spi: s3c64xx: support interrupt based pio mode

Support interrupt based pio mode to optimize cpu usage.
When transmitting data size is larget than 32 bytes, operates with
interrupt based pio mode.

By using the FIFORDY INT, an interrupt can be triggered when
the desired size of data has been received. Using this, we can support
interrupt based pio mode.

Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com
Link: https://lore.kernel.org/r/20230502062813.112434-4-jaewon02.kim@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org

drivers/spi/spi-s3c64xx.c

@@ -58,6 +58,8 @@
 #define S3C64XX_SPI_MODE_BUS_TSZ_HALFWORD	(1<<17)
 #define S3C64XX_SPI_MODE_BUS_TSZ_WORD		(2<<17)
 #define S3C64XX_SPI_MODE_BUS_TSZ_MASK		(3<<17)
+#define S3C64XX_SPI_MODE_RX_RDY_LVL		GENMASK(16, 11)
+#define S3C64XX_SPI_MODE_RX_RDY_LVL_SHIFT	11
 #define S3C64XX_SPI_MODE_SELF_LOOPBACK		(1<<3)
 #define S3C64XX_SPI_MODE_RXDMA_ON		(1<<2)
 #define S3C64XX_SPI_MODE_TXDMA_ON		(1<<1)
@@ -114,6 +116,8 @@
 
 #define S3C64XX_SPI_TRAILCNT		S3C64XX_SPI_MAX_TRAILCNT
 
+#define S3C64XX_SPI_POLLING_SIZE	32
+
 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
 #define is_polling(x)	(x->cntrlr_info->polling)
 
@@ -552,7 +556,7 @@ static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
 }
 
 static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
-				struct spi_transfer *xfer)
+				struct spi_transfer *xfer, bool use_irq)
 {
 	void __iomem *regs = sdd->regs;
 	unsigned long val;
@@ -573,6 +577,12 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
 	if (RX_FIFO_LVL(status, sdd) < xfer->len)
 		usleep_range(time_us / 2, time_us);
 
+	if (use_irq) {
+		val = msecs_to_jiffies(ms);
+		if (!wait_for_completion_timeout(&sdd->xfer_completion, val))
+			return -EIO;
+	}
+
 	val = msecs_to_loops(ms);
 	do {
 		status = readl(regs + S3C64XX_SPI_STATUS);
@@ -735,10 +745,13 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
 	void *rx_buf = NULL;
 	int target_len = 0, origin_len = 0;
 	int use_dma = 0;
+	bool use_irq = false;
 	int status;
 	u32 speed;
 	u8 bpw;
 	unsigned long flags;
+	u32 rdy_lv;
+	u32 val;
 
 	reinit_completion(&sdd->xfer_completion);
 
@@ -759,17 +772,46 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
 	    sdd->rx_dma.ch && sdd->tx_dma.ch) {
 		use_dma = 1;
 
-	} else if (xfer->len > fifo_len) {
+	} else if (xfer->len >= fifo_len) {
 		tx_buf = xfer->tx_buf;
 		rx_buf = xfer->rx_buf;
 		origin_len = xfer->len;
-
 		target_len = xfer->len;
-		if (xfer->len > fifo_len)
-			xfer->len = fifo_len;
+		xfer->len = fifo_len - 1;
 	}
 
 	do {
+		/* transfer size is greater than 32, change to IRQ mode */
+		if (xfer->len > S3C64XX_SPI_POLLING_SIZE)
+			use_irq = true;
+
+		if (use_irq) {
+			reinit_completion(&sdd->xfer_completion);
+
+			rdy_lv = xfer->len;
+			/* Setup RDY_FIFO trigger Level
+			 * RDY_LVL =
+			 * fifo_lvl up to 64 byte -> N bytes
+			 *               128 byte -> RDY_LVL * 2 bytes
+			 *               256 byte -> RDY_LVL * 4 bytes
+			 */
+			if (fifo_len == 128)
+				rdy_lv /= 2;
+			else if (fifo_len == 256)
+				rdy_lv /= 4;
+
+			val = readl(sdd->regs + S3C64XX_SPI_MODE_CFG);
+			val &= ~S3C64XX_SPI_MODE_RX_RDY_LVL;
+			val |= (rdy_lv << S3C64XX_SPI_MODE_RX_RDY_LVL_SHIFT);
+			writel(val, sdd->regs + S3C64XX_SPI_MODE_CFG);
+
+			/* Enable FIFO_RDY_EN IRQ */
+			val = readl(sdd->regs + S3C64XX_SPI_INT_EN);
+			writel((val | S3C64XX_SPI_INT_RX_FIFORDY_EN),
+					sdd->regs + S3C64XX_SPI_INT_EN);
+
+		}
+
 		spin_lock_irqsave(&sdd->lock, flags);
 
 		/* Pending only which is to be done */
@@ -791,7 +833,7 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
 		if (use_dma)
 			status = s3c64xx_wait_for_dma(sdd, xfer);
 		else
-			status = s3c64xx_wait_for_pio(sdd, xfer);
+			status = s3c64xx_wait_for_pio(sdd, xfer, use_irq);
 
 		if (status) {
 			dev_err(&spi->dev,
@@ -830,8 +872,8 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
 			if (xfer->rx_buf)
 				xfer->rx_buf += xfer->len;
 
-			if (target_len > fifo_len)
-				xfer->len = fifo_len;
+			if (target_len >= fifo_len)
+				xfer->len = fifo_len - 1;
 			else
 				xfer->len = target_len;
 		}
@@ -1001,6 +1043,14 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data)
 		dev_err(&spi->dev, "TX underrun\n");
 	}
 
+	if (val & S3C64XX_SPI_ST_RX_FIFORDY) {
+		complete(&sdd->xfer_completion);
+		/* No pending clear irq, turn-off INT_EN_RX_FIFO_RDY */
+		val = readl(sdd->regs + S3C64XX_SPI_INT_EN);
+		writel((val & ~S3C64XX_SPI_INT_RX_FIFORDY_EN),
+				sdd->regs + S3C64XX_SPI_INT_EN);
+	}
+
 	/* Clear the pending irq by setting and then clearing it */
 	writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR);
 	writel(0, sdd->regs + S3C64XX_SPI_PENDING_CLR);