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L138 SD Card Boot & AISgen
Added by Richard Miller-Smith over 12 years ago
Hi,
We're trying to create an SD card that contains both u-boot and our Linux kernel for an L138 module. We've now got our own baseboard, but it is very similar to the IndustrialIO board.
I've read the TI wiki pages on SD boot (http://processors.wiki.ti.com/index.php/OMAP-L138_Preparing_SD_Card_for_Boot) and the bootloader app note (http://www.ti.com/lit/an/sprab41d/sprab41d.pdf). I think we've followed the instructions and have the correct configuration of the Boot lines, but I'm not seeing any sign of life. I suspect that I haven't got the correct settings in AISgen for a MityDSP module, do you have any experience or advice on how these should be set?
Thanks,
Richard
Replies (3)
RE: L138 SD Card Boot & AISgen - Added by Michael Williamson over 12 years ago
Hi Richard,
Can you confirm you using a SOM without an FPGA?
FPGA based SOMs do not expose the bootmode / bootconfig pins necessary to boot directly out of SD. Those modules only support booting from SPI NOR or from UART via the ext-boot pin on the connector.
Modules without FPGA do expose the boot configuration pins, but I don't think we've tested using alternate boot media for the first stage (UBL) and second stage (u-Boot) images. We may still be strapping the boot-pins on the module -- looking at the schematic I'm wondering if those strapping resistors should be no-pops and you are seeing contention. The resistors R54-R62 strap 4.7k resistors to either +3.3V or Ground to LCD_D[8..15], respectively, based on the EXT_BOOT signal. The resistors are on the back side of the module and should be near the edge connector. You need to overcome these with external resistors to change the boot media.
If EXT_BOOT is high you get "0001100" for SPI1 NOR flash.
If EXT_BOOT is low you get "00010111" for UART1 load.
If you can check the levels with a scope (or connect with a JTAG emulator and look at the bootmode register), my guess is that there might contention with your external pull resistors. What value are you using?
Also, the memory and clock configuration for the MityDSP-L138 (i.e., the UBL mDDR setup code) is not the same as with the OMAP-L138 EVM from TI. Are you using the UBL software provided by CL?
-Mike
RE: L138 SD Card Boot & AISgen - Added by Richard Miller-Smith over 12 years ago
Hi Mike,
Thanks for getting back to me so quickly.
We are indeed using a non-FPGA SOM. We have DIP switches on our baseboard to let us set the Boot[4..1] pins and changing these certainly changes the boot behaviour. Pull-ups are 1k, pull-downs are 4k7. Switching to SD boot from SPI boot only alters Boot4 (from low to high) to change the boot pins to "00011100". Checking with a scope shows that Boot4 is at 2.7V.
I'm not touching the UBL, so my understanding is that this should just work as before. But your comments do make me think that the problem is most likely to be in the AISgen settings, as this also seems to need to know the memory and clock configuration. Any clues on how it should be configured gratefully received!
Richard
RE: L138 SD Card Boot & AISgen - Added by Michael Williamson over 12 years ago
I don't have a bunch of time to wander off on this, but you might check the the DEVICE_INIT() routine of the $MDK/sw/3rdparty/OMAP-L138_FlashAndBootUtils_2_27/OMAP-L138/Common/src/device.c file. This has the PLL and DDR initialization code which might correspond to the AISgen settings you need. Just keep in mind the platform definition is "OMAPL138", not "OMAPL138_INDUSTRIAL_IO" (this is used to support a profibus timing configuration, a non-standard mode of operation0.
-Mike
