OptimusBlackBootloader » History » Revision 9
Revision 8 (Paul Kocialkowski, 02/08/2016 08:22 PM) → Revision 9/16 (Paul Kocialkowski, 04/03/2016 08:40 AM)
h1. Optimus Black bootloader
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The Optimus Black comes with a bootrom and a set of two bootloaders. The bootrom is stored read-only on the OMAP3630 SoC chip. It loads the first bootloader, which loads the second bootloader.
More information on the booting sequence is available on the OMAP36xx Technical Reference Manual section 26 (Initialization).
h2. Boot device priority
According to the OMAP36xx Technical Reference Manual, section 26.4.4.3 (Booting Device List Setup), the OMAP3630 platform will first choose devices to boot from based on the software booting configuration. If no valid software booting configuration is found, it will read the status of the SYS_BOOT pins to determine the boot device priority order.
h3. Software booting configuration
According to the OMAP36xx Technical Reference Manual, section 26.4.4.4 (Software Booting Configuration), Configuration) the software booting configuration is a data structure stored in scratchpad memory, at address 0x48002910. It is not cleared at reset and can be written with a valid structure before reboot, to take effect.
h3. CONTROL_STATUS register
According to the OMAP36xx Technical Reference Manual, table 13-109 (CONTROL_STATUS), the CONTROL_STATUS register provides the values of the SYS_BOOT pins as sampled at reset time. It is located at address: 0x480022f0.
The register value can be read using:
<pre>
$ devmem 0x480022f0 8
0x25
</pre>
h3. SYS_BOOT resistors
According to the OMAP36xx Technical Reference Manual, section 26.2.3 (Boot Configuration), the SYS_BOOT[5:0] pins are used to select the boot device priority. SYS_BOOT5 indicates whether peripheral booting is preferred.
According to the Optimus Black (P970) Service Manual:
!p970_sys_boot.png!
Some of the resistors framed on the schematics were found not to be populated on the board. The actual layout is the following:
| |_. SYS_BOOT5 |_. SYS_BOOT4 |_. SYS_BOOT3 |_. SYS_BOOT2 |_. SYS_BOOT1 |_. SYS_BOOT0 |
| Pull-up resistor | R316 | N/A | N/A | R314 | N/A | R318 |
| Pull-down resistor | R323 | R322 | R321 | N/A | R319 | N/A |
| Boolean value | 0 | 0 | 0 | 1 | 0 | 1 |
h3. First boot device
According to the OMAP36xx Technical Reference Manual, section 26.2.3 (Boot Configuration), such a value (0x05) indicates MMC2 as first boot device and USB as second boot device.
h2. USB boot
h3. Hardware setup
h3. Software setup
h2. Factory bootloaders
h2. U-Boot
h2. References
* "Optimus Black (P970) Service Manual and Schematics":http://www.cpkb.org/wiki/LG_P970_Optimus_Black_service_manual
* "OMAP36xx Technical Reference Manual":http://www.ti.com/lit/pdf/swpu177
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