Introduction to ARM A15 Linux
DSP Platform Software Apps Team
04/19/2013
TI Confidential - NDA Restrictions
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Outline
1. ARM Cortex-A15 Overview
2. ARM A15 Linux Overview
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U-boot
Two Stage Bootloading
Boot Monitor
SMP Boot Sequence
LPAE
Linux Drivers
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ARM A15 Overview
 ARMv7-A Cortex - the latest member of the
Cortex-A series of processors
 1-4x SMP within a single processor cluster
and low power consumption
 Thumb-2 Technology
 TrustZone Security
 Floating Point
 NEON
 Hardware Virtualization
 Large Physical Address Extension (LPAE)
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Thumb-2 Technology
Thumb Mode
 16-bit Thumb instructions vs 32-bit ARM instructions
 Thumb-2 extends with additional 32-bit instructions
Code density similar to Thumb
 up to a 30% reduction in memory to store instructions
Performance similar to the ARM instruction set on
32-bit memory
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TrustZone Security
2 virtual processors backed by hardware based
access control
Enable application core to switch between 2
states (worlds)
Each world can operate independently while using
the same core.
Memory and peripherals are made aware of the
operating world and provide access control
Secure Monitor is code that runs in secure
Monitor mode and processes switches to and
from the secure world
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Floating Point
Vector Floating Point (VFP) is an FPU
coprocessor extension to the ARM architecture
Hardware support for FP operations in half-,
single- and double-precision floating point
arithmetic.
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NEON
Advanced SIMD extension, or Media Processing
Engine (MPE)
A combined 64- and 128-bit SIMD instruction set
Provides acceleration for media and signal
application
NEON hardware shares the same floating-point
registers as used in VFP.
Linux version: 3.6.0, GCC version: Linaro 4.6.3
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Hardware Virtualization
Hardware support for multiple software
environments available on the same physical
processor
Software applications can access the system
capabilities simultaneously
Virtual envrionments are isolated from each other
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LPAE
64-bit “long-descriptor” format for page tables
Supports 40-bit physical address – up to 1TB of
memory
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ARM A15 Linux Overview






U-boot
Two Stage Bootloading
Boot Monitor
SMP Boot Sequence
LPAE
Linux Drivers
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U-Boot
Based on the Universal Boot Loader public project
Program that moves executable from non-volatile
memory to memory and then transfers CPU
control to the newly “loaded” executable
Minimal drivers
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SPI
I2C
UART
NAND
ETH
USB
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Two Stage Bootloading
ROM Boot Loader(RBL) loads Secondary
Program Loader (SPL) from SPI NOR flash
SPL loads and run the second stage boot loader,
a full version of U-Boot) from NOR or NAND
Keystone II – SPI boot mode
 The first 64K of the SPI NOR flash is flashed with SPL
 Followed by U-Boot image
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Boot Monitor
ARM Cortex A15 requires certain functions to be
executed in the PL1 privilege level
Provides secure privilege level execution service
for Linux Kernel code through SMC calls
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Boot Monitor – High level architecture
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Boot Sequence – Primary Core
 RBL is run on Power On reset
 After completion, load and run u-boot in non-secure mode
 Boot Monitor gets installed
 As part of non-secure entry, boot monitor calls the RBL API
through SMC call (SMC #0) passing _init() entry point address.
 RBL enters monitor mode, _init() inits the monitor vector and calls
init() to init Core/CPU specific inits, set the primary/secondary flag,
the Set the secondary core non-secure entry point address
 Back to non-secure mode and booting of linux kernel
 At linux start up, primary core make SMC call to power on each of
the secondary cores
 Primary core waits for secondary cores to boot up and then
proceeds to rest of booting sequence
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Boot Sequence – Secondary Core
 On Power On reset, RBL initializes and enters the
secondary entry point address of the Boot Monitor core
through SMC call (SMC #0)
 RBL enters monitor mode, _init() inits the monitor
vector and calls init() to init Core/CPU specific
inits.
 On return from _init(), it jumps to secondary kernel
entry point address and start booting 2nd instance
of Linux kernel
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LPAE
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DDR3A memory address space 0x08 0000 0000 – 0x09 FFFF FFFF
Cortex-A15 LPAE with 40-bit address bus may access if MMU is on
ARM has only 32-bit effective address bus if MMU is off
To access DDR3A when MMU is off
 MSMC maps first 2GB to 0x00 8000 0000 – 0x00 FFFF FFFF
 The aliased address space can be used when MMU is on or off
 Keystone II does not support cache coherency for the aliased address space
 Default memory property of TCI6638 is 0x8000 0000 size 0x2000 0000
 When U-boot boots the kernel, it can modify the default
start address.
 If mem_lpae=0, U-boot does not modify
 If mem_lpae=1, U-boot sets the start address to 0x08 0000 0000
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Linux Drivers
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GIC IRQ chip driver
Keystone IPC IRQ chip driver
SMP
AEMIF driver
NAND driver
SPI and SPI NOR flash drivers
I2C and EEPROM drivers
Keystone GPIO driver
Keystone IPC GPIO driver
Network driver (NetCP), PktDMA, Packet Accelerator
SGMII driver
QoS driver
USB driver
10Gig Ethernet driver (not validated due to test hardware)
PCIe driver
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Getting Started with MCSDK
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Prerequisite
 K2EVM-HK (Follow Hardware setup guide to make sure you have the
latest BMC updates)
http://processors.wiki.ti.com/index.php/EVMK2H_Hardware_Setup
 User guide: (getting started guide & exploring as well)
http://processors.wiki.ti.com/index.php/MCSDK_User_Guide_for_KeyStone_II
 Download MCSDK:
http://software-dl.ti.com/sdoemb/sdoemb_public_sw/mcsdk/latest/index_FDS.html
 Ubuntu Linux 12.04 LTS machine, set up Proxy (consult IT)
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Install CCS & MCSDK
 1. Install CCSv5.3.0 at <CCS default Installed Directory>.
For processor architecture, make sure "C6x DSP + ARM processors"
is selected.
 2. Install TI KeyStone2 Emupack,
ti_emupack_keystone2_setup_1.0.0.2
If installed on Linux, replace \ with / in this file
/opt/ti/ccsv5/ccs_base/common/targetdb/devices/TCI6638.xml
 3. Install MCSDK 3.00.00.09, same directory as CCS, e.g.: /opt/ti
 4. copy the file tci6638-evm.ccxml from
mcsdk_linux_3_00_00_09/host-tools/loadlin folder
to ~/<user>/ti/CCSTargetConfiguration folder where the CCS saves
the user specific configuration file.
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Build Prerequisite
 Toolchain installation:
Download the gcc-linaro-arm-linux-gnueabi-2012.03-20120326_linux.tar.bz2
from https://launchpad.net/linaro-toolchain-binaries/trunk/2012.03
cd ~/
tar xjf gcc-linaro-arm-linux-gnueabi-2012.03-20120326_linux.tar.bz2
export CROSS_COMPILE=arm-linux-gnueabiexport ARCH=arm
PATH=$HOME/gcc-linaro-arm-linux-gnueabi-2012.03-20120326_linux/bin:$PATH
 Configure git and install packages needed at build time:
sudo apt-get install git-core
sudo apt-get install build-essential subversion ccache sed wget cvs coreutils unzip texinfo
docbook-utils gawk help2man diffstat file g++ texi2html bison flex htmldoc chrpath
libxext-dev xserver-xorg-dev doxygen bitbake uboot-mkimage libncurses5-dev
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Getting started with MCSDK
 Either use prebuilt images or build Uboot, boot
monitor, kernel & file system on your own.
 File systems supported: ramfs, Net mounted file
system, UBIFS. Configure environment variable as
per user’s guide.
 Getting Kernel & file system to boot
 Run applications
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