Badness in dma_alloc_init

Badness in dma_alloc_init

[Kalle Pokki]

Hi all,

I'm having some trouble with the DMA allocation using Linux 2.6.14-rc2 + 
some platform modifications. Namely, the dma_alloc_coherent() function 
returns bogus virtual addresses causing machine check exceptions. At 
boot, the kernel complains there is something wrong, but I cannot figure 
out how to fix it. CONFIG_CONSISTENT_START is at its default value, 
0xff100000. Any hints where to look further?

Oh, this is a custom 8xx board. Has the support for DMA in 8xx been 
unstable at the time of pre-2.6.14?

Linux version 2.6.14-rc2 (kp@host32.eke.fi) (gcc version 4.0.0 (DENX 
ELDK 4.0 4.
0.0)) #1 Mon Jan 9 12:53:41 EET 2006
Built 1 zonelists
Kernel command line: root=/dev/mtdblock1 ro console=ttyCPM0,115200
PID hash table entries: 256 (order: 8, 4096 bytes)
Decrementer Frequency = 247500000/60
Console: colour dummy device 80x25
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
Memory: 30268k available (1608k kernel code, 376k data, 100k init, 0k 
highmem)
Mount-cache hash table entries: 512
Badness in dma_alloc_init at arch/ppc/kernel/dma-mapping.c:348
Call trace: [c0003670]  [c0003f24]  [c0003320]  [c01e2ad0]  [c000228c]  
[c000551
c]

... followed by otherwise good startup.

Re: Badness in dma_alloc_init

[Aristeu Sergio Rozanski Filho]

Hi!
> I'm having some trouble with the DMA allocation using Linux 2.6.14-rc2 + 
> some platform modifications. Namely, the dma_alloc_coherent() function 
> returns bogus virtual addresses causing machine check exceptions. At 
> boot, the kernel complains there is something wrong, but I cannot figure 
> out how to fix it. CONFIG_CONSISTENT_START is at its default value, 
> 0xff100000. Any hints where to look further?
> 
> Oh, this is a custom 8xx board. Has the support for DMA in 8xx been 
> unstable at the time of pre-2.6.14?
probably your IMAP_ADDR is at 0xff000000, isn't it? if it is, please adjust
CONFIG_CONSISTENT_START to an address like 0xe0000000.

-- 
Aristeu

Re: Badness in dma_alloc_init

[Kalle Pokki]

Aristeu Sergio Rozanski Filho wrote:

>Hi!
>  
>
>>I'm having some trouble with the DMA allocation using Linux 2.6.14-rc2 + 
>>some platform modifications. Namely, the dma_alloc_coherent() function 
>>returns bogus virtual addresses causing machine check exceptions. At 
>>boot, the kernel complains there is something wrong, but I cannot figure 
>>out how to fix it. CONFIG_CONSISTENT_START is at its default value, 
>>0xff100000. Any hints where to look further?
>>
>>Oh, this is a custom 8xx board. Has the support for DMA in 8xx been 
>>unstable at the time of pre-2.6.14?
>>    
>>
>probably your IMAP_ADDR is at 0xff000000, isn't it? if it is, please adjust
>CONFIG_CONSISTENT_START to an address like 0xe0000000.
>
>  
>
True, my IMAP_ADDR is at 0xff000000. But IMAP_SIZE is just 64 KB, so 
there should be no overlap, right? Or is the IMAP memory area mapped 
with an 8-MB TLB entry or something like that?

No badness in dma-mapping.c anymore with CONFIG_CONSISTENT_START being 
0xe0000000, however. Thanks.