I am running the Debian build on a Snapdragon 410 SOM with a custom board.
On the PM8916 datasheet (Pg. 25), it lists the operating conditions for VBAT,VBAT_SNS to be 3.0V(Min), 3.6V(Typ), and 4.5V(Max).
My custom board supplies 3.3V to VBAT,VBAT_SNS on the PMIC.
*Note: This differs from the the typical 3.6V or 3.7V on the dragonboard 410c.
I’ve tested various supply voltages to VBAT,VBAT_SNS on my board.
My board is able to boot completely when I supply above 3.4V.
However, when my voltage is below 3.4V, I get stuck at “pm_driver_init, Start”.
Here is the boot log from serial console when my voltage is below 3.4V:
Format: Log Type - Time(microsec) - Message - Optional Info
Log Type: B - Since Boot(Power On Reset), D - Delta, S - Statistic
S - QC_IMAGE_VERSION_STRING=BOOT.BF.3.0-00261
S - IMAGE_VARIANT_STRING=HAAAANAAA
S - OEM_IMAGE_VERSION_STRING=C-BPATTH
S - Boot Config, 0x000002e1
S - Core 0 Frequency, 0 MHz
B - 1544 - PBL, Start
B - 3488 - bootable_media_detect_entry, Start
B - 45648 - bootable_media_detect_success, Start
B - 45652 - elf_loader_entry, Start
B - 46868 - auth_hash_seg_entry, Start
B - 47078 - auth_hash_seg_exit, Start
B - 61204 - elf_segs_hash_verify_entry, Start
B - 120081 - PBL, End
B - 127551 - SBL1, Start
B - 190899 - pm_device_init, Start
D - 14731 - pm_device_init, Delta
B - 206241 - boot_flash_init, Start
D - 0 - boot_flash_init, Delta
B - 210267 - boot_config_data_table_init, Start
D - 21777 - boot_config_data_table_init, Delta - (0 Bytes)
B - 236588 - CDT version:3,Platform ID:24,Major ID:1,Minor ID:0,Subtype:0
B - 242810 - sbl1_ddr_set_params, Start
B - 246501 - cpr_init, Start
D - 0 - cpr_init, Delta
B - 252113 - Pre_DDR_clock_init, Start
D - 183 - Pre_DDR_clock_init, Delta
D - 0 - sbl1_ddr_set_params, Delta
B - 264618 - pm_driver_init, Start
It appears there is a check at boot (inside SBL code) that prevents the board from booting when VBAT,VBAT_SNS is below 3.4V.
Unfortunately, the current design for my board does have a way to supply 3.4V to VBAT,VBAT_SNS.
Is there any way that I can either request access to the SBL code or request a build be made that allows me to boot below 3.4V?
Thanks!