VciLocks Functional Description

SocLib Components General Index

This VCI target is a locks controller : In VCI-based systems, it is not anymore possible to "lock the bus" to implement the atomic test & set instructions used for software synchronisation. Therefore, this memory mapped hardware peripheral implements a set of binary locks:

• Each binary lock is a single flip-flop, but corresponds to 4 bytes in the address space. The segment allocated to this component must be aligned on a 4 bytes boundary. The number of available locks is defined by segment_size / 4.
• Any read request is interpreted as a test & set operation : the value stored in the addressed flip-flop is returned, and the addressed flip-flop is set to 1.
• All write request are interpreted as reset : the addressed flip-flop is reset to 0.

This way, a spin lock is implemented as a simple loop waiting to read 0, and the lock release is a simple write operation. This components checks addresses for segmentation violation, and can be used as default target.

VciLocks CABA Implementation

The caba implementation is in

• source:trunk/soclib/systemc/include/caba/target/vci_locks.h
• source:trunk/soclib/systemc/src/caba/target/vci_locks.cc

Template parameters:

• The VCI parameters

Constructor parameters

VciLocks(
     sc_module_name name,   // Instance name
     const soclib::common::IntTab &index,   //  Target index
     const soclib::common::MappingTable &mt);   // Mapping Table

Ports

• sc_in<bool> p_resetn : Global system reset
• sc_in<bool> p_clk : Global system clock
• soclib::common::VciiTarget<vci_param> p_vci : The VCI port