[PATCH v2] spi: mt65xx: add dual and quad mode for standard spi device

[Tim Kuo <Tim.Kuo@mediatek.com>]

From: "Tim Kuo" <Tim.Kuo@mediatek.com>

Mediatek SPI hardware natively supports dual and quad modes, and these
modes are already enabled for SPI flash devices under spi-mem framework
in MTK SPI controller spi-mt65xx. However, other SPI devices, such as
touch panels, are limited to single mode because spi-mt65xx lacks SPI
mode argument parsing from SPI framework for these SPI devices outside
spi-mem framework.

This patch adds dual and quad mode support for these SPI devices by
introducing a new API, mtk_spi_set_nbits, for SPI mode argument parsing.

Signed-off-by: Tim Kuo <Tim.Kuo@mediatek.com>
---
v2: remove ret and change to use fallthrough in switch

 drivers/spi/spi-mt65xx.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
index 8a3c00c3af42..4b40985af1ea 100644
--- a/drivers/spi/spi-mt65xx.c
+++ b/drivers/spi/spi-mt65xx.c
@@ -563,6 +563,22 @@ static void mtk_spi_setup_packet(struct spi_controller *host)
 	writel(reg_val, mdata->base + SPI_CFG1_REG);
 }
 
+inline u32 mtk_spi_set_nbit(u32 nbit)
+{
+	switch (nbit) {
+	default:
+		pr_warn_once("unknown nbit mode %u. Falling back to single mode\n",
+			     nbit);
+		fallthrough;
+	case SPI_NBITS_SINGLE:
+		return 0x0;
+	case SPI_NBITS_DUAL:
+		return 0x1;
+	case SPI_NBITS_QUAD:
+		return 0x2;
+	}
+}
+
 static void mtk_spi_enable_transfer(struct spi_controller *host)
 {
 	u32 cmd;
@@ -729,10 +745,16 @@ static int mtk_spi_transfer_one(struct spi_controller *host,
 
 	/* prepare xfer direction and duplex mode */
 	if (mdata->dev_comp->ipm_design) {
-		if (!xfer->tx_buf || !xfer->rx_buf) {
+		if (xfer->tx_buf && xfer->rx_buf) {
+			reg_val &= ~SPI_CFG3_IPM_HALF_DUPLEX_EN;
+		} else if (xfer->tx_buf) {
+			reg_val |= SPI_CFG3_IPM_HALF_DUPLEX_EN;
+			reg_val &= ~SPI_CFG3_IPM_HALF_DUPLEX_DIR;
+			reg_val |= mtk_spi_set_nbit(xfer->tx_nbits);
+		} else {
 			reg_val |= SPI_CFG3_IPM_HALF_DUPLEX_EN;
-			if (xfer->rx_buf)
-				reg_val |= SPI_CFG3_IPM_HALF_DUPLEX_DIR;
+			reg_val |= SPI_CFG3_IPM_HALF_DUPLEX_DIR;
+			reg_val |= mtk_spi_set_nbit(xfer->rx_nbits);
 		}
 		writel(reg_val, mdata->base + SPI_CFG3_IPM_REG);
 	}
-- 
2.45.2