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>

1 files changed, 50 insertions, 0 deletions

diff --git a/drivers/spi/spi-sirf.c b/drivers/spi/spi-sirf.c
index dc962a17f373..a72b8f87a156 100644
--- 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)) {