linux-kernel - [PATCH 10/11] of/address: Translate 'dma-ranges' for parent nodes missing 'dma-ranges'

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Message-Id: <20190927002455.13169-11-robh@kernel.org>
Date:   Thu, 26 Sep 2019 19:24:54 -0500
From:   Rob Herring <robh@...nel.org>
To:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Robin Murphy <robin.murphy@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Stefan Wahren <wahrenst@....net>,
        Frank Rowand <frowand.list@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Marek Vasut <marek.vasut@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms+renesas@...ge.net.au>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Oza Pawandeep <oza.oza@...adcom.com>
Subject: [PATCH 10/11] of/address: Translate 'dma-ranges' for parent nodes missing 'dma-ranges'

'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.

Cc: Robin Murphy <robin.murphy@....com>
Signed-off-by: Rob Herring <robh@...nel.org>
---
 drivers/of/address.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index e918001c7798..5b835d332709 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -519,9 +519,13 @@ static int of_translate_one(struct device_node *parent, struct of_bus *bus,
 	 *
 	 * 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")) {
 		pr_debug("no ranges; cannot translate\n");
 		return 1;
 	}
-- 
2.20.1