linux-kernel - [PATCH 2/2] mtd: nand: omap2: Fix high memory dma prefetch transfer

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Date:	Fri, 15 Apr 2016 15:28:59 -0500
From:	Franklin S Cooper Jr <fcooper@...com>
To:	boris.brezillon@...e-electrons.com, dwmw2@...radead.org,
	computersforpeace@...il.com, tony@...mide.com, rogerq@...com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Cc:	"Cooper Jr., Franklin" <fcooper@...com>
Subject: [PATCH 2/2] mtd: nand: omap2: Fix high memory dma prefetch transfer

From: "Cooper Jr., Franklin" <fcooper@...com>

Based on DMA documentation and testing using high memory buffer when doing
dma transfers can lead to various issues including kernel panics.

To workaround this simply use cpu copy.

Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
---
 drivers/mtd/nand/omap2.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 762e0ed..8d0ae3a 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -467,17 +467,8 @@ static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
 	int ret;
 	u32 val;
 
-	if (addr >= high_memory) {
-		struct page *p1;
-
-		if (((size_t)addr & PAGE_MASK) !=
-			((size_t)(addr + len - 1) & PAGE_MASK))
-			goto out_copy;
-		p1 = vmalloc_to_page(addr);
-		if (!p1)
-			goto out_copy;
-		addr = page_address(p1) + ((size_t)addr & ~PAGE_MASK);
-	}
+	if (!virt_addr_valid(addr))
+		goto out_copy;
 
 	sg_init_one(&sg, addr, len);
 	n = dma_map_sg(info->dma->device->dev, &sg, 1, dir);
-- 
2.7.0