TI81XX PSP FAQ

About This Manual

This document contains Frequently asked questions and their answers provided by PSP experts.Most of the questions answered here are related to TI81XX platform unless specified otherwise.

Modules/Driver

NAND

What is the ECC scheme that is used for ROM code, Uboot, Kernel and File System?

• The ECC schemes across ROM code, Uboot, Kernel and File System have been synchronised. We now support the same ECC scheme (which is 8-bit BCH) from end-to-end.
• This also means that any image (Uboot, Kernel, File System) can be flashed to NAND from the Uboot as well as Kernel, without worrying about encountering ECC mismatch errors.

What File System should I use with 8-bit BCH ECC scheme?

• UBIFS file system should be used with BCH8 ECC. This is because JFFS2 file system requires some space in the OOB area to store it's meta data. When BCH8 ECC scheme is used, the space left in the OOB area is not sufficient to store this JFFS2 meta data. UBIFS file system, on the other hand, does not require any such meta data to be stored in the OOB area.

Where can I find how to build UBIFS file system image?

• http://processors.wiki.ti.com/index.php/UBIFS_Support

Is prefetch support in NAND enabled by default?

• Yes, as prefetch increases the NAND performance by some margin, we have enabled it by default in our NAND driver.

Does the PSP package have subpage support for NAND?

• No, currently subpage support for NAND is not implemented. But we do plan to implement it as we follow our development roadmap for NAND driver.

Uboot Warning: Erase size 0x00002000 smaller than one erase block 0x00020000 Erasing 0x00020000 instead

• The environment size in Uboot is set to 0x2000 (although 0x20000 is the total size given to environment, a smaller size of 0x2000 was used to save internal memory). The erase block size is 0x20000, so no space less than that can be erased on Nand. Hence, although the command tries to erase 0x2000, it ends up erasing 0x20000. But this is not erasing any area on Nand that is allocated for some other use, as we have mentioned the environment size as 0x20000. So, there is no harm that is being caused and the warning can be ignored.

MMC/SD

Does the MMC/SD driver have support for SDXC (SD eXtended Capacity) cards?

• The SD driver is capable of handling SDXC cards since the commands and state machine are compatible with that of SDHC cards. However, the SDXC cards would be limited by the clock rate, as they would be handled at SDHC speeds.
• Since SDXC cards have a higher capacity, the file-system used should be capable of handling a larger volume size. So a file system that can support this should be used.
• For SDXC cards the native ext2 filesystem on Linux should work. If windows PC compatibility is required the ex-FAT will be required and since this is not supported in Linux community we currently don't have plans for taking this up.
• The SDXC support was verified using a 64GB, Class 10, Transcend SDXC card.

How can I add support for multiple MMC/SD instances?

• We request you to refer to our PSP porting guide <http://processors.wiki.ti.com/index.php?title=TI81xx_PSP_Porting_Guide#MMC.2FSD_Driver>

How can I change the transfer type to 8-bit if my board can support it?

• In the board specific file, the MMC/SD card's structure mentions the data transfer type to be used. By default, we set it to 4-bit transfer mode. Changing "MMC_CAP_4_BIT_DATA" to "MMC_CAP_8_BIT_DATA" will support 8-bit transfer mode.

Clock Framework

Changing clock speed

How do change a clock speed in U-Boot?

A: The PLLs used to generate clocks are different on TI816X and TI814X

TI816X

PLL configuration parameters can be found in file "arch/arm/include/asm/arch-ti81xx/clocks_ti816x.h"

Following are the rules to calculate the output frequency:

fo =  [(N * K)/(FREQ * P * M)] * fr

where,

fo = output frequency of a synthesizer
fr  = refrence input clock - osc0 clock 27 MHz
N - feedback multiplier
K - Phase multiplier - is fixed to 8 for TI816X
FREQ - Synthesizer frequency divider(integer+fractional)
P - pre-divider (pre-fvco-div)
M - post-divider (post-fvco-div)

To change main pll config: <syntaxhighlight lang="c">

1. define MAIN_N 56
2. define MAIN_P 0x1

</syntaxhighlight> ARM/MPU: change the following values to change ARM frequency <syntaxhighlight lang="c">

1. define MAIN_INTFREQ2 0xC
2. define MAIN_FRACFREQ2 0x400000
3. define MAIN_MDIV2 0x1

</syntaxhighlight>

Testing Touchscreen Library

To test touch screen library(ts_lib) please make sure you need to export following environment variables <syntaxhighlight lang="c"> export TSLIB_TSDEVICE=/dev/input/event0 export TSLIB_CALIBFILE=/etc/pointercal export TSLIB_CONFFILE=/etc/ts.conf export TSLIB_PLUGINDIR=/usr/lib/ts export TSLIB_FBDEVICE=/dev/fb0 export TSLIB_CONSOLEDEVICE=none

</syntaxhighlight>

Also make sure all the raw modules mentioned in "/etc/ts.conf" are present in "/usr/lib/ts" directory.