spi: ti-qspi: use 128 bit transfer mode where possible
authorVignesh R <vigneshr@ti.com>
Thu, 20 Aug 2015 10:30:59 +0000 (16:00 +0530)
committerMark Brown <broonie@kernel.org>
Thu, 20 Aug 2015 17:56:42 +0000 (10:56 -0700)
TI QSPI has four 32 bit data regsiters which can be used to transfer 16
bytes of data at once. The register group QSPI_SPI_DATA_REG_3,
QSPI_SPI_DATA_REG_2, QSPI_SPI_DATA_REG_1 and QSPI_SPI_DATA_REG is
treated as a single 128-bit word for shifting data in and out. The bit
at QSPI_SPI_DATA_REG_3[31] position is the first bit to be shifted out
in case of 128 bit transfer mode. Therefore the first byte to be written
to flash should be at QSPI_SPI_DATA_REG_3[31-25] position.
Instead of writing 1 byte at a time when interacting with spi-nor flash,
make use of all the four registers so that 16 bytes can be transferred
in one go. This reduces number of register writes and Word Complete
interrupts for a given transfer message size, thereby increasing the
write performance.

Without this patch the raw flash write speed is ~100KB/s, with this
patch the write speed increases to ~400 kB/s on DRA74 EVM.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
drivers/spi/spi-ti-qspi.c

index 5c061687035886e5768bf6031616068906540b04..aa6d284131e0fd99fd19ef92dc0adff73ee18a02 100644 (file)
@@ -99,6 +99,8 @@ struct ti_qspi {
 #define QSPI_INVAL                     (4 << 16)
 #define QSPI_WC_CMD_INT_EN                     (1 << 14)
 #define QSPI_FLEN(n)                   ((n - 1) << 0)
+#define QSPI_WLEN_MAX_BITS             128
+#define QSPI_WLEN_MAX_BYTES            16
 
 /* STATUS REGISTER */
 #define BUSY                           0x01
@@ -217,14 +219,16 @@ static inline u32 qspi_is_busy(struct ti_qspi *qspi)
 
 static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 {
-       int wlen, count;
+       int wlen, count, xfer_len;
        unsigned int cmd;
        const u8 *txbuf;
+       u32 data;
 
        txbuf = t->tx_buf;
        cmd = qspi->cmd | QSPI_WR_SNGL;
        count = t->len;
        wlen = t->bits_per_word >> 3;   /* in bytes */
+       xfer_len = wlen;
 
        while (count) {
                if (qspi_is_busy(qspi))
@@ -234,7 +238,29 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
                case 1:
                        dev_dbg(qspi->dev, "tx cmd %08x dc %08x data %02x\n",
                                        cmd, qspi->dc, *txbuf);
-                       writeb(*txbuf, qspi->base + QSPI_SPI_DATA_REG);
+                       if (count >= QSPI_WLEN_MAX_BYTES) {
+                               u32 *txp = (u32 *)txbuf;
+
+                               data = cpu_to_be32(*txp++);
+                               writel(data, qspi->base +
+                                      QSPI_SPI_DATA_REG_3);
+                               data = cpu_to_be32(*txp++);
+                               writel(data, qspi->base +
+                                      QSPI_SPI_DATA_REG_2);
+                               data = cpu_to_be32(*txp++);
+                               writel(data, qspi->base +
+                                      QSPI_SPI_DATA_REG_1);
+                               data = cpu_to_be32(*txp++);
+                               writel(data, qspi->base +
+                                      QSPI_SPI_DATA_REG);
+                               xfer_len = QSPI_WLEN_MAX_BYTES;
+                               cmd |= QSPI_WLEN(QSPI_WLEN_MAX_BITS);
+                       } else {
+                               writeb(*txbuf, qspi->base + QSPI_SPI_DATA_REG);
+                               cmd = qspi->cmd | QSPI_WR_SNGL;
+                               xfer_len = wlen;
+                               cmd |= QSPI_WLEN(wlen);
+                       }
                        break;
                case 2:
                        dev_dbg(qspi->dev, "tx cmd %08x dc %08x data %04x\n",
@@ -254,8 +280,8 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
                        dev_err(qspi->dev, "write timed out\n");
                        return -ETIMEDOUT;
                }
-               txbuf += wlen;
-               count -= wlen;
+               txbuf += xfer_len;
+               count -= xfer_len;
        }
 
        return 0;