0x800000 is the max amount I've been able to allocate.  I think it has 
something to do with max size allowed by dma_alloc_coherent with the 
GFP_KERNEL flag.  The max with the beaglebone white (256mb ram instead of 
512mb) was 0x400000.  So far I haven't been able to turn up where these 
limits may be coming from though.. someone suggested it may be tunable with 
a kernel parameter.



On Thursday, November 7, 2013 12:32:11 AM UTC-5, [email protected] wrote:
>
> I'm running Angstrom (Linux 3.8.13, September 12, 2013) on a BeagleBone 
> Black and I've tried configuring uio_pruss to allocate a large amount of 
> external memory, but I have found that sizes greater than 8MB don't work 
> and lead to uio_pruss failure.
>
> The command I have been trying is:
>
> /sbin/modprobe uio_pruss extram_pool_sz=0x800001
>
>
> ... and the error message I receive is:
>
> pruss_uio 4a300000.pruss: Could not allocate external memory
>
>
> I would like to allocate more than 8MB of external memory for PRU access. 
>  Is it possible to allocate more than 8MB?  If so, what can I do to make it 
> work?
>

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