linux-kernel - [PATCH] of/address: Return an error when no valid dma-ranges are found

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Message-Id: <20230126-synquacer-boot-v1-1-94ed0eb1011f@kernel.org>
Date:   Thu, 26 Jan 2023 16:26:39 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Luca Di Stefano <luca.distefano@...aro.org>,
        993612@...s.debian.org, stable@...nel.org
Subject: [PATCH] of/address: Return an error when no valid dma-ranges are
 found

Commit 7a8b64d17e35 ("of/address: use range parser for of_dma_get_range")
converted the parsing of dma-range properties to use code shared with the
PCI range parser. The intent was to introduce no functional changes however
in the case where we fail to translate the first resource instead of
returning -EINVAL the new code we return 0. Restore the previous behaviour
by returning an error if we find no valid ranges, the original code only
handled the first range but subsequently support for parsing all supplied
ranges was added.

This avoids confusing code using the parsed ranges which doesn't expect to
successfully parse ranges but have only a list terminator returned, this
fixes breakage with so far as I can tell all DMA for on SoC devices on the
Socionext Synquacer platform which has a firmware supplied DT. A bisect
identified the original conversion as triggering the issues there.

Fixes: 7a8b64d17e35 ("of/address: use range parser for of_dma_get_range")
Signed-off-by: Mark Brown <broonie@...nel.org>
Cc: Luca Di Stefano <luca.distefano@...aro.org>
Cc: 993612@...s.debian.org
Cc: stable@...nel.org
---
 drivers/of/address.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index c34ac33b7338..21342223b8e5 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -975,10 +975,12 @@ int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
 	}

 	/*
-	 * Record all info in the generic DMA ranges array for struct device.
+	 * Record all info in the generic DMA ranges array for struct device,
+	 * returning an error if we don't find any parsable ranges.
 	 */
 	*map = r;
 	of_dma_range_parser_init(&parser, node);
+	ret = -EINVAL;
 	for_each_of_range(&parser, &range) {
 		pr_debug("dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
 			 range.bus_addr, range.cpu_addr, range.size);
@@ -992,6 +994,7 @@ int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
 		r->size = range.size;
 		r->offset = range.cpu_addr - range.bus_addr;
 		r++;
+		ret = 0;
 	}
 out:
 	of_node_put(node);

---
base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
change-id: 20230126-synquacer-boot-243bd1b87f64

Best regards,
-- 
Mark Brown <broonie@...nel.org>