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 stable@vger.kernel.org.

thanks,

greg k-h

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

From 9e7f06c8beee304ee21b791653fefcd713f48b9a Mon Sep 17 00:00:00 2001

From: Takashi Iwai tiwai@suse.de 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 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

diff --git a/lib/swiotlb.c b/lib/swiotlb.c index 47aeb04c1997..de7cc540450f 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -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);