RE: [PATCH 1/2] arm64: imx8mp: Read MAC address from M24C32-D write-lockable page on DH i.MX8MP DHCOM if available

[Christoph Niedermaier <cniedermaier@dh-electronics.com>]

From: Marek Vasut <marex@denx.de>
Sent: Saturday, October 12, 2024 10:43 PM
> On 10/10/24 3:23 PM, Christoph Niedermaier wrote:
>> The i.MX8M Plus DHCOM currently supports parsing ethernet MAC address
>> from multiple sources in the following priority order:
>>
>> 1) U-Boot environment 'ethaddr'/'eth1addr' environment variable
>> 2) SoC OTP fuses
>> 3) On-SoM EEPROM
>>
>> The new i.MX8M Plus DHCOM rev.200 is populated with M24C32-D EEPROM
>> which contains additional write-lockable page, which can also be
>> populated with a structure containing ethernet MAC address.
>>
>> Add support for parsing the content of this new write-lockable page
>> and place it between 2) and 3) on the priority list. The new entry is
>> 2.5) On-SoM EEPROM write-lockable page
>>
>> Because the write-lockable page is not present on rev.100 i.MX8MP DHCOM
>> SoM, test whether EEPROM ID page exists in DT and whether it is enabled
>> first. If so, read the entire ID page out, validate it, and determine
>> whether EEPROM MAC address is populated in it in DH specific format. If
>> so, use the MAC address. There may be multiple EEPROMs with an ID page
>> on this platform, always use the first one.
>>
>> Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
>> ---
>> Cc: "NXP i.MX U-Boot Team" <uboot-imx@nxp.com>
>> Cc: Marek Vasut <marex@denx.de>
>> Cc: Fabio Estevam <festevam@gmail.com>
>> Cc: Stefano Babic <sbabic@denx.de>
>> Cc: Tom Rini <trini@konsulko.com>
>> Cc: u-boot@dh-electronics.com
>> ---
>>   board/dhelectronics/common/dh_common.c        | 113 ++++++++++++++++++
>>   board/dhelectronics/common/dh_common.h        |  23 ++++
>>   .../dh_imx8mp/imx8mp_dhcom_pdk2.c             |   6 +
>>   3 files changed, 142 insertions(+)
>>
>> diff --git a/board/dhelectronics/common/dh_common.c b/board/dhelectronics/common/dh_common.c
>> index 32c50b4f0f..8ea70fc984 100644
>> --- a/board/dhelectronics/common/dh_common.c
>> +++ b/board/dhelectronics/common/dh_common.c
>> @@ -7,9 +7,22 @@
>>   #include <dm.h>
>>   #include <i2c_eeprom.h>
>>   #include <net.h>
>> +#include <u-boot/crc.h>
>>
>>   #include "dh_common.h"
>>
>> +struct eeprom_id_page {
>> +     u8      id[3];          /* Identifier 'D', 'H', 'E' - 'D' is at index 0 */
>> +     u8      version;        /* 0x10 -- Version 1.0 */
>> +     u8      data_crc16[2];  /* [1] is MSbyte */
>> +     u8      header_crc8;
>> +     u8      mac0[6];
>> +     u8      mac1[6];
>> +     u8      item_prefix;    /* H/F is coded in MSbits, Vendor coding starts at LSbits */
>> +     u8      item_num[3];    /* [2] is MSbyte */
>> +     u8      serial[9];      /* [8] is MSbyte */
>> +} __packed;
> 
> Is __packed needed ?

I want to avoid padding in any case.

Regards
Christoph