X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=drivers%2Fserial%2Fserial_sifive.c;h=c142ccdf3d57bb376496b88da95fc67570b9a1ec;hb=75214b051bfbbdafa5134b4320b9e4ae6ee9b22d;hp=341728a690fd292f71b7da0dfe859599bce2d7f7;hpb=7e40d0a38fc42de12696c835eded8945d650bfc1;p=oweals%2Fu-boot.git

diff --git a/drivers/serial/serial_sifive.c b/drivers/serial/serial_sifive.c
index 341728a690..c142ccdf3d 100644
--- a/drivers/serial/serial_sifive.c
+++ b/drivers/serial/serial_sifive.c
@@ -3,8 +3,8 @@
  * Copyright (C) 2018 Anup Patel <anup@brainfault.org>
  */
 
-#include <clk.h>
 #include <common.h>
+#include <clk.h>
 #include <debug_uart.h>
 #include <dm.h>
 #include <errno.h>
@@ -22,6 +22,9 @@ DECLARE_GLOBAL_DATA_PTR;
 #define UART_TXCTRL_TXEN	0x1
 #define UART_RXCTRL_RXEN	0x1
 
+/* IP register */
+#define UART_IP_RXWM            0x2
+
 struct uart_sifive {
 	u32 txfifo;
 	u32 rxfifo;
@@ -33,16 +36,39 @@ struct uart_sifive {
 };
 
 struct sifive_uart_platdata {
-	unsigned int clock;
-	int saved_input_char;
+	unsigned long clock;
 	struct uart_sifive *regs;
 };
 
+/**
+ * Find minimum divisor divides in_freq to max_target_hz;
+ * Based on uart driver n SiFive FSBL.
+ *
+ * f_baud = f_in / (div + 1) => div = (f_in / f_baud) - 1
+ * The nearest integer solution requires rounding up as to not exceed
+ * max_target_hz.
+ * div  = ceil(f_in / f_baud) - 1
+ *	= floor((f_in - 1 + f_baud) / f_baud) - 1
+ * This should not overflow as long as (f_in - 1 + f_baud) does not exceed
+ * 2^32 - 1, which is unlikely since we represent frequencies in kHz.
+ */
+static inline unsigned int uart_min_clk_divisor(unsigned long in_freq,
+						unsigned long max_target_hz)
+{
+	unsigned long quotient =
+			(in_freq + max_target_hz - 1) / (max_target_hz);
+	/* Avoid underflow */
+	if (quotient == 0)
+		return 0;
+	else
+		return quotient - 1;
+}
+
 /* Set up the baud rate in gd struct */
 static void _sifive_serial_setbrg(struct uart_sifive *regs,
 				  unsigned long clock, unsigned long baud)
 {
-	writel((u32)((clock / baud) - 1), &regs->div);
+	writel((uart_min_clk_divisor(clock, baud)), &regs->div);
 }
 
 static void _sifive_serial_init(struct uart_sifive *regs)
@@ -70,32 +96,32 @@ static int _sifive_serial_getc(struct uart_sifive *regs)
 		return -EAGAIN;
 	ch &= UART_RXFIFO_DATA;
 
-	return (!ch) ? -EAGAIN : ch;
+	return ch;
 }
 
 static int sifive_serial_setbrg(struct udevice *dev, int baudrate)
 {
-	int err;
+	int ret;
 	struct clk clk;
 	struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
+	u32 clock = 0;
 
-	err = clk_get_by_index(dev, 0, &clk);
-	if (!err) {
-		err = clk_get_rate(&clk);
-		if (!IS_ERR_VALUE(err))
-			platdata->clock = err;
-	} else if (err != -ENOENT && err != -ENODEV && err != -ENOSYS) {
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (IS_ERR_VALUE(ret)) {
 		debug("SiFive UART failed to get clock\n");
-		return err;
-	}
-
-	if (!platdata->clock)
-		platdata->clock = dev_read_u32_default(dev, "clock-frequency", 0);
-	if (!platdata->clock) {
-		debug("SiFive UART clock not defined\n");
-		return -EINVAL;
+		ret = dev_read_u32(dev, "clock-frequency", &clock);
+		if (IS_ERR_VALUE(ret)) {
+			debug("SiFive UART clock not defined\n");
+			return 0;
+		}
+	} else {
+		clock = clk_get_rate(&clk);
+		if (IS_ERR_VALUE(clock)) {
+			debug("SiFive UART clock get rate failed\n");
+			return 0;
+		}
 	}
-
+	platdata->clock = clock;
 	_sifive_serial_setbrg(platdata->regs, platdata->clock, baudrate);
 
 	return 0;
@@ -109,7 +135,6 @@ static int sifive_serial_probe(struct udevice *dev)
 	if (gd->flags & GD_FLG_RELOC)
 		return 0;
 
-	platdata->saved_input_char = 0;
 	_sifive_serial_init(platdata->regs);
 
 	return 0;
@@ -121,12 +146,6 @@ static int sifive_serial_getc(struct udevice *dev)
 	struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
 	struct uart_sifive *regs = platdata->regs;
 
-	if (platdata->saved_input_char > 0) {
-		c = platdata->saved_input_char;
-		platdata->saved_input_char = 0;
-		return c;
-	}
-
 	while ((c = _sifive_serial_getc(regs)) == -EAGAIN) ;
 
 	return c;
@@ -147,14 +166,10 @@ static int sifive_serial_pending(struct udevice *dev, bool input)
 	struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
 	struct uart_sifive *regs = platdata->regs;
 
-	if (input) {
-		if (platdata->saved_input_char > 0)
-			return 1;
-		platdata->saved_input_char = _sifive_serial_getc(regs);
-		return (platdata->saved_input_char > 0) ? 1 : 0;
-	} else {
+	if (input)
+		return (readl(&regs->ip) & UART_IP_RXWM);
+	else
 		return !!(readl(&regs->txfifo) & UART_TXFIFO_FULL);
-	}
 }
 
 static int sifive_serial_ofdata_to_platdata(struct udevice *dev)