Hardware Platform Definition

ALMOS-MK has been designed to support clustered manycore architectures, using 32 bits cores (such as the MIPS32 based TSAR architecture), or 64 bits cores (such as the multi-cores INTEL/AMD architectures). Each cluster contains one or several cores, a variable number of addressable peripherals, and one physical memory bank. ALMOS-MK implements one kernel instance per cluster.

All relevant parameters describing the clustered multi-core architecture must be defined in the binary arch_info.bin file. This binary file is exploited by the ALMOS-MK boot loader to configure ALMOS-MK. It can be generated by a specific arch_info.py python scrip, for each target architecture.

1) Cluster and cores identification

1.1) Cluster identification

To identify a cluster in the clustered architecture, ALMOS-MK uses an unique cluster identifier cxy. ALMOS-MK does not make any assumption on the clusters topology, but makes the assumption that the cxy binary value can be directly concatened to the local physical address (address inside a cluster) to build a global physical address. Warning: The cluster identifier cxy is NOT a continuous index, and cannot be used to index a cluster array.

The size of the local physical address space (inside a cluster) is defined by a global parameter, that is the number of bits in a local physical address. The value of this parameter is 32 in architectures using 32 bits cores, but it can be larger in architectures using 64 bits cores. Any physical address is coded on 64 bits in ALMOS-MK.

Note : In architectures where the clusters are organized as a 2D mesh topology, is is generally possible to derive the [x,y] cluster coordinates from the cxy cluster identifier, and ALMOS-MK can use it to optimize placement and improve locality, but this optimisation is NOT mandatory, and ALMOS-MK supports architectures where the set of cluster is simply a linear vector of clusters.

1.2) Core identification

ALMOS-MK makes the assumption that each physical core contains an hardware addressable register defining an unique global identifier (called gid) with the only constraint that two different cores have two different gid.

To identify a specific core in the clustered architecture, ALMOS-MK does not use directly this physical gid, but uses a composite index [cxy,lid], where cxy is the cluster identifier, and lid is a local core index. This lid index is a continuous index in [0,N-1], where N can depend on the cluster, but cannot be larger than the global parameter CONFIG_MAX_CORE_PER_CLUSTER_NR.

The association of a composite index [cx,lid] to a global physical identifier gid, is defined in the arch_info.bin file.

2) Hardware architecture description

For ALMOS-MK, the target hardware architecture is described in the binary file arch_info.bin. This file is loaded from disk by the ALMOS-MK boot-loader.

2.1) General assumptions

• Each cluster contains a variable number of cores, a variable number of peripherals, and a physical memory bank.
• The number of clusters is variable (can be one).
• The cluster topology is variable (2D mesh or vector)
• The number of cores per cluster is variable (can be zero).
• The number of addressable peripherals per cluster is variable.
• The size of the physical memory bank per cluster is variable.
• Each cluster cover a fixed size segment in the physical address space.

2.2) the arch_info_t structure

The binary file arch_info.bin is a BLOB containing the binary form of the C arch_info_t structure. This structure has a three levels hierarchical organisation:

• the architecture contains a variable number of clusters.
• each cluster contains a variable number of cores and a variable number of addressable devices.
• some devices contains a variable number of input IRQs.

An adressable device can be a physical memory bank, or a peripheral containing addressable registers.

The arch_info.bin BLOB is organised as the concatenation of a fixed size header, and 4 variable size arrays of fixed size objects:

• archinfo_cluster_t cluster[]
• archinfo_core_t core[]
• archinfo_device_t device[]
• archinfo_irq_t irq[]

These five C structures are defined in the arch_info.h file. The access functions are defined in the arch_info.c file.

3) The python script =

This section defines the python constructs that can be used to generate the arch_info.bin binary file. These Python classes are defined in the genarch.py file.

The target hardware architecture must be defined in the arch.py file , you must use the following constructors:

3.1) architecture

The Archi( ) constructor build an archi object and defines the target architecture general parameters:

name	mapping name == architecture name
x_size	number of clusters in a row of the 2D mesh
y_size	number of clusters in a column of the 2D mesh
nprocs	max number of processors per cluster
x_width	number of bits to encode X coordinate in paddr
y_width	number of bits to encode Y coordinate in paddr
p_width	number of bits to encode local processor index
paddr_width	number of bits in physical address
coherence	Boolean true if hardware cache coherence
irq_per_proc	number of IRQ lines between XCU and one proc (GIET_VM use only one)
use_ramdisk	Boolean true if the architecture contains a RamDisk?
x_io	io_cluster X coordinate
y_io	io_cluster Y coordinate
peri_increment	virtual address increment for peripherals replicated in all clusters
reset_address	physical base address of the ROM containing the preloader code
ram_base	physical memory bank base address in cluster [0,0]
ram_size	physical memory bank size in one cluster (bytes)

3.2) Processor core

The archi.addProc( ) construct adds one processor core in a cluster. It associates a core composite index (cry, lid) to the core hardware index, and has has the following arguments:

cxy	cluster identifier
lid	local core index
gid	core hardware identifier

3.3) Physical memory bank

The archi.addRam( ) construct adds one physical memory segment in a cluster. It has the following arguments:

cxy	cluster identifier
base	local physical base address
size	segment size (bytes)

3.4) Peripheral

The archi.addPeriph( ) construct adds one peripheral in a cluster. ALMOS-MK supports multi-channels peripherals. This construct has the following arguments:

cxy	cluster identifier
base	local physical base address
size	segment size (bytes)
ptype	Peripheral type
subtype	Peripheral subtype
channels	number of channels for multi-channels peripherals
arg0	optionnal argument depending on peripheral type
arg1	optionnal argument depending on peripheral type
arg2	optionnal argument depending on peripheral type
arg3	optionnal argument depending on peripheral type

Each peripheral type is defines by a composite index (ptype,subtype). The supported peripheral types and subtypes are defined in the genarch.py file.

The following peripheral components require specific arguments with the following semantic:

	Frame Buffer	Interrupt controller	Generic DMA Controller
ptype	FBF	XCU	MWR
arg0	number of pixels per line	Number of HWI inputs	number of TO_COPROC ports
arg1	number of lines	Number of PTI inputs	number of FROM_COPROC ports
arg2	unused	Number of WTI inputs	number of CONFIG registers
arg3	unused	unused	number of STATUS registers

Hardware coprocessors using the Generic DMA controller to access memory are described as peripherals. They must be defined with the MWR ptype argument, and the subtype argument defines the coprocessor type.

3.5) Interrupt line

The archi.addIrq() is used to describe the hardware interrupts routing from a physical peripheral to an interrupt concentrator. This construct adds one input IRQ line to an XCU peripheral, or to a PIC peripheral. It has the following arguments:

periph	peripheral receiving the IRQ line
index	input port index
isrtype	Interrupt Service Routine type
channel	channel index for multi-channel ISR

The supported ISR types are defined in the genarch.py file.

4) The boot_info_t structure

The ALMOS-MK boot-loader uses the informations found in arch_info.bin to build one boot_info_t structure in each cluster. This generic boot_info_t structure is used by the ALMOS kernel to build in each cluster its own representation of the hardware. Therefore, the boot_info_t structure defines the generic (hardware independent) interface between the hardware specific boot-loader and the kernel.

It is defined in the almos-work/kernel/libk/boot_info.h file.