From: tochansky@tochlab.net
To: linux-newbie@vger.kernel.org
Subject: Difference dma_alloc_coherent() in x86_32 and x86_64
Date: Tue, 16 Feb 2016 14:22:50 +0300 [thread overview]
Message-ID: <f114e083ea781d6cd7836b9e6a684241@tochlab.net> (raw)
Hello!
I have a driver for PCI device which uses CMA framework for allocating
big coherent blocks of memory for DMA.
Allocation looks like:
typedef struct {
struct list_head list;
uint32_t size8;
void *kaddr;
dma_addr_t paddr;
} dma_region_t;
LIST_HEAD(region_list);
......
void* AllocDMA( size_t size )
{
dma_region_t *new_region;
new_region = kmalloc(sizeof(dma_region_t), GFP_KERNEL);
new_region->size8 = size;
new_region->kaddr = dma_alloc_coherent( NULL, size,
&new_region->paddr, GFP_KERNEL | GFP_DMA32 );
list_add(&new_region->list, ®ion_list);
printk("pcidev: cma_alloc paddr %pad kaddr %p size %d\n",
&new_region->paddr, new_region->kaddr, new_region->size8);
return new_region->kaddr;
}
It works fine on kernel 3.18.26 in 32bit mode.
When I reconfigure same kernel to run in 64bit mode(enabling in
'menuconfig' option '64-bit kernel') and trying to use this driver with
it
allocation failed with message in dmesg:
...
[ 1393.835535] fallback device: swiotlb buffer is full (sz: 8388608
bytes)
[ 1393.835579] pcidev: cma_alloc paddr 0xffff880234861220 kaddr
(null) size 8388608
...
My kernel command line is: swiotlb=16384 iommu=soft cma=256M
Anyone can explain this strange behavior?
--
D
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reply other threads:[~2016-02-16 11:22 UTC|newest]
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