spi: sirf: provide a shortcut for spi command-data mode

there are many SPI clients which use the following protocal:
step 1: send command bytes to clients(rx buffer is empty)
step 2: send data bytes to clients or receive data bytes from
clients.
SiRFprimaII provides a shortcut for this kind of SPI transfer.
when tx buf is less or equal than 4 bytes and rx buf is null
in a transfer, we think it as 'command' data and use hardware
command register for the transfer.
here we can save some CPU loading than doing both tx and rx
for a normal transfer.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

diff --git a/drivers/spi/spi-sirf.c b/drivers/spi/spi-sirf.c
index dc962a17f373bb34892c0baaa1da2cbe8a8d2903..a72b8f87a156c6b151504de30035081c8514cc3e 100644 (file)
--- a/drivers/spi/spi-sirf.c
+++ b/drivers/spi/spi-sirf.c
@@ -131,6 +131,8 @@
 #define IS_DMA_VALID(x) (x && ALIGNED(x->tx_buf) && ALIGNED(x->rx_buf) && \
        ALIGNED(x->len) && (x->len < 2 * PAGE_SIZE))
 
+#define SIRFSOC_MAX_CMD_BYTES  4
+
 struct sirfsoc_spi {
        struct spi_bitbang bitbang;
        struct completion rx_done;
@@ -161,6 +163,12 @@ struct sirfsoc_spi {
        void *dummypage;
        int word_width; /* in bytes */
 
+       /*
+        * if tx size is not more than 4 and rx size is NULL, use
+        * command model
+        */
+       bool    tx_by_cmd;
+
        int chipselect[0];
 };
 
@@ -259,6 +267,12 @@ static irqreturn_t spi_sirfsoc_irq(int irq, void *dev_id)
 
        writel(spi_stat, sspi->base + SIRFSOC_SPI_INT_STATUS);
 
+       if (sspi->tx_by_cmd && (spi_stat & SIRFSOC_SPI_FRM_END)) {
+               complete(&sspi->tx_done);
+               writel(0x0, sspi->base + SIRFSOC_SPI_INT_EN);
+               return IRQ_HANDLED;
+       }
+
        /* Error Conditions */
        if (spi_stat & SIRFSOC_SPI_RX_OFLOW ||
                        spi_stat & SIRFSOC_SPI_TX_UFLOW) {
@@ -309,6 +323,34 @@ static int spi_sirfsoc_transfer(struct spi_device *spi, struct spi_transfer *t)
 
        writel(SIRFSOC_SPI_INT_MASK_ALL, sspi->base + SIRFSOC_SPI_INT_STATUS);
 
+       /*
+        * fill tx_buf into command register and wait for its completion
+        */
+       if (sspi->tx_by_cmd) {
+               u32 cmd;
+               memcpy(&cmd, sspi->tx, t->len);
+
+               if (sspi->word_width == 1 && !(spi->mode & SPI_LSB_FIRST))
+                       cmd = cpu_to_be32(cmd) >>
+                               ((SIRFSOC_MAX_CMD_BYTES - t->len) * 8);
+               if (sspi->word_width == 2 && t->len == 4 &&
+                               (!(spi->mode & SPI_LSB_FIRST)))
+                       cmd = ((cmd & 0xffff) << 16) | (cmd >> 16);
+
+               writel(cmd, sspi->base + SIRFSOC_SPI_CMD);
+               writel(SIRFSOC_SPI_FRM_END_INT_EN,
+                       sspi->base + SIRFSOC_SPI_INT_EN);
+               writel(SIRFSOC_SPI_CMD_TX_EN,
+                       sspi->base + SIRFSOC_SPI_TX_RX_EN);
+
+               if (wait_for_completion_timeout(&sspi->tx_done, timeout) == 0) {
+                       dev_err(&spi->dev, "transfer timeout\n");
+                       return 0;
+               }
+
+               return t->len;
+       }
+
        if (sspi->left_tx_word == 1) {
                writel(readl(sspi->base + SIRFSOC_SPI_CTRL) |
                        SIRFSOC_SPI_ENA_AUTO_CLR,
@@ -509,6 +551,14 @@ spi_sirfsoc_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
        writel(txfifo_ctrl, sspi->base + SIRFSOC_SPI_TXFIFO_CTRL);
        writel(rxfifo_ctrl, sspi->base + SIRFSOC_SPI_RXFIFO_CTRL);
 
+       if (t && t->tx_buf && !t->rx_buf && (t->len <= SIRFSOC_MAX_CMD_BYTES)) {
+               regval |= (SIRFSOC_SPI_CMD_BYTE_NUM((t->len - 1)) |
+                               SIRFSOC_SPI_CMD_MODE);
+               sspi->tx_by_cmd = true;
+       } else {
+               regval &= ~SIRFSOC_SPI_CMD_MODE;
+               sspi->tx_by_cmd = false;
+       }
        writel(regval, sspi->base + SIRFSOC_SPI_CTRL);
 
        if (IS_DMA_VALID(t)) {