linux-kernel - [PATCH] drivers: dma-coherent: use ioremap_wc() for DMA_MEMORY

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Message-Id: <1448029226-4914-1-git-send-email-brian.starkey@arm.com>
Date:	Fri, 20 Nov 2015 14:20:26 +0000
From:	Brian Starkey <brian.starkey@....com>
To:	gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] drivers: dma-coherent: use ioremap_wc() for DMA_MEMORY_MAP

When the DMA_MEMORY_MAP flag is used, memory which can be accessed
directly should be returned, so use ioremap_wc() instead of ioremap().
Also, ensure that the correct memset operation is used in
dma_alloc_from_coherent() with respect to the region's flags.

This fixes the below alignment fault on arm64, caused by invalid use
of memset() on Device memory.

   Unhandled fault: alignment fault (0x96000061) at 0xffffff8000380000
   Internal error: : 96000061 [#1] PREEMPT SMP
   Modules linked in: hdlcd(+) clk_scpi
   CPU: 4 PID: 1355 Comm: systemd-udevd Not tainted 4.4.0-rc1+ #5
   Hardware name: ARM Juno development board (r0) (DT)
   task: ffffffc9763eee00 ti: ffffffc9758c4000 task.ti: ffffffc9758c4000
   PC is at __efistub_memset+0x1ac/0x200
   LR is at dma_alloc_from_coherent+0xb0/0x120
   pc : [<ffffffc00030ff2c>] lr : [<ffffffc00042a918>] pstate: 400001c5
   sp : ffffffc9758c79a0
   x29: ffffffc9758c79a0 x28: ffffffc000635cd0
   x27: 0000000000000124 x26: ffffffc000119ef4
   x25: 0000000000010000 x24: 0000000000000140
   x23: ffffffc07e9ac3a8 x22: ffffffc9758c7a58
   x21: ffffffc9758c7a68 x20: 0000000000000004
   x19: ffffffc07e9ac380 x18: 0000000000000001
   x17: 0000007fae1bbba8 x16: ffffffc0001b2d1c
   x15: ffffffffffffffff x14: 0ffffffffffffffe
   x13: 0000000000000010 x12: ffffff800837ffff
   x11: ffffff800837ffff x10: 0000000040000000
   x9 : 0000000000000000 x8 : ffffff8000380000
   x7 : 0000000000000000 x6 : 000000000000003f
   x5 : 0000000000000040 x4 : 0000000000000000
   x3 : 0000000000000004 x2 : 000000000000ffc0
   x1 : 0000000000000000 x0 : ffffff8000380000

Signed-off-by: Brian Starkey <brian.starkey@....com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
---
 drivers/base/dma-coherent.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 55b8398..45358d0 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -31,7 +31,10 @@ static int dma_init_coherent_memory(phys_addr_t phys_addr, dma_addr_t device_add
 	if (!size)
 		goto out;
 
-	mem_base = ioremap(phys_addr, size);
+	if (flags & DMA_MEMORY_MAP)
+		mem_base = ioremap_wc(phys_addr, size);
+	else
+		mem_base = ioremap(phys_addr, size);
 	if (!mem_base)
 		goto out;
 
@@ -181,7 +184,10 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
 	 */
 	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
 	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
-	memset(*ret, 0, size);
+	if (mem->flags & DMA_MEMORY_MAP)
+		memset(*ret, 0, size);
+	else
+		memset_io(*ret, 0, size);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 
 	return 1;
-- 
1.7.9.5

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