OMAPL138/C6748 AIS Read Benchmarks

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Introduction

This page gives the measurements of the time taken (i.e., Booting time ) to execute the first instruction after power on reset the board. The boot modes of OMAP-L138/OMAPL137/C6748 are experimented and projected them as benchmark measurements. The figure projected here are approximate as it is done under the lab environment.


Boot Performance using AIS read

AIS Read Performance
Board Boot Mode Boot Time (ms)
C6748 LCDK NAND16 37
SD/MMC 200
UART 300
OMAP-L138 LCDK NAND16 120
SD/MMC 2100
UART 300

Test Details

Methodology

The test case used here toggles a GPIO immediately at the start of the first AIS command executed by RBL. AIS read timings were measured from the rising edge of RESETn to the rising/falling edge of the GPIO.

Please note that the measured values are just a bench exercise which includes a little bit of time consumed for AIS support functions to configure the PSC and PINMUX before the GPIO toggling starts.

Software

This test case used a simple LED application. After converting the LED application into an AIS formatted file, it is patched with additional AIS commands. So, now, the AIS commands will be patched in a way that it sits on top of the LED Application file. These AIS commands actually does the following.

1. Configuring GPIO PSC 2. Pinmuxing the GPIO 3. Toggles the GPIO ( The target CPU runs at 24MHz ie bypass frequency.)

Thus, the time is measured between the reset and the first toggling of GPIO. For more information on manually patching AIS file with AIS commands, please refer to the following TI WIKI.

http://processors.wiki.ti.com/index.php/Manually_Patch_AIS_File_using_Perl_Script

Hardware

Test was performed on Revision 2.1 of OMAP-L138/C6748 devices. Boot times may differ greatly from previous revisions for some boot modes.

The board runs at 24MHz ie bypass frequency.

OMAPL138 LCDK Board

Hardware Part Number Frequency
Board OMAPL138 LCDK board -
SoC OMAP-L138 Rev. 2.1 24 MHz
NAND16 SAMSUNG K4T1G1640F-BCE7 16-bit NAND Flash 8MHz
MMC/SD TRANSCEND 8GB micro SD card
12 MHz



C6748 LCDK Board

Hardware Part Number Frequency
Board C6748 LCDK board -
SoC C6748 Rev. 2.1 24 MHz
NAND16 SAMSUNG K4T1G1640F-BCE7 16-bit NAND Flash 8MHz
MMC/SD TRANSCEND 8GB micro SD card
12 MHz


Discussion

The results show that the OMAP-L138 boot times (ARM boot devices) are generally much longer than C6748/OMAP-L137 (DSP boot device) due to the following reasons.

  • The ARM cache is not enabled by default, while the DSP cache is. This means that in the code, especially, delay loops will execute much faster on the DSP.
  • The OMAP-L138/AM1808 require additional time before the ARM bootloader begins executing.
  • The DSP compiler generates fewer instructions for delay loops than the ARM compiler, resulting in faster execution.

For larger boot images on OMAP-L138/AM1808, it would be beneficial to enable the cache through AIS commands. Future versions of AISgen will provide this option.