1 files changed, 31 insertions, 12 deletions

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index f92b4a69fffa..05d2d6eb7bfa 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -104,6 +104,7 @@ struct bcm2835aux_spi {
         u8 *rx_buf;
         int tx_len;
         int rx_len;
+        int pending;
 };
 
 static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg)
@@ -120,15 +121,27 @@ static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg,
 static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
 {
         u32 data;
-        int i;
         int count = min(bs->rx_len, 3);
 
         data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
         if (bs->rx_buf) {
-                for (i = 0; i < count; i++)
-                        *bs->rx_buf++ = (data >> (8 * (2 - i))) & 0xff;
+                switch (count) {
+                case 4:
+                        *bs->rx_buf++ = (data >> 24) & 0xff;
+                        /* fallthrough */
+                case 3:
+                        *bs->rx_buf++ = (data >> 16) & 0xff;
+                        /* fallthrough */
+                case 2:
+                        *bs->rx_buf++ = (data >> 8) & 0xff;
+                        /* fallthrough */
+                case 1:
+                        *bs->rx_buf++ = (data >> 0) & 0xff;
+                        /* fallthrough - no default */
+                }
         }
         bs->rx_len -= count;
+        bs->pending -= count;
 }
 
 static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
@@ -151,6 +164,7 @@ static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
 
         /* and decrement length */
         bs->tx_len -= count;
+        bs->pending += count;
 
         /* write to the correct TX-register */
         if (bs->tx_len)
@@ -183,6 +197,7 @@ static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
 
         /* check if we have data to write */
         while (bs->tx_len &&
+               (bs->pending < 12) &&
                (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
                   BCM2835_AUX_SPI_STAT_TX_FULL))) {
                 bcm2835aux_wr_fifo(bs);
@@ -234,6 +249,7 @@ static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
 
         /* fill in tx fifo with data before enabling interrupts */
         while ((bs->tx_len) &&
+               (bs->pending < 12) &&
                (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
                   BCM2835_AUX_SPI_STAT_TX_FULL))) {
                 bcm2835aux_wr_fifo(bs);
@@ -245,8 +261,7 @@ static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
 
 static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
                                             struct spi_device *spi,
-                                            struct spi_transfer *tfr,
-                                            unsigned long xfer_time_us)
+                                        struct spi_transfer *tfr)
 {
         struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
         unsigned long timeout;
@@ -305,7 +320,8 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 {
         struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
         unsigned long spi_hz, clk_hz, speed;
-        unsigned long spi_used_hz, xfer_time_us;
+        unsigned long spi_used_hz;
+        unsigned long long xfer_time_us;
 
         /* calculate the registers to handle
          *
@@ -348,16 +364,19 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
         bs->rx_buf = tfr->rx_buf;
         bs->tx_len = tfr->len;
         bs->rx_len = tfr->len;
+        bs->pending = 0;
 
-        /* calculate the estimated time in us the transfer runs */
-        xfer_time_us = tfr->len
-                * 9 /* clocks/byte - SPI-HW waits 1 clock after each byte */
-                * 1000000 / spi_used_hz;
+        /* calculate the estimated time in us the transfer runs
+         * note that there are are 2 idle clocks after each
+         * chunk getting transferred - in our case the chunk size
+         * is 3 bytes, so we approximate this by 9 bits/byte
+         */
+        xfer_time_us = tfr->len * 9 * 1000000;
+        do_div(xfer_time_us, spi_used_hz);
 
         /* run in polling mode for short transfers */
         if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
-                return bcm2835aux_spi_transfer_one_poll(master, spi, tfr,
-                                                        xfer_time_us);
+                return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
 
         /* run in interrupt mode for all others */
         return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);