Getting Started Guide for P1020/P1011

Document created by -nilda Employee on Sep 25, 2012
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Table of Contents

 

 

Booting from On-Chip ROM (eSDHC or eSPI)

 

What does on-chip ROM do?


The on-chip ROM includes both an eSDHC device driver and an eSPI driver. The driver code copies data from either an SD card/MMC or from an EEPROM with an SPI interface to a temporary memory location. The on-chip ROM is internally mapped to 0xFFFF_E000 when booting from either an SD card/MMC or from an EEPROM.The on-chip boot ROM code uses the information from the SD card/MMC or the EEPROM to configure a temporary memory, such as the L2 cache or a DDR, before it copies a U-Boot image to this temporary memory. After SD card/MMC- or EEPROM-specific configurations are set up and all the image code is copied, the e500 core jumps to the address specified at offset 0x60 in the configurations and starts to execute the code from the temporary memory.

 

Avoiding On-Chip ROM Configuration Issues Using TLB1


The on-chip ROM code configures the first entry of the table lookaside buffer 1 (TLB1) to access up to 4 Gbytes starting from address 0x0000. Although the user configuration easily copies the image to any specified temporary memory location, it may conflict with the U-Boot configuration.

Building a RAM-Based U-Boot Under Linux

 

Both SD card/MMC and EEPROM booting use the same RAM-based U-Boot image. A RAM-based U-Boot is different from a NOR Flash-based U-Boot in the following ways:

  • A NOR Flash can perform random accesses, but an SD card/MMC or EEPROM cannot be accessed directly.
  • The starting address of the RAM-based U-Boot is different than a NOR Flash-based U-Boot.After copying the U-Boot image to offset 0x58 in the control words section of the data structure, the on-chip ROM jumps to the location specified at offset 0x60. The requirements for building a RAM-based U-Boot under Linux are as follows:
  • Use a compile time header file to assign the starting location for a U-Boot.
  • The initialization code for the U-Boot must be changed to fit the different U-Boot options. Due to the first entry of TLB1 configuration already in the boot ROM code, the RAM-based U-Boot may need to manage different TLBs or need to change the first entry of the TLB1, if necessary.
  • The U-Boot environment variables must be saved to an SD card/MMC or an EEPROM, and the corresponding code dealing with the environment must be changed to save the variables Note that in the Freescale BSP, cmd_nvedit.c and env_common.c are changed, and env_sdcard.c is added to handle the environment variables.

 

Preparing the image using boot_format

boot_format is a booting utility application

 

  • When booting from an SD card/MMC, boot_format puts the configuration file and the RAM-based U-Boot image on the card (Section 4.3, “Putting a Boot Image on an SD Card/MMC”).
  • When booting from an EEPROM, boot_format generates a binary image that is used to boot from this EEPROM(Section 4.4, “Generating a Binary File for eSPI Booting,” and Section 4.5, “Putting a Booting Image on an EEPROM”). boot_format runs under a regular Linux machine and requires a super user mode to run. After typing boot_format, the following information displays:
    [root@b08938-02 new_tool]# ./boot_format

 

Usage: ./boot_format config_file image -sd dev [-o out_config] | -spi out_image

   Where:

config_file: includes boot signature and configuration words

image: the U-Boot image for booting from eSDHC/eSPI

dev: SDCard’s device node (e.g. /dev/sdb, /dev/mmcblk0)

out_image: boot image in SPI mode

out_config: modified configure file for SD mode

 

Generating binary file for eSPI routine


Perform the following sequence of tasks to generate a binary file using boot_format:

  1. Copy the application boot_format to a directory on a Linux machine.
  2. Copy the EEPROM configuration file and the U-Boot image to the same directory as boot_format.
  3. If not logged in as a super user, switch to super user mode using su.
  4. Type ./boot_format config_file image -spi out_image.
  5. Generate the booting image “out_image” that is put on the EEPROM in one of the following ways: — Use the EEPROM writer, which is supplied from EEPROM manufacture or a tool supplier. — Write the booting image to an EEPROM under the Linux environment after booting from another method first.

 

Required POR configurations for booting from on-chip RAM

 

The on-chip ROM code does not set up any local access windows (LAWs). Access to the CCSR address space or the L2 cache does not require a LAW. It is the user’s responsibility to set up a LAW through a control word address/data pair for the desired target address and execution starting address (which is typically in either DDR or local bus memory space). At least one LAW must be configured for successful booting using DDR as the temporary memory.

 

Required Configurations for SD Card/MMC Booting


The configuration settings required to boot from an SD card/MMC are as follows:

  • Ensure that cfg_rom_loc[0:3] (Boot_Rom_Loc) are driven with a value of 0b0111.
  • Only one core can be in booting mode. If your device has multiple cores, all other cores must be in a boot hold-off mode. The CPU boot configuration input, cfg_cpux_boot, should be 0, where x is from 1 to n (n = the number of cores).
  • Booting from the eSDHC interface can occur from different SD card slots if multiple SD card slots are designed on the board. In this case, ensure the appropriate SD card/MMC is selected.

 

For example, on the MPC8536DS board, bit 7 of the SW8 is used to select which SD/MMC slot is used. If SW8[7] = 1, an SD card/MMC must be put to the external SD card/MMC slot (J1). TIP The polarity of the SDHC_CD signal should be active-low.

 

Required Configurations for EEPROM Booting


The configuration settings required to boot from an EEPROM are as follows:

  • Ensure that cfg_rom_loc[0:3] (Boot_Rom_Loc) are driven with a value of 0b0110.
  • Only one core can be in booting mode. If your device has multiple cores, all other cores must be in a boot hold-off mode. The CPU boot configuration input, cfg_cpux_boot, should be 0, where x is from 1 to n (n = the number of cores).
  • The eSPI chip select 0 (SPI_CS[0]) must be connected to the EEPROM that is used for booting. No other chip select can be used for booting. This is because during booting, the eSPI controller is configured to operate in master mode. Booting from the eSPI interface only works with SPI_CS[0].

 

Booting to Linux from an SD Card/MMC

 

To boot to Linux from an SD card/MMC, it is assumed that all following configuration files for booting are in the same directory under a Linux machine:

  • RAM-based U-Boot image (u-boot.bin)
  • Kernel image (uImage)
  • Flat device tree file (p1011ds.dtb)
  • Root file syste (rootfs.ext2.gz.uboot)
  • Latest boot-format Perform the following sequence of tasks to boot to Linux from an SD card/MMC

 

Plug an empty SD card/MMC into the Linux machine.

  • Use Linux command fdisk to create two partitions: one 512-Mbyte FAT16 and one ext2/ext3 with remainder of the available disk size.
  • Use Linux command mkfs to create the FAT file system for the first partition.
  • Use mkfs to create the ext2/ext3 file system for the second partitions
  • Follow the procedure in Section 4.3, “Putting a Boot Image on an SD Card/MMC.”
  • Use boot_format to put the boot image on the card.
  • Put the root file system (rootfs.ext2.gz.uboot) on the second partition using the following commands:

 

— dd if=rootfs.ext2.gz.uboot of=rootfs.gz bs=64 skip=64

— gunzip rootfs.gz

— dd if=rootfs of=/dev/sdc2

 

  • Mount the FAT system (mount /dev/sdc1 /mnt/tmp).
  • Copy the kernel file (cp uImage /mnt/tmp) and flat device tree file (cp p1011ds.dtb /mnt/tmp) to the root directory of the FAT system.
  • Unmount the FAT system (umount /mnt/tmp).

 

TIP After copying the kernel file step is performed properly, all the required files and information are on the SD card/MMC.

 

  • If a Linux desk PC is used:
    • Unplug the SD card/MMC from this PC.
    • Plug the SD card/MMC into a system that is going to boot from this card.
  • Configure the system to boot from an SD card/MMC
  • Stop the U-Boot before it loads the Linux kernel by typing any key.
  • Change the bootcmd parameter by typing the following:

 

setenv sdboot ‘setenv bootargs root=/dev/mmcblk0p2 rw rootfstype=ext2 rootdelay=5

console=ttyS0,115200;mmcinfo; fatload mmc 0:1 1000000 /uImage; fatload mmc 0:1 c00000

/p1011ds.dtb; bootm 1000000 - c00000’

 

  • Save the bootcmd parameter by typing save.
  • Continue to boot the system to the Linux prompt by entering run sdboot.

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