wiki:Component/VciLocks

Version 14 (modified by alinevieiramello@…, 14 years ago) (diff)

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SocLib Components General Index

VciLocks

1) Functional Description

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.

2) Component definition & usage

source:trunk/soclib/soclib/module/internal_component/vci_locks/caba/metadata/vci_locks.sd

See SoclibCc/VciParameters

Uses( 'vci_locks', **vci_parameters )

3) CABA Implementation

CABA sources

CABA Constructor parameters

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

CABA Ports

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

4) TLM-T implementation

TLM-T sources

TLM-T Constructor parameters

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

TLM-T Ports

  • soclib::tlmt::VciTarget<vci_param> p_vci : The VCI port

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