[PATCH 1/2] configs/j721e_{beaglebone64, evm}_defconfig: reduce fastboot buffer

[Romain Naour]

Using Snagboot's Snagflash tool to flash the SD card using
fastboot-uboot mode on SK-TDA4VM crash u-boot.

Flashing an image.wic.xz file generated by Yocto doesn't work as
expected:

2026-04-25 16:46:21,134 [INFO] flashed 267296768/267296768 bytes
2026-04-25 16:46:21,162 [INFO] Flashing sparse range 10/13
2026-04-25 16:46:21,163 [INFO] Flashing to MMC device...

On the the chunk is bigger that previous one and doesn't fit in the RAM
memory mapping set by the SoC (TDA4VM)

downloading of 267296768 bytes finished
MMC write: dev # 1, block # 2101440, count 522064 ... 522064 blocks written: OK
switch to partitions #0, OK
mmc1 is current device
Starting download of 486944768 bytes

"Synchronous Abort" handler, esr 0x96000046, far 0x9e800000
Indeed, this memory address (0x9e800000) is "reserved"

"bdinfo" allows to notice that 0x9e800000 address is actually
"reserved":

  memory.count = 0x2
  memory[0]      [0x80000000-0xffffffff], 0x80000000 bytes, flags: none
  memory[1]      [0x880000000-0x8ffffffff], 0x80000000 bytes, flags: none
  reserved.count = 0x4
  reserved[0]    [0x9e800000-0xa8ffffff], 0xa800000 bytes, flags: no-map
  reserved[1]    [0xaa000000-0xabbfffff], 0x1c00000 bytes, flags: no-map
  reserved[2]    [0xfce40b30-0xffffffff], 0x31bf4d0 bytes, flags: no-overwrite
  reserved[3]    [0x8ffff7000-0x8ffffffff], 0x9000 bytes, flags: no-notify, no-overwrite

CONFIG_FASTBOOT_BUF_SIZE was initialy set to 0x2F000000 in the u-boot
configuration for the SK-TDA4VM.

With SYS_LOAD_ADDR set to 0x82000000, the end of the fastboot buffer is
at 0xB1000000 and overlap the reserved region[0] and region[1].

In order to avoid writing the first reserved address (0x9e800000) we
have to reduce CONFIG_FASTBOOT_BUF_SIZE to 0x1c800000.

On this platfrom 0x9e800000 is reserved since it's used for optee
(K3_OPTEE_LOAD_ADDR).

(Issue initially reported on Snagboot)
[1] https://github.com/bootlin/snagboot/issues/90

Signed-off-by: Romain Naour <romain.naour at smile.fr>
---
 configs/j721e_beagleboneai64_a72_defconfig | 2 +-
 configs/j721e_evm_a72_defconfig            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configs/j721e_beagleboneai64_a72_defconfig b/configs/j721e_beagleboneai64_a72_defconfig
index dc76504eb83..abb53687ed6 100644
--- a/configs/j721e_beagleboneai64_a72_defconfig
+++ b/configs/j721e_beagleboneai64_a72_defconfig
@@ -97,7 +97,7 @@ CONFIG_DMA_CHANNELS=y
 CONFIG_TI_K3_NAVSS_UDMA=y
 CONFIG_USB_FUNCTION_FASTBOOT=y
 CONFIG_FASTBOOT_BUF_ADDR=0x82000000
-CONFIG_FASTBOOT_BUF_SIZE=0x2F000000
+CONFIG_FASTBOOT_BUF_SIZE=0x1c800000
 CONFIG_FASTBOOT_FLASH=y
 CONFIG_FASTBOOT_FLASH_MMC_DEV=0
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
diff --git a/configs/j721e_evm_a72_defconfig b/configs/j721e_evm_a72_defconfig
index ed94fff0885..dac1c5ec82f 100644
--- a/configs/j721e_evm_a72_defconfig
+++ b/configs/j721e_evm_a72_defconfig
@@ -104,7 +104,7 @@ CONFIG_DMA_CHANNELS=y
 CONFIG_TI_K3_NAVSS_UDMA=y
 CONFIG_USB_FUNCTION_FASTBOOT=y
 CONFIG_FASTBOOT_BUF_ADDR=0x82000000
-CONFIG_FASTBOOT_BUF_SIZE=0x2F000000
+CONFIG_FASTBOOT_BUF_SIZE=0x1c800000
 CONFIG_FASTBOOT_FLASH=y
 CONFIG_FASTBOOT_FLASH_MMC_DEV=0
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
-- 
2.52.0