RX_BUF_L
stm32_ports[id].last_res = RX_BUF_L;
dma_free_coherent(&pdev->dev, RX_BUF_L, stm32port->rx_buf,
stm32port->rx_buf = dma_alloc_coherent(dev, RX_BUF_L,
dma_start = stm32_port->rx_buf + (RX_BUF_L - stm32_port->last_res);
stm32_port->last_res = RX_BUF_L;
stm32_port->last_res = RX_BUF_L;
RX_BUF_L, RX_BUF_P,
#define RX_BUF_P (RX_BUF_L / 2) /* dma rx buffer period */
#define TX_BUF_L RX_BUF_L /* dma tx buffer length */