How does Cortex-m4 interacts with other master devices such as DMA while m4 core does not have Hbusreq and Hgrant ports? m4 core does not have interfaces to arbiter.
Chip designers can use components like AHB bus matrix or AHB master multiplexer to support multiple bus masters.
AHB bus matrix:
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0479d/BABDDFFJ.html
AHB master multiplexer:
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0479d/BABJEICJ.html
The arbitration is handled inside these components.
regards,
joseph