+static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
+ struct spi_device *spi,
+ struct spi_transfer *tfr,
+ u32 cs,
+ unsigned long xfer_time_us)
+{
+ struct bcm2835_spi *bs = spi_master_get_devdata(master);
+ unsigned long timeout;
+
+ /* enable HW block without interrupts */
+ bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
+
+ /* fill in the fifo before timeout calculations
+ * if we are interrupted here, then the data is
+ * getting transferred by the HW while we are interrupted
+ */
+ bcm2835_wr_fifo(bs);
+
+ /* set the timeout */
+ timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES;
+
+ /* loop until finished the transfer */
+ while (bs->rx_len) {
+ /* fill in tx fifo with remaining data */
+ bcm2835_wr_fifo(bs);
+
+ /* read from fifo as much as possible */
+ bcm2835_rd_fifo(bs);
+
+ /* if there is still data pending to read
+ * then check the timeout
+ */
+ if (bs->rx_len && time_after(jiffies, timeout)) {
+ dev_dbg_ratelimited(&spi->dev,
+ "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
+ jiffies - timeout,
+ bs->tx_len, bs->rx_len);
+ /* fall back to interrupt mode */
+ return bcm2835_spi_transfer_one_irq(master, spi,
+ tfr, cs);
+ }
+ }
+
+ /* Transfer complete - reset SPI HW */
+ bcm2835_spi_reset_hw(master);
+ /* and return without waiting for completion */
+ return 0;
+}
+