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iMX6 EIM transfer speed with using NEON vld/vst instructions

Question asked by torus1000 on Apr 7, 2014
Latest reply on Mar 27, 2015 by Sumeet Dube

I tried to estimate EIM transfer rate then measured burst length and CS interval of 32b EIM memory when following NEON code was running.
The results are:
   VLDM(32b EIMmem read):  16burst x2,  700ns from burst end to next burst
   VSTM(32b EIMmem write):  2burst x16,  455ns from burst end to next burst


Could someone explain why burst length and above period are different?
Is there any special EIM or NIC-301 setting need for such NEON codes?


---------- my code -------------


          PLD   [r1,     #0x80]

          VLDM  r1!,     {d0-d15}   #EIMmem read 128byte

          PLDW  [r0,     #0x80]

          VSTM  r0!,     {d0-d15}  #EIMmem write  128byte

          SUBS  r2,  r2, #0x80

          BGT NEONCopyPLD