netdev - [PATCH 4/6] dma-direct: warn when coherent allocations aren't supported

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Message-Id: <20231009074121.219686-5-hch@lst.de>
Date: Mon,  9 Oct 2023 09:41:19 +0200
From: Christoph Hellwig <hch@....de>
To: iommu@...ts.linux.dev
Cc: Robin Murphy <robin.murphy@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Wei Fang <wei.fang@....com>,
	Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>,
	NXP Linux Team <linux-imx@....com>,
	linux-m68k@...ts.linux-m68k.org,
	netdev@...r.kernel.org,
	Jim Quinlan <james.quinlan@...adcom.com>
Subject: [PATCH 4/6] dma-direct: warn when coherent allocations aren't supported

Log a warning once when dma_alloc_coherent fails because the platform
does not support coherent allocations at all.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 kernel/dma/direct.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 1327d04fa32a25..fddfea3b2fe173 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -240,8 +240,10 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 		 */
 		set_uncached = IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED);
 		remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
-		if (!set_uncached && !remap)
+		if (!set_uncached && !remap) {
+			pr_warn_once("coherent DMA allocations not supported on this platform.\n");
 			return NULL;
+		}
 	}
 
 	/*
-- 
2.39.2