ARM instruction asm for DMB with an option "ST"

What is the correct statement to put ARM instruction DMB (Data Memory Barrier) with an option of “ST”?
Based on: … GHHIE.html

Without the option, this statement works:
asm(" DMB");

I try with:
asm(" DMB ST");

I am getting an error:
{standard input}: Assembler messages:
{standard input}:557: Error: garbage following instruction – `dmb ST’
cc: /opt/qnx650/host/linux/x86/usr/bin/ntoarm-as error 1