[U-Boot] [PATCH] Make kmalloc'ed memory really DMA-safe

[U-Boot] [PATCH] Make kmalloc'ed memory really DMA-safe

[Masahiro Yamada]

In Linux, the memory returned by kmalloc() is DMA-capable.
However, it is not true in U-Boot.

At a glance, kmalloc() in U-Boot returns address aligned with
ARCH_DMA_MINALIGN.  However, it never pads the allocated memory.
This half-way house is completely useless because calling kmalloc()
and malloc() in this order causes a cache sharing problem.

Change the implementation to call malloc_cache_aligned(), which
allocates really DMA-capable memory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 lib/linux_compat.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/linux_compat.c b/lib/linux_compat.c
index a936a7e..6373b44 100644
--- a/lib/linux_compat.c
+++ b/lib/linux_compat.c
@@ -1,5 +1,6 @@
 
 #include <common.h>
+#include <memalign.h>
 #include <linux/compat.h>
 
 struct p_current cur = {
@@ -18,7 +19,7 @@ void *kmalloc(size_t size, int flags)
 {
 	void *p;
 
-	p = memalign(ARCH_DMA_MINALIGN, size);
+	p = malloc_cache_aligned(size);
 	if (flags & __GFP_ZERO)
 		memset(p, 0, size);
 
@@ -37,5 +38,5 @@ struct kmem_cache *get_mem(int element_sz)
 
 void *kmem_cache_alloc(struct kmem_cache *obj, int flag)
 {
-	return memalign(ARCH_DMA_MINALIGN, obj->sz);
+	return malloc_cache_aligned(obj->sz);
 }
-- 
2.7.4

[U-Boot] Make kmalloc'ed memory really DMA-safe

[Tom Rini]

On Fri, Aug 24, 2018 at 07:30:15PM +0900, Masahiro Yamada wrote:

> In Linux, the memory returned by kmalloc() is DMA-capable.
> However, it is not true in U-Boot.
> 
> At a glance, kmalloc() in U-Boot returns address aligned with
> ARCH_DMA_MINALIGN.  However, it never pads the allocated memory.
> This half-way house is completely useless because calling kmalloc()
> and malloc() in this order causes a cache sharing problem.
> 
> Change the implementation to call malloc_cache_aligned(), which
> allocates really DMA-capable memory.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Applied to u-boot/master, thanks!

-- 
Tom
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