wiki:Component/VciMultiAhci

Version 2 (modified by alain, 10 years ago) (diff)

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SocLib Components General Index

VciMultiAhci

1) Functional Description

This component emulates a multi-channels disk controller with VCI interface. Each channel[k] can access a different physical disk, modeled as a different file[k] belonging to the host system, and containing a complete disk image. Each channel[k] can perform data transfers between file[k] and a buffer in the physical memory of the virtual system. he number of supported channels, the file name(s), the VCI burst size, and the block size are hardware parameters,defined as constructors parameters. The number of channels cannot be larger than 8. The burst size must be a power of 2 between 8 and 64 bytes. The block size must be a power of 2 between 128 and 4096 bytes.

According to the AHCI specification, each channel[k] controller uses a private Command List that is handled as a software FIFO. For each channel[k], the Command List can register up to 32 read or write commands, that are handled in pseudo-parallelism by the channel controller. This VCI component has a DMA capability, and use it to access both the Command List and to transfer the data to or from memory.

On the VCI side, it supports both 32 bits and 64 bits data words, and up to 64 bits address width.

For each channel, a single IRQ[k] can be (optionally) asserted as soon as at list one command in the Command List is completed. WARNING: the IRQ[k] is associated to a specific channel, but not to a specific command.

This hardware component checks for segmentation violation, and can be used as a default target.

2) Command List

For each channel, the Vci Multi Ahci driver must use two arrays to register commands: The Command Descriptor array (32 entries) define the Command List (software FIFO). Each Command Descriptor occupies 16 bytes, with the following format: 

typedef struct hba_cmd_desc_s  // size = 16 bytes
{
    unsigned char       flag[2];        // only one bit used : WRITE when bit 6 of flag[0] is set 
    unsigned char       prdtl[2];	// Number of buffers (no more than 16535)
    unsigned int        prdbc;		// Number of bytes actually transfered
    unsigned int        ctba;		// Command Table base address 32 LSB bits
    unsigned int        ctbau;		// Command Table base address 32 MSB bits
} hba_cmd_desc_t;

3) Command Table

2) Addressable registers

Each channel[k] contains six 32 bits read/write registers:

  • HBA_PXCLB

32 LSB bits of the Command List array physical address.

  • HBA_PXCLBU

32 MSB bits of the Command List array physical address. *

  • HBA_PXIS

Channel status, used for error reporting.

  • HBA_PXIE

Intcommanderrupt enable.

  • HBA_PXCMD

Boolean : running when non zero

  • HBA_PXCI

Bit-vector, one bit per command in the Command List. These bits are handled as 32 set/reset flip-flops: set by software when a command ha been posted in Command List / reset by hardware when the command is completed.

  • BLOCK_DEVICE_OP (write only)

Type of operation, writing here initiates the operation.This register goes back to BLOCK_DEVICE_NOOP when operation is finished. The following operations codes are defined:

BLOCK_DEVICE_NOOP No operation
BLOCK_DEVICE_READ Transfer from block device to memory
BLOCK_DEVICE_WRITE Transfer from memory to block device
  • BLOCK_DEVICE_STATUS (read only)

State of the transfer. Reading this register while not busy resets its value to IDLE, and acknowledge the IRQ. Value may be one of :

BLOCK_DEVICE_IDLE
BLOCK_DEVICE_BUSY
BLOCK_DEVICE_READ_SUCCESS
BLOCK_DEVICE_WRITE_SUCCESS
BLOCK_DEVICE_READ_ERROR
BLOCK_DEVICE_WRITE_ERROR
  • BLOCK_DEVICE_IRQ_ENABLE (read/write)

Boolean enabling the IRQ line

  • BLOCK_DEVICE_SIZE (read only)

Number of blocks addressable in the block device

  • BLOCK_DEVICE_BLOCK_SIZE (read only)

Block size (in bytes)

For extensibility issues, you should access this component using globally-defined offsets. You should include file soclib/block_device.h from your software, it defines BLOCK_DEVICE_COUNT, BLOCK_DEVICE_READ, ...

Sample code: Please see reference implementation in source:trunk/soclib/soclib/platform/topcells/caba-vgmn-block_device-mips32el

(add -I/path/to/soclib/include to your compilation command-line)

2) Component definition & usage

source:trunk/soclib/soclib/module/connectivity_component/vci_block_device/caba/metadata/vci_block_device.sd​

See SoclibCc/VciParameters 

Uses( 'vci_block_device', **vci_parameters )

3) CABA Implementation

CABA sources

CABA Constructor parameters

VciBlockDevice(
     sc_module_name name,   //  Component Name
     const soclib::common::MappingTable &mt, // MappingTable
     const soclib::common::IntTab &srcid,    // Initiator index
     const soclib::common::IntTab &tgtid,    // Target index
     const std::string &filename, // mapped file, may be a host block device
     const uint32_t block_size = 512, // block size in bytes
     const uint32_t latency = 0);  // initial access time (number of cycles)

CABA Ports

  • p_resetn : Global system reset
  • p_clk : Global system clock
  • p_vci_target : The VCI target port
  • p_vci_initiator : The VCI initiator port
  • p_irq : Interrupt port

4) TLM-DT Implementation

TLM-DT sources

TLM-DT Constructor parameters

VciBlockDevice(
     sc_module_name name,   //  Component Name
     const soclib::common::MappingTable &mt, // MappingTable
     const soclib::common::IntTab &srcid,    // Initiator index
     const soclib::common::IntTab &tgtid,    // Target index
     const std::string &filename, // mapped file, may be a host block device
     const uint32_t block_size = 512, // block size in bytes
     const uint32_t latency = 0);  // initial access time (number of cycles)

TLM-DT Ports

  • p_vci_target : The VCI target port
  • p_vci_initiator : The VCI initiator port
  • p_irq : Interrupt port