linux-kernel - [RFC PATCH v2] arm DMA: Fix allocation from CMA for coherent DMA

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Date:	Wed,  3 Jun 2015 19:15:45 +0200
From:	Lorenzo Nava <lorenx4@...il.com>
To:	arnd@...db.de
Cc:	linux@....linux.org.uk, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, catalin.marinas@....com,
	Lorenzo Nava <lorenx4@...il.com>
Subject: [RFC PATCH v2] arm DMA: Fix allocation from CMA for coherent DMA

This patch allows the use of CMA for DMA coherent memory allocation.
At the moment if the input parameter "is_coherent" is set to true 
the allocation is not made using the CMA, which I think is not the 
desired behaviour.

Signed-off-by: Lorenzo Nava <lorenx4@...xxxxx>
---
Changes in v2:
 correct __arm_dma_free() according to __dma_alloc() allocation
---
 arch/arm/mm/dma-mapping.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 7e7583d..15643b9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -645,9 +645,9 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	size = PAGE_ALIGN(size);
 	want_vaddr = !dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs);
 
-	if (is_coherent || nommu())
+	if (nommu())
 		addr = __alloc_simple_buffer(dev, size, gfp, &page);
-	else if (!(gfp & __GFP_WAIT))
+	else if (!is_coherent && !(gfp & __GFP_WAIT))
 		addr = __alloc_from_pool(size, &page);
 	else if (!dev_get_cma_area(dev))
 		addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller, want_vaddr);
@@ -735,7 +735,7 @@ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
 
 	size = PAGE_ALIGN(size);
 
-	if (is_coherent || nommu()) {
+	if (nommu()) {
 		__dma_free_buffer(page, size);
 	} else if (__free_from_pool(cpu_addr, size)) {
 		return;
-- 
1.7.10.4

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