> > *When I run experiments I see that the physical addresses are contiguous, > but are they guaranteed to be? or has this just been "lucky"?* >
If memory serves, I think they have to be. But, if as you say you've tested and they've come up contiguous already, then I'm very sure this can not change. Not unless they memory is somehow freed using free(), and I do not think that is possible . . . On Fri, Feb 5, 2016 at 5:33 PM, Bill Gray <[email protected]> wrote: > Hi, > > I've got PRU0 of my BBB pulling in 12 Bytes of data from a ADC with a > sampling frequency of 31250hz. > > I want to stash all of this data in an array that lives in DDR memory. I > would like to make the array 0x4000 bytes (16kB) large. This would give me > 1365 12 byte records and about 43ms of data to play with. > > I'm currently using prussdrv_map_extmem() to hook me up with the DDR > memory. It provides me with a memory block that is 256kB, so I have plenty > of room. > > The question I have is... can I count on the physical address in this > 256kB block of memory to be contiguous? > > I'm pretty new to linux memory management, but I see that the "page size" > is only 4kB... so I imagine that the virtual memory system might chop my > 256kB block up into bits which might not necessarily have contiguous > addresses. > > If I can count on contiguous addresses, this radically simplifies the > memory access code in the PRU. If I can't... well, then I can't, and I've > got to figure something else out. > > When I run experiments I see that the physical addresses are contiguous, > but are they guaranteed to be? or has this just been "lucky"? > > Thanks, > > Bill > > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
