AM335x EEPROM dependency in Linux

Matt Denoncour

Hello,

I'm using Processor SDK 2.0.0.1 to develop a kernel and u-boot image for a custom board based on the BBB and I'd like to remove the dependency on the EEPROM. After much digging through the source code I've found the files in:

/ti-processor-sdk-linux-am335x-evm-02.00.01.07/board-support/u-boot-2015.07+gitAUTOINC+5922e09363/board/ti/common/

and

/ti-processor-sdk-linux-am335x-evm-02.00.01.07/board-support/u-boot-2015.07+gitAUTOINC+5922e09363/board/ti/am335x/

which read the EEPROM and configure the U-boot accordingly. I see that it loads the values in EEPROM into the RAM at address OMAP_SRAM_SCRATCH_BOARD_EEPROM_START. Is this needed? Can I just force the board_is_bone_lt() to return true?

If the values in RAM are important what I should put in place of the other parts of the data (rev, config, mac addr's) in the EEPROM structure:

struct ti_am_eeprom {
unsigned int header;
char name[TI_EEPROM_HDR_NAME_LEN];
char version[TI_EEPROM_HDR_REV_LEN];
char serial[TI_EEPROM_HDR_SERIAL_LEN];
char config[TI_EEPROM_HDR_CONFIG_LEN];
char mac_addr[TI_EEPROM_HDR_NO_OF_MAC_ADDR][TI_EEPROM_HDR_ETH_ALEN];
} __attribute__ ((__packed__));

Is there anywhere that helps determine which files needed to be modified to port a custom board? I've searched everywhere and can't find anything that isn't deprecated (old Sitara Linux SDK). It looks like there was some good guides for the pre-devicetree days but I'm having a really hard time finding up-to-date information.

For the Kernel is there any dependency on the EEPROM? If so, can you point me to the files I need to modify? It feels like it would have been taken care of in the devicetree but I'm new to Linux and I don't have my head wrapped around everything yet. I have had success modifying the devicetree on a BBB but I don't know what will happen when the EEPROM is not there.

Thanks,

Matt

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

I will ask the software team to comment.

0 Kemal R. Shakir over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 55345 points

Hello Matt,

Here you can find the I2C ID Memory for AM335X-EVM processors.wiki.ti.com/.../AM335x_General_Purpose_EVM_HW_User_Guide and here for AM335X-EVMSK processors.wiki.ti.com/.../AM335xStarterKitHardwareUsersGuide and use them as reference. Instead of removing the eeprom part of your U-Boot you better hard code the I2C ID Memory settings, since later these changes will be in use if needed.

Best regards,
Kemal

0 Matt Denoncour over 9 years ago in reply to Kemal R. Shakir

Prodigy 200 points

Hi Kemal,

Okay, that's what I ended up doing. I read the values from another Beaglebone Black's EEPROM and roughly copied those. Is there anywhere in the Linux source that I need to do similar things? I have been able to boot up successfully on a BBB on which I lifted the SDA pin to the EEPROM so I think I'm okay, I just don't know if there's something subtle I'm missing.

Thanks,

Matt

0 Ravikiran J J over 8 years ago in reply to Matt Denoncour

Intellectual 640 points

Hi Matt,

Could you share the BBB , EEPROM values ??
I am working on BBB based board.

Thanks and Regards,
Ravikiran

0 Matt Denoncour over 8 years ago in reply to Ravikiran J J

Prodigy 200 points

Hi Ravikiran,

I realize it's been a long time but in case it still helps here's what I did:
in the u-boot source folder/board/ti/am335x/board.c I editted the read_eeprom function as such:

static int __maybe_unused read_eeprom(struct ti_am_eeprom **header)
{
//was: return ti_i2c_eeprom_am_get(-1, CONFIG_SYS_I2C_EEPROM_ADDR, header);
char Name[] = "A335BNLT";
char Ver[] = "000C";
char Ser[] = "011600000001";
char Config[] = "00000000000000000000000000000000";
char mac_addr[] = {0xff,0xff,0xff,0xff,0xff,0xff};
//Force to always report as BBB Rev C
// EEPROM data gets stored in special place in the RAM
*header = DERIVED_EEPROM_START;
(*header)->header = TI_EEPROM_HEADER_MAGIC;
//name is "A335BNLT"

memcpy((*header)->name,Name,8);
memcpy((*header)->version,Ver,8);
memcpy((*header)->serial,Ser,8);
memcpy((*header)->config,Config,8);
memcpy(&(*header)->mac_addr[0][0],mac_addr,6);
memcpy(&(*header)->mac_addr[0][0],mac_addr,6);
memcpy(&(*header)->mac_addr[0][0],mac_addr,6);
return 0;
// ti_am_eeprom structure:
//unsigned int header; //0 4
//char name[8]; //4 8
//char version[4]; //12 4
//char serial[12]; //16 12
//char config[32]; //28 32
//char mac_addr[HDR_NO_OF_MAC_ADDR][HDR_ETH_ALEN]; //60 6
}

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AM335x EEPROM dependency in Linux