spi: spi-sun6i: sun6i_spi_transfer_one(): enable RF_RDY interrupt only if needed

In sun6i_spi_transfer_one() the RX FIFO Ready (SUN6I_INT_CTL_RF_RDY) is
unconditionally enabled.

A RX interrupt is only needed, if more data than fits into the FIFO is going to
be received during this transfer. As the RX-FIFO is drained during transfer
complete interrupt, enable the RX FIFO Ready interrupt only if the data doesn't
fit into the FIFO.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20200706143443.9855-11-mkl@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index bba9843..19238e1 100644 (file)
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -190,7 +190,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
        unsigned int mclk_rate, div, div_cdr1, div_cdr2, timeout;
        unsigned int start, end, tx_time;
        unsigned int trig_level;
-       unsigned int tx_len = 0;
+       unsigned int tx_len = 0, rx_len = 0;
        int ret = 0;
        u32 reg;
 
@@ -245,10 +245,12 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
         * If it's a TX only transfer, we don't want to fill the RX
         * FIFO with bogus data
         */
-       if (sspi->rx_buf)
+       if (sspi->rx_buf) {
                reg &= ~SUN6I_TFR_CTL_DHB;
-       else
+               rx_len = tfr->len;
+       } else {
                reg |= SUN6I_TFR_CTL_DHB;
+       }
 
        /* We want to control the chip select manually */
        reg |= SUN6I_TFR_CTL_CS_MANUAL;
@@ -302,8 +304,10 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
        sun6i_spi_fill_fifo(sspi);
 
        /* Enable the interrupts */
-       reg = SUN6I_INT_CTL_TC | SUN6I_INT_CTL_RF_RDY;
+       reg = SUN6I_INT_CTL_TC;
 
+       if (rx_len > sspi->fifo_depth)
+               reg |= SUN6I_INT_CTL_RF_RDY;
        if (tx_len > sspi->fifo_depth)
                reg |= SUN6I_INT_CTL_TF_ERQ;