linux-kernel - [PATCH v2 1/2] drivers: dma-coherent: Fix DMA coherent size for less than page

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Message-ID: <1475049117-12201-2-git-send-email-Mark_Craske@mentor.com>
Date:   Wed, 28 Sep 2016 08:51:56 +0100
From:   Mark Craske <Mark_Craske@...tor.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     <linux-kernel@...r.kernel.org>,
        "George G. Davis" <George_Davis@...tor.com>,
        Jiada Wang <Jiada_Wang@...tor.com>
Subject: [PATCH v2 1/2] drivers: dma-coherent: Fix DMA coherent size for less than page

From: "George G. Davis" <george_davis@...tor.com>

We fix a bug in dma_mmap_from_coherent() that appears when we map non page
aligned DMA memory. It cuts off the non aligned part (this is different to
dma_alloc_coherent() that always rounds up to full pages). So for mappings
of less than a page we get -ENXIO as dma_mmap_from_coherent() assumes we
want to map zero pages.

Signed-off-by: George G. Davis <george_davis@...tor.com>
Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
Signed-off-by: Mark Craske <Mark_Craske@...tor.com>
---
 drivers/base/dma-coherent.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index db122a0..2789f7a 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -262,7 +262,7 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
 		unsigned long off = vma->vm_pgoff;
 		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		int user_count = vma_pages(vma);
-		int count = size >> PAGE_SHIFT;
+		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
 		*ret = -ENXIO;
 		if (off < count && user_count <= count - off) {
-- 
1.7.9.5