Cache routines working with a processor set?

Sebastian Huber sebastian.huber at
Fri Dec 21 14:06:19 UTC 2018

Hello Daniel,

On 21/12/2018 14:55, Daniel Hellstrom wrote:
> I missed to respond to this email.. It is not currently used by our 
> drivers currently, I think the original use case here is when 
> L3/L2/L1-cache is not updated after DMA. For example, the GR740 can be 
> configured to make DMA directly to SDRAM memory, "behind" the 
> L2-cache. In this mode the system is not coherent. To avoid the L2 
> cache containing incorrect data, one approach is to use a "DMA address 
> region" and configure a L2-cache MTR regions. However, the L1-cache 
> would still not be updated since it L1 D-cache is not snooping the 
> memory bus but only the CPU bus which the DMA master is not writing to 
> in this configuration. Using the MMU and marking pages non-cacheable 
> could resolve this to a cost. Another approach would be to flush those 
> lines or the whole D-cache instead of using the MMU. At that time, it 
> was under consideration to add line/page flushing to the GR740 L1-cache.

this sounds like a very specialized use case. I don't think we should 
provide an architecture-independent API for this. If you really need 
this for a highly optimized driver on the GR740, you can use a special 
purpose function.

> For the I-cache we need to flush when modifying instructions, like the 
> trap vector. But this patch seems to only involve d-cache. 

The instruction cache software broadcast is still supported.

Sebastian Huber, embedded brains GmbH

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