spi: ti_qspi: use 128 bit transfer mode when writing to flash

TI QSPI has four 32 bit data registers 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.

With this patch, the flash write speed increases from ~250KBs/ to
~650KB/s on DRA74 EVM.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>

diff --git a/drivers/spi/ti_qspi.c b/drivers/spi/ti_qspi.c
index bb72cb03ec24422b22cc9e3d352975b020526841..1e2c432ede66b04b13a4991acd8de16531cedd50 100644 (file)
--- a/drivers/spi/ti_qspi.c
+++ b/drivers/spi/ti_qspi.c
@@ -23,6 +23,9 @@ DECLARE_GLOBAL_DATA_PTR;
 #define QSPI_TIMEOUT                    2000000
 #define QSPI_FCLK                      192000000
 #define QSPI_DRA7XX_FCLK                76800000
+#define QSPI_WLEN_MAX_BITS             128
+#define QSPI_WLEN_MAX_BYTES            (QSPI_WLEN_MAX_BITS >> 3)
+#define QSPI_WLEN_MASK                 QSPI_WLEN(QSPI_WLEN_MAX_BITS)
 /* clock control */
 #define QSPI_CLK_EN                     BIT(31)
 #define QSPI_CLK_DIV_MAX                0xffff
@@ -230,13 +233,34 @@ static int __ti_qspi_xfer(struct ti_qspi_priv *priv, unsigned int bitlen,
 #ifdef CONFIG_AM43XX
        udelay(100);
 #endif
-       while (words--) {
+       while (words) {
+               u8 xfer_len = 0;
+
                if (txp) {
-                       debug("tx cmd %08x dc %08x data %02x\n",
-                             priv->cmd | QSPI_WR_SNGL, priv->dc, *txp);
-                       writel(*txp++, &priv->base->data);
-                       writel(priv->cmd | QSPI_WR_SNGL,
-                              &priv->base->cmd);
+                       u32 cmd = priv->cmd;
+
+                       if (words >= QSPI_WLEN_MAX_BYTES) {
+                               u32 *txbuf = (u32 *)txp;
+                               u32 data;
+
+                               data = cpu_to_be32(*txbuf++);
+                               writel(data, &priv->base->data3);
+                               data = cpu_to_be32(*txbuf++);
+                               writel(data, &priv->base->data2);
+                               data = cpu_to_be32(*txbuf++);
+                               writel(data, &priv->base->data1);
+                               data = cpu_to_be32(*txbuf++);
+                               writel(data, &priv->base->data);
+                               cmd &= ~QSPI_WLEN_MASK;
+                               cmd |= QSPI_WLEN(QSPI_WLEN_MAX_BITS);
+                               xfer_len = QSPI_WLEN_MAX_BYTES;
+                       } else {
+                               writeb(*txp, &priv->base->data);
+                               xfer_len = 1;
+                       }
+                       debug("tx cmd %08x dc %08x\n",
+                             cmd | QSPI_WR_SNGL, priv->dc);
+                       writel(cmd | QSPI_WR_SNGL, &priv->base->cmd);
                        status = readl(&priv->base->status);
                        timeout = QSPI_TIMEOUT;
                        while ((status & QSPI_WC_BUSY) != QSPI_XFER_DONE) {
@@ -246,6 +270,7 @@ static int __ti_qspi_xfer(struct ti_qspi_priv *priv, unsigned int bitlen,
                                }
                                status = readl(&priv->base->status);
                        }
+                       txp += xfer_len;
                        debug("tx done, status %08x\n", status);
                }
                if (rxp) {
@@ -262,9 +287,11 @@ static int __ti_qspi_xfer(struct ti_qspi_priv *priv, unsigned int bitlen,
                                status = readl(&priv->base->status);
                        }
                        *rxp++ = readl(&priv->base->data);
+                       xfer_len = 1;
                        debug("rx done, status %08x, read %02x\n",
                              status, *(rxp-1));
                }
+               words -= xfer_len;
        }
 
        /* Terminate frame */