struct of_bus *bus,
 	}
 	if (ranges == NULL || rlen == 0) {
 		offset = of_read_number(addr, na);
-		memset(addr, 0, pna * 4);
+		/* copy the address while preserving the flags */
+		memset(addr + pbus->flag_cells, 0, (pna - pbus->flag_cells) * 4);
 		pr_debug("empty ranges; 1:1 translation\n");
 		goto finish;
 	}
-- 
2.35.3