serial: bcm283x_mu: Support RX buffer

 Since mini uart has very small rx fifo, writing long string can
 cause overrun. To prevent this, this patch appiles buffer for rx
 process.

Change-Id: Ic5bd37875567fe51eb5491b8867f39c1a78de6b9
Signed-off-by: Dongwoo Lee <dwoo08.lee@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>

1 files changed, 52 insertions, 6 deletions

diff --git a/drivers/serial/serial_bcm283x_mu.c b/drivers/serial/serial_bcm283x_mu.c
index 7585f790d2..93f3657543 100644
--- a/drivers/serial/serial_bcm283x_mu.c
+++ b/drivers/serial/serial_bcm283x_mu.c
@@ -47,8 +47,14 @@ struct bcm283x_mu_regs {
 #define BCM283X_MU_LSR_TX_EMPTY		BIT(5)
 #define BCM283X_MU_LSR_RX_READY		BIT(0)
 
+#define BCM283X_MU_RX_BUFFER_LEN	1024
+#define BCM283X_MU_RX_BUFFER_INIT_POS	-1
+
 struct bcm283x_mu_priv {
 	struct bcm283x_mu_regs *regs;
+	int rx_buffer[BCM283X_MU_RX_BUFFER_LEN];
+	int rx_buffer_in_pos;
+	int rx_buffer_out_pos;
 };
 
 static int bcm283x_mu_serial_getc(struct udevice *dev);
@@ -75,19 +81,55 @@ out:
 	return 0;
 }
 
+static inline int bcm283x_mu_rx_buffer_full(struct bcm283x_mu_priv *priv)
+{
+	return !!(priv->rx_buffer_in_pos == BCM283X_MU_RX_BUFFER_LEN - 1);
+}
+
+static inline int bcm283x_mu_rx_buffer_empty(struct bcm283x_mu_priv *priv)
+{
+	return !!(priv->rx_buffer_out_pos == BCM283X_MU_RX_BUFFER_INIT_POS);
+}
+
+static void bcm283x_mu_rx_buffer_put(struct bcm283x_mu_priv *priv, int data)
+{
+	if (bcm283x_mu_rx_buffer_empty(priv))
+		priv->rx_buffer_out_pos++;
+
+	priv->rx_buffer[++priv->rx_buffer_in_pos] = data;
+}
+
+static int bcm283x_mu_rx_buffer_get(struct bcm283x_mu_priv *priv)
+{
+	int data = priv->rx_buffer[priv->rx_buffer_out_pos];
+
+	if (priv->rx_buffer_in_pos == priv->rx_buffer_out_pos) {
+		priv->rx_buffer_in_pos = BCM283X_MU_RX_BUFFER_INIT_POS;
+		priv->rx_buffer_out_pos = BCM283X_MU_RX_BUFFER_INIT_POS;
+	} else {
+		priv->rx_buffer_out_pos++;
+	}
+
+	return data;
+}
+
 static int bcm283x_mu_serial_getc(struct udevice *dev)
 {
 	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
 	struct bcm283x_mu_regs *regs = priv->regs;
-	u32 data;
+	int max_count = 256;
 
-	/* Wait until there is data in the FIFO */
-	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
-		return -EAGAIN;
+	while (readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY) {
+		if (bcm283x_mu_rx_buffer_full(priv) || --max_count == 0)
+			break;
+
+		bcm283x_mu_rx_buffer_put(priv, readl(&regs->io));
+	}
 
-	data = readl(&regs->io);
+	if (bcm283x_mu_rx_buffer_empty(priv))
+		return -EAGAIN;
 
-	return (int)data;
+	return (int)bcm283x_mu_rx_buffer_get(priv);
 }
 
 static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
@@ -186,6 +228,10 @@ static int bcm283x_mu_serial_probe(struct udevice *dev)
 
 	priv->regs = (struct bcm283x_mu_regs *)plat->base;
 
+	priv->rx_buffer_in_pos = BCM283X_MU_RX_BUFFER_INIT_POS;
+	priv->rx_buffer_out_pos = BCM283X_MU_RX_BUFFER_INIT_POS;
+
+
 	return 0;
 }
 #endif