On Tue, 8 Jan 2013 23:51:59 +0800
Jeff Chua <jeff.chua.li...@gmail.com> wrote:
> I'm trying to understand how this oops in the diva driver and it's just a
> simple dma_alloc_coherent() followed by dma_free_coherent(), but it oops.
> Why?
Hmm...from a quick look...
> static u32 *clock_data_addr;
> static dma_addr_t clock_data_bus_addr;
>
> if((clock_data_addr = dma_alloc_coherent(NULL, PAGE_SIZE,
> &clock_data_bus_addr, GFP_KERNEL)) != 0) {
> printk(KERN_INFO "dma_alloc_coherent ok\n");
> memset (clock_data_addr, 0x00, PAGE_SIZE);
> } else
> printk(KERN_INFO "dma_alloc_coherent bad!!!\n");
> if(clock_data_addr) {
> printk(KERN_INFO "dma_free_coherent!!!\n");
> dma_free_coherent(NULL, PAGE_SIZE, clock_data_addr,
> clock_data_bus_addr);
> clock_data_addr = NULL;
> }
Perhaps passing NULL as your device structure pointer might just have
something to do with a crash due to a null pointer dereference? If you're
doing DMA, you should have a device. Try passing it and you might just
find that things work better.
(Incidentally, this:
> IP: [<ffffffff813ec01c>] iommu_no_mapping+0xc/0xee
is a fairly good clue as well - it's trying to dereference the device
structure pointer).
jon
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