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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Takashi Iwai <tiwai@suse.de>,
        Christoph Hellwig <hch@lst.de>, Jean Delvare <jdelvare@suse.de>
Subject: [PATCH 4.16 058/196] swiotlb: fix unexpected swiotlb_alloc_coherent failures
Date:   Sun, 22 Apr 2018 15:51:18 +0200
Message-Id: <20180422135107.210672134@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 9e7f06c8beee304ee21b791653fefcd713f48b9a upstream.

The code refactoring by commit 0176adb00406 ("swiotlb: refactor coherent
buffer allocation") made swiotlb_alloc_buffer almost always failing due
to a thinko: namely, the function evaluates the dma_coherent_ok call
incorrectly and dealing as if it's invalid. This ends up with weird
errors like iwlwifi probe failure or amdgpu screen flickering.

This patch corrects the logic error.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 lib/swiotlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -732,7 +732,7 @@ swiotlb_alloc_buffer(struct device *dev,
 		goto out_warn;
 
 	*dma_handle = swiotlb_phys_to_dma(dev, phys_addr);
-	if (dma_coherent_ok(dev, *dma_handle, size))
+	if (!dma_coherent_ok(dev, *dma_handle, size))
 		goto out_unmap;
 
 	memset(phys_to_virt(phys_addr), 0, size);