Difference dma_alloc_coherent() in x86_32 and x86_64

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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, &region_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
--
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs



[Index of Archives]     [Audio]     [Hams]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Fedora Users]

  Powered by Linux