[PATCH] spi: sh-msiof: Add reset of registers before starting transfer

[Geert Uytterhoeven <geert+renesas@xxxxxxxxx>]

From: Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@xxxxxxxxxxx>

In accordance with hardware specification Ver 1.0, reset register
transmission / reception setting before transfer.

Signed-off-by: Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@xxxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
 drivers/spi/spi-sh-msiof.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c
index b20e70a2bdd115d7..6e83368874839d09 100644
--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -130,6 +130,8 @@ struct sh_msiof_spi_priv {
 #define CTR_TFSE	0x00004000 /* Transmit Frame Sync Signal Output Enable */
 #define CTR_TXE		0x00000200 /* Transmit Enable */
 #define CTR_RXE		0x00000100 /* Receive Enable */
+#define CTR_TXRST	0x00000002 /* Transmit Reset */
+#define CTR_RXRST	0x00000001 /* Receive Reset */
 
 /* FCTR */
 #define FCTR_TFWM_MASK	0xe0000000 /* Transmit FIFO Watermark */
@@ -246,6 +248,25 @@ static irqreturn_t sh_msiof_spi_irq(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static void sh_msiof_spi_reset_regs(struct sh_msiof_spi_priv *p)
+{
+	u32 mask = CTR_TXRST | CTR_RXRST;
+	u32 data;
+	int k;
+
+	data = sh_msiof_read(p, CTR);
+	data |= mask;
+
+	sh_msiof_write(p, CTR, data);
+
+	for (k = 100; k > 0; k--) {
+		if (!(sh_msiof_read(p, CTR) & mask))
+			break;
+
+		udelay(1);
+	}
+}
+
 static const u32 sh_msiof_spi_div_array[] = {
 	SCR_BRDV_DIV_1, SCR_BRDV_DIV_2,	 SCR_BRDV_DIV_4,
 	SCR_BRDV_DIV_8,	SCR_BRDV_DIV_16, SCR_BRDV_DIV_32,
@@ -925,6 +946,9 @@ static int sh_msiof_transfer_one(struct spi_controller *ctlr,
 	bool swab;
 	int ret;
 
+	/* reset registers */
+	sh_msiof_spi_reset_regs(p);
+
 	/* setup clocks (clock already enabled in chipselect()) */
 	if (!spi_controller_is_slave(p->ctlr))
 		sh_msiof_spi_set_clk_regs(p, clk_get_rate(p->clk), t->speed_hz);
-- 
2.17.1