Posted on January 29, 2008 at 13:41Hi all,
I'm trying FDMA to do a memory-to-memory copy function instead of using copy_to_user(). I followed the stlinux example below (http://www.stlinux.com/docs/manual/distribution/fdma_sh_exmpl1.php)
unsigned long flags=
STM_DMA_SETUP_CONTEXT_TASK
| DIM_1_x_1
| MODE_SH_COMPATIBILITY;
unsigned long xfer_bytes =4096;
void* src_buff = kmalloc(xfer_bytes,GFP_KERNEL);
void * dst_buff = kmalloc(xfer_bytes,GFP_KERNEL);
int ch_num = request_dma(0,__FUNCTION__);
if(!ch_num ==0)
return -ENODEV;
if(src_buff){
memset(src_buff,0x4,xfer_bytes);
dma_cache_wback(&src_buff[0],sizeof(u32)*xfer_bytes);
dma_cache_wback(&dst_buff[0],sizeof(u32)*xfer_bytes);
dma_configure_channel(ch_num,flags);
dma_xfer(ch_num,
virt_to_phys((void*)src_buff),
virt_to_phys((void*)dst_buff)
,xfer_bytes,
MODE_SH_COMPATIBILITY);
dma_wait_for_completion(ch_num);
if(memcmp((void*)src_buff,(void*)dst_buff,xfer_bytes)!=0){
dump_srcbuff(src_buff,xfer_bytes);
dump_dstbuff(dst_buff,xfer_bytes);
panic('' memory does not compare\n'');
}
printk(''woken up from DMA - TEST OK\n'');
kfree((void*)src_buff);
kfree((void*)dst_buff);
free_dma(ch_num);
return 0;
}
return -ENOMEM;
then got an error that looks like this:
..
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pc = 86cd56aa
*pde = 00000000
Oops: 0001 [#1]
Pid : 818, Comm: udhcpc
PC is at create_llu_list+0x86/0x8c
PC : 86cd56aa SP : 8f633d38 SR : 40008001 TEA : c0103a64 Not tainted
R0 : 00000000 R1 : 00000000 R2 : 8f633d80 R3 : 00000001
R4 : 8f633d80 R5 : 00000000 R6 : 00000000 R7 : 00000000
R8 : 00000001 R9 : 8f633d40 R10 : 00000030 R11 : 86d6616c
R12 : 0f516ae0 R13 : 86d6616c R14 : 8fbc6000
MACH: 00000000 MACL: 00000000 GBR : 295737e8 PR : 86cd696c
my box use STB710x, SH architecture and stlinux-2.6.17.14. Could someone tell me a clue to my problem, please?
If I change the flag to use ''MODE_FREERUNNING'', then I got another error: CH_0 invalid descriptor
How should I configure the flags then?
Thank you very much and sorry if this is not the right place to ask this kind of problems!
/ha
