구차니의 잡동사니 모음

The NEON/VFP unit comes up disabled on power on reset. To enable Neon requires some co-processor commands. Below is the assembly code required to enable NEON/VFP. It is in the gcc type syntax. ARM code tools use a slightly different syntax.

Neon and VFP both support floating point, which should I use?

The VFPv3 is fully compliant with IEEE 754

Neon is not fully compliant with IEEE 754, so it is mainly targeted for multimedia applications

[링크 : http://processors.wiki.ti.com/index.php/Cortex-A8]

A sequence for initializing the VFPU can be found in u-boot source.

.macro init_vfpu

  ldr r0, =(0xF << 20)

  mcr p15, 0, r0, c1, c0, 2

  mov r3, #0x40000000

  .long 0xeee83a10

  /* vmsr FPEXC, r3 */

.endm /* init_vfpu */

[링크 : http://stackoverflow.com/questions/19231197/enable-neon-on-arm-cortex-a-series]

Using the Advanced SIMD and VFP in Secure state and Non-secure state other than Hyp mode

To use the Advanced SIMD and VFP in Secure state and Non-secure state other than Hyp mode, you must first define the NSACR, then define the CPACR and FPEXC registers. See Non-Secure Access Control Register, Coprocessor Access Control Register, and Floating-Point Exception Register.

Kernel mode NEON

================

Introduction

------------

It is possible to use NEON instructions (and in some cases, VFP instructions) in code that runs in kernel mode. However, for performance reasons, the NEON/VFP register file is not preserved and restored at every context switch or taken exception like the normal register file is, so some manual intervention is required. Furthermore, special care is required for code that may sleep [i.e.,may call schedule()], as NEON or VFP instructions will be executed in a non-preemptible section for reasons outlined below.

[링크 : https://www.kernel.org/doc/Documentation/arm/kernel_mode_neon.txt] 

Package                Minimum ver   Installed info

-------                -----------   ---------------

glibc-devel            0             not installed

zlib                   0             not installed

zlib-devel             0             not installed

ncurses-devel          0             not installed

m4                     0             not installed

bison                  0             not installed

 559 $app_checks = {

 560     binutils         => 'ar --version 2>/dev/null',

 561     'gcc-c++'        => 'g++ --version 2>/dev/null',

 562     glibc            => 'ldd --version 2>/dev/null',

 563     'glibc-devel'    => sub { -f '/usr/lib/i386-linux-gnu/libm.so' || -f '/usr/lib/i386-linux-gnu/libz.so'},

 564     'glibc-headers'  => sub { -f '/usr/include/stdio.h' },

 565     'libstdc++' => sub {

 566             return system_nb(<<TXT) == 0;

 567 echo '#include <iostream>

 568 int main() { std::cout << "test"; }' | g++ -x c++ - -o /dev/null

 569 TXT

 570                        },

 571     lkc              => 'mconf -h 2>/dev/null',

 572     ncurses          => 'tic -V 2>/dev/null',

 573     'ncurses-devel'  => sub { -f '/usr/include/ncurses.h' },

 574     'rpm-build'      => sub { `rpmbuild --version 2>/dev/null` },

 575     sudo             => 'sudo -V 2>/dev/null',

 576     tcl              => "echo 'puts \$tcl_patchLevel' | tclsh",

 577     texinfo          => sub {

 578                        warn  "WARNING: you may also need to install:"

 579                             ." tetex-fonts, dialog and textex\n"

 580                          unless  -f '/usr/share/texmf/tex/texinfo/texinfo.tex';

 581                         `makeinfo --version 2>/dev/null`;

 582                     },

 583     zlib         => sub { my @f = (glob('/usr/lib/libz.so*'),

 584                                    glob('/lib/libz.so*'),

 585                                    glob('/lib/i386-linux-gnu/libz.so*')  ); @f > 1 ? 1 : 0 },

 586     'zlib-devel' => sub { -f '/usr/include/zlib.h' },

 587 }; 

$ sudo apt-get install libncurses-dev bison perl libwww-perl alien cvs

$ cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/ltib co -P ltib

$ cd ltib

$ wget https://community.freescale.com/servlet/JiveServlet/downloadBody/93455-102-3-2835/patch-ltib-ubuntu12.04.sh

$ chmod +x patch-ltib-ubuntu12.04.sh

$ ./patch-ltib-ubuntu12.04.sh

$ sudo visudo

interm ALL = NOPASSWD: /usr/bin/rpm, /opt/ltib/usr/bin/rpm

$ ./ltib 

x86 Linux

    Redhat: 7.3, 8.0, 9.0, Enterprise release 4

    Fedora Core: 1, 2, 3, 4, 5, 8

    Debian: 3.1r0 (stable), unstable, 4.0

    Suse: 8.2, 9.1, 9.2, 10.0, 10.2, 10.3

    Ubuntu 6.10, 7.04, 7.10, 8.04

[링크 : http://ltib.org/documentation-LtibFaq]

12.13.4 USB Recovery Mode

USB boot mode is provided as a fail-safe mechanism for writing system firmware to the boot media. The boot mode is not usually entered by the normal methods of setting the boot pins or OTP, the other methods of entering USB boot mode are referred to generally as recovery mode.

An end user can manually start the recovery mode by holding the recovery switch for several seconds while plugging in USB. Holding the recovery switch is defined as reading the i.MX28 PSWITCH input as a 0x3. There are several switch circuits that will produce this input. The loader also automatically starts recovery mode if a nonrecoverableerror is detected from any boot mode other than USB. disabled completely. Attempts to enter USB boot mode through boot pins, OTP, or recovery methods will result in a chip power-down.

[링크 : http://cache.freescale.com/...=pdf&WT_ASSET=Documentation&fileExt=.pdf]

#define ERROR_DDI_SD_MMC_DEVICE_NOT_SUPPORTED (ERROR_DDI_GROUP | ERROR_DDI_SD_DRIVER_GROUP | 0x14)

0x8020A014 ?

#define ERROR_DDI_SD_MBR_NOT_FOUND (ERROR_DDI_GROUP | ERROR_DDI_SD_DRIVER_GROUP | 0x1D)

0x8020A01D ?

 /***********************************************************************