THR
#define LOAD_PER_CPU_BASE(DEST, THR, REG1, REG2, REG3) \
lduh [THR + TI_CPU], REG1; \
#define LOAD_PER_CPU_BASE(DEST, THR, REG1, REG2, REG3)
at91_usart_spi_writeb(aus, THR, tx_buf[len - remaining]);