FAILED: patch "[PATCH] swiotlb: fix unexpected swiotlb_alloc_coherent failures" failed to apply to 4.16-stable tree

The patch below does not apply to the 4.16-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Takashi Iwai <[email protected]>
Date: Tue, 10 Apr 2018 19:05:13 +0200
Subject: [PATCH] swiotlb: fix unexpected swiotlb_alloc_coherent failures

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

index 47aeb04c1997..de7cc540450f 100644
@@ -719,7 +719,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		goto out_warn;
 
 	*dma_handle = __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);