Finally I get this SPI external add on card, I tried more than 15 times, booting from the SPI Flash, run to 2011R1-RC3 uImage, telnet to connect to the target board and "reboot", I see no fail. Attached the boot log. I can not reproduce your issue at this moment, are you able to narrow down your problem?
U-Boot 2013.07 (ADI-2013R1-pre)-g0fe2585-dirty (Dec 02 2013 - 13:51:52)
CPU: ADSP bf537-0.2 (Detected Rev: 0.2) (spi flash boot)
Board: ADI BF537 stamp board
Support: http://blackfin.uclinux.org/
Clock: VCO: 500 MHz, Core: 500 MHz, System: 125 MHz
RAM: 64 MiB
Flash: 4 MiB
MMC:
****** spi_claim_bus: bus:0 cs:1
SF: Detected M25P64 with page size 64 KiB, total 8 MiB
######## spi_release_bus: bus:0 cs:1
****** spi_claim_bus: bus:0 cs:1
######## spi_release_bus: bus:0 cs:1
In: serial
Out: serial
Err: serial
KGDB: [on serial] ready
Net: bfin_mac
Hit any key to stop autoboot: 0
Using bfin_mac device
TFTP from server 10.99.24.90; our IP address is 10.99.24.142
Filename 'uImage.537.2011R1RC3'.
Load address: 0x1000000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#
1.9 MiB/s
done
Bytes transferred = 4771050 (48ccea hex)
## Booting kernel from Legacy Image at 01000000 ...
Image Name: bf537-0.2-3.0.8-ADI-2011R1
Created: 2011-12-15 10:02:02 UTC
Image Type: Blackfin Linux Kernel Image (gzip compressed)
Data Size: 4770986 Bytes = 4.5 MiB
Load Address: 00001000
Entry Point: 001b3c48
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Starting Kernel at = 001b3c48
Linux version 3.0.8-ADI-2011R1 (sonic@nine) (gcc version 4.3.5 (ADI-devonshire-trunk/git-e17353b) ) #12 Thu Dec 15 18:01:58 CST 2011
register early platform devices
bootconsole [early_shadow0] enabled
bootconsole [early_BFuart0] enabled
early printk enabled on early_BFuart0
Limiting kernel memory to 56MB due to anomaly 05000263
Board Memory: 64MB
Kernel Managed Memory: 64MB
Memory map:
fixedcode = 0x00000400-0x00000490
text = 0x00001000-0x00128350
rodata = 0x00128350-0x00188a80
bss = 0x00189000-0x00198b20
data = 0x00198b20-0x001ac000
stack = 0x001aa000-0x001ac000
init = 0x001ac000-0x008ce000
available = 0x008ce000-0x03800000
DMA Zone = 0x03f00000-0x04000000
Hardware Trace active and enabled
Boot Mode: 3
Reset caused by Software reset
Blackfin support (C) 2004-2010 Analog Devices, Inc.
Compiled for ADSP-BF537 Rev 0.2
Blackfin Linux support by http://blackfin.uclinux.org/
Processor Speed: 500 MHz core clock and 125 MHz System Clock
NOMPU: setting up cplb tables
Instruction Cache Enabled for CPU0
External memory: cacheable in instruction cache
Data Cache Enabled for CPU0
External memory: cacheable (write-back) in data cache
Built 1 zonelists in Zone order, mobility grouping off. Total pages: 14224
Kernel command line: root=/dev/mtdblock0 rw clkin_hz=25000000 earlyprintk=serial,uart0,57600 console=ttyBF0,57600 ip=10.99.24.142:10.99.24.90:10.99.24.1:255.255.255.0:bf537-stamp:eth0:off
PID hash table entries: 256 (order: -2, 1024 bytes)
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
Memory available: 47720k/65536k RAM, (7304k init code, 1180k kernel code, 528k data, 1024k dma, 7780k reserved)
NR_IRQS:146
Configuring Blackfin Priority Driven Interrupts
console [ttyBF0] enabled, bootconsole disabled
console [ttyBF0] enabled, bootconsole disabled
Calibrating delay loop... 995.32 BogoMIPS (lpj=1990656)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 512
Blackfin Scratchpad data SRAM: 4 KB
Blackfin L1 Data A SRAM: 16 KB (16 KB free)
Blackfin L1 Data B SRAM: 16 KB (16 KB free)
Blackfin L1 Instruction SRAM: 48 KB (35 KB free)
NET: Registered protocol family 16
Blackfin DMA Controller
stamp_init(): registering device resources
bio: create slab <bio-0> at 0
bfin-spi bfin-spi.0: Blackfin on-chip SPI Controller Driver, Version 1.0, regs@ffc00500, dma channel@7
Switching to clocksource bfin_cs_cycles
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 2048 (order: 2, 16384 bytes)
TCP bind hash table entries: 2048 (order: 1, 8192 bytes)
TCP: Hash tables configured (established 2048 bind 2048)
TCP reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
NET: Registered protocol family 1
debug-mmrs: setting up Blackfin MMR debugfs
msgmni has been set to 93
io scheduler noop registered (default)
bfin-uart: Blackfin serial driver
bfin-uart.0: ttyBF0 at MMIO 0xffc00400 (irq = 18) is a BFIN-UART
brd: module loaded
bfin_mii_bus: probed
bfin_mac: attached PHY driver [SMSC LAN83C185] (mii_bus:phy_addr=0:01, irq=-1, mdc_clk=2500000Hz(mdc_div=24)@sclk=125MHz)
bfin_mac bfin_mac.0: eth0: Blackfin on-chip Ethernet MAC driver, Version 1.1
rtc-bfin rtc-bfin: rtc core: registered rtc-bfin as rtc0
bfin-wdt: initialized: timeout=20 sec (nowayout=0)
TCP cubic registered
NET: Registered protocol family 17
rtc-bfin rtc-bfin: setting system clock to 1970-01-03 12:45:44 UTC (218744)
IP-Config: Complete:
device=eth0, addr=10.99.24.142, mask=255.255.255.0, gw=10.99.24.1,
host=bf537-stamp, domain=, nis-domain=(none),
bootserver=10.99.24.90, rootserver=10.99.24.90, rootpath=
dma_alloc_init: dma_page @ 0x02947000 - 256 pages at 0x03f00000
Freeing unused kernel memory: 7304k freed