Microblaze, DMA and cache: Lack of sync functions?

Microblaze, DMA and cache: Lack of sync functions?

[Eli Billauer]

Hello,


Before I make a needless hack, please correct me if I'm wrong: in 
arch/microblaze/kernel/dma.c, the sync_single_for_cpu, 
sync_single_for_device and friends are not set in the dma_direct_ops 
structure (and not implemented), so calls from drivers to the 
corresponding functions will do nothing. Since the Microblaze cache 
doesn't update automatically on DMA operations, this looks like a bug to 
me: The driver thinks the cache has been flushed or updated, but it 
actually hasn't.


Map and unmap methods are indeed implemented and registered, and they 
both call an internal function to sync the cache. So why are there no 
sync functions?

To hack or not to hack?

   Eli

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Web: http://www.billauer.co.il

Re: Microblaze, DMA and cache: Lack of sync functions?

[Michal Simek]

Eli Billauer wrote:
> Hello,
> 
> 
> Before I make a needless hack, please correct me if I'm wrong: in 
> arch/microblaze/kernel/dma.c, the sync_single_for_cpu, 
> sync_single_for_device and friends are not set in the dma_direct_ops 
> structure (and not implemented), so calls from drivers to the 
> corresponding functions will do nothing. Since the Microblaze cache 
> doesn't update automatically on DMA operations, this looks like a bug to 
> me: The driver thinks the cache has been flushed or updated, but it 
> actually hasn't.
> 
> 
> Map and unmap methods are indeed implemented and registered, and they 
> both call an internal function to sync the cache. So why are there no 
> sync functions?
> 

It is not the bug just unimplemented feature and I haven't had any problem
that these functions are not implemented.
Implementation should be pretty straight forward. Patches welcomed.

Thanks,
Michal




-- 
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663