On CC254X, I configured the SPI DMA transmission

On CC254X, I configured the SPI DMA transmission:

halDMADesc_t* ch = HAL_DMA_GET_DESC1234(HAL_DMA_CH_TX);
HAL_DMA_ABORT_CH(HAL_DMA_CH_TX);
HAL_DMA_SET_DEST(ch, HAL_DMA_U0DBUF);
HAL_DMA_SET_VLEN(ch, HAL_DMA_VLEN_USE_LEN);
HAL_DMA_SET_WORD_SIZE(ch, HAL_DMA_WORDSIZE_BYTE);
HAL_DMA_SET_TRIG_MODE(ch, HAL_DMA_TMODE_SINGLE);
HAL_DMA_SET_TRIG_SRC(ch, HAL_DMA_TRIG_UTX0);
HAL_DMA_SET_SRC_INC(ch, HAL_DMA_SRCINC_1);
HAL_DMA_SET_SOURCE(ch, buf);
HAL_DMA_SET_DST_INC(ch, HAL_DMA_DSTINC_0);
HAL_DMA_SET_IRQ(ch, HAL_DMA_IRQMASK_ENABLE);
HAL_DMA_SET_M8(ch, HAL_DMA_M8_USE_8_BITS);
HAL_DMA_SET_PRIORITY(ch, HAL_DMA_PRI_HIGH);
HAL_DMA_SET_LEN(ch, len);
HAL_DMA_ABORT_CH(HAL_DMA_CH_TX);
HAL_DMA_ARM_CH(HAL_DMA_CH_TX);
asm("NOP"); asm("NOP"); asm("NOP"); asm("NOP");
asm("NOP"); asm("NOP"); asm("NOP"); asm("NOP"); asm("NOP");
HAL_DMA_MAN_TRIGGER(HAL_DMA_CH_TX);

It can send up to 255 bytes at a time.

Now I want to tranmit more than 256 bytes, that is len > 256, How to configure it? Thanks!