ScanManager : read IDCode

Dear support,

On a SoC (Cyclone V) we want to access the JTAG chain from HPS through the ScanManager.

The procedure below is extracted from the documentation and is executed on U-Boot but no data is present in the "Read FIFO". Any help appreciated :

mw 0xFFF02004 0x80 # Enable scan chain 7 : SCANMGR_OFFSET_EN = 1
mw 0xFFD040A0 0xFF7 # Disable TCK clock
mw 0xFFD08030 1 # Connect FPGA JTAG pins
mw 0xFFD040A0 0xFFF # Enable TCK clock

mw 0xFFF02000 0x2 # Reset TAP
mw 0xFFF02000 0x0 # Release reset TAP

# GOSTATE IDLE : write FIFO4BYTE 0x40404040 (TMS = 1111 1111)
mw 0xFFF0201C 0x40404040
mw 0xFFF0201C 0x40404040

# GOSTATE SHIFT_DR : write FIFO4BYTE 0x00400000 (TMS = 0100)
mw 0xFFF0201C 0x00400000

# Output IDCODE : write 8x FIFO4BYTE 0x90909090 : 32 x (TMS = 0, TDI = 1)
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090
mw 0xFFF0201C 0x90909090

# Read FIFOCNT : bits[26:24] = 0 => FAIL !
md 0xFFF02000 1

Regards,

WabG