linux-kernel - [PATCH] dma-coherent: fix rmem_dma_device

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Date:   Fri, 15 Sep 2017 17:08:16 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Roy Pledge <roy.pledge@....com>, Arnd Bergmann <arnd@...db.de>,
        Robin Murphy <robin.murphy@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        "George G. Davis" <george_davis@...tor.com>,
        Mark Craske <Mark_Craske@...tor.com>,
        Bastian Hecht <bhecht@...adit-jv.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] dma-coherent: fix rmem_dma_device_init regression

My recent bug fix introduced another bug, which caused rmem_dma_device_init
to always fail, as rmem->priv is never set to anything.

This restores the previous behavior, calling dma_init_coherent_memory()
whenever ->priv is NULL.

Fixes: d35b0996fef3 ("dma-coherent: fix dma_declare_coherent_memory() logic error")
Reported-by: Roy Pledge <roy.pledge@....com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Roy, can you test this new fix?
---
 drivers/base/dma-coherent.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index a39b2166b145..744f64f43454 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -348,16 +348,15 @@ static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 	struct dma_coherent_mem *mem = rmem->priv;
 	int ret;
 
-	if (!mem)
-		return -ENODEV;
-
-	ret = dma_init_coherent_memory(rmem->base, rmem->base, rmem->size,
-				       DMA_MEMORY_EXCLUSIVE, &mem);
-
-	if (ret) {
-		pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
-			&rmem->base, (unsigned long)rmem->size / SZ_1M);
-		return ret;
+	if (!mem) {
+		ret = dma_init_coherent_memory(rmem->base, rmem->base,
+					       rmem->size,
+					       DMA_MEMORY_EXCLUSIVE, &mem);
+		if (ret) {
+			pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %ld MiB\n",
+				&rmem->base, (unsigned long)rmem->size / SZ_1M);
+			return ret;
+		}
 	}
 	mem->use_dev_dma_pfn_offset = true;
 	rmem->priv = mem;
-- 
2.9.0