[PATCH v2 1/2] of: addr: Translate 'dma-ranges' for parent nodes missing 'dma-ranges'

[Bin Meng]

'dma-ranges' frequently exists without parent nodes having 'dma-ranges'.
While this is an error for 'ranges', this is fine because DMA capable
devices always have a translatable DMA address. Also, with no
'dma-ranges' at all, the assumption is that DMA addresses are 1:1 with
no restrictions unless perhaps the device itself has implicit
restrictions.

This keeps in sync with Linux kernel commit:

  81db12ee15cb: of/address: Translate 'dma-ranges' for parent nodes missing 'dma-ranges'

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
Reviewed-by: Simon Glass <sjg at chromium.org>

---

Changes in v2:
- rebase on top of Dario's revert patch:
  http://patchwork.ozlabs.org/project/uboot/patch/20210425141746.19115-6-dariobin@libero.it/
- drop commit "of: addr: Abort address translation for parent nodes missing 'ranges'",
  as the revert patch restores the abort behavior

 drivers/core/of_addr.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/core/of_addr.c b/drivers/core/of_addr.c
index 9b77308182..a3af48fd88 100644
--- a/drivers/core/of_addr.c
+++ b/drivers/core/of_addr.c
@@ -192,9 +192,13 @@ static int of_translate_one(const struct device_node *parent,
 	 *
 	 * As far as we know, this damage only exists on Apple machines, so
 	 * This code is only enabled on powerpc. --gcl
+	 *
+	 * This quirk also applies for 'dma-ranges' which frequently exist in
+	 * child nodes without 'dma-ranges' in the parent nodes. --RobH
 	 */
 	ranges = of_get_property(parent, rprop, &rlen);
-	if (ranges == NULL && !of_empty_ranges_quirk(parent)) {
+	if (ranges == NULL && !of_empty_ranges_quirk(parent) &&
+	    strcmp(rprop, "dma-ranges")) {
 		debug("no ranges; cannot translate\n");
 		return 1;
 	}
-- 
2.25.1