console: Add support for the 16550 UART

And rebuild various binaries

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

hello_world/hello_world.hex

@@ -515,79 +515,117 @@ e8010010ebc1fff0
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include/microwatt_soc.h

@@ -79,6 +79,10 @@
 #define UART_REG_TX       0x00
 #define UART_REG_DLL      0x00
 #define UART_REG_IER      0x04
+#define   UART_REG_IER_RDI      0x01
+#define   UART_REG_IER_THRI     0x02
+#define   UART_REG_IER_RLSI     0x04
+#define   UART_REG_IER_MSI      0x08
 #define UART_REG_DLM      0x04
 #define UART_REG_IIR      0x08
 #define UART_REG_FCR      0x08

lib/console.c

@@ -5,22 +5,29 @@
 #include "microwatt_soc.h"
 #include "io.h"
 
-#define UART_FREQ 115200
+#define UART_BAUDS 115200
 
 /*
  * Core UART functions to implement for a port
  */
 
-static uint64_t potato_uart_base;
+bool uart_is_std;
+
+static uint64_t uart_base;
+
+static unsigned long uart_divisor(unsigned long uart_freq, unsigned long bauds)
+{
+	return uart_freq / (bauds * 16);
+}
 
 static uint64_t potato_uart_reg_read(int offset)
 {
-	return readq(potato_uart_base + offset);
+	return readq(uart_base + offset);
 }
 
 static void potato_uart_reg_write(int offset, uint64_t val)
 {
-	writeq(val, potato_uart_base + offset);
+	writeq(val, uart_base + offset);
 }
 
 static int potato_uart_rx_empty(void)
@@ -65,22 +72,13 @@ static void potato_uart_write(char c)
 	potato_uart_reg_write(POTATO_CONSOLE_TX, val);
 }
 
-static unsigned long potato_uart_divisor(unsigned long proc_freq, unsigned long uart_freq)
-{
-	return proc_freq / (uart_freq * 16) - 1;
-}
-
-void potato_uart_init(void)
+static void potato_uart_init(uint64_t uart_freq)
 {
-	uint64_t proc_freq;
-
-	potato_uart_base = UART_BASE;
-	proc_freq = readq(SYSCON_BASE + SYS_REG_CLKINFO) & SYS_REG_CLKINFO_FREQ_MASK;
-
-	potato_uart_reg_write(POTATO_CONSOLE_CLOCK_DIV, potato_uart_divisor(proc_freq, UART_FREQ));
+	unsigned long div = uart_divisor(uart_freq, UART_BAUDS) - 1;
+	potato_uart_reg_write(POTATO_CONSOLE_CLOCK_DIV, div);
 }
 
-void potato_uart_set_irq_en(bool rx_irq, bool tx_irq)
+static void potato_uart_set_irq_en(bool rx_irq, bool tx_irq)
 {
 	uint64_t en = 0;
 
@@ -91,25 +89,76 @@ void potato_uart_set_irq_en(bool rx_irq, bool tx_irq)
 	potato_uart_reg_write(POTATO_CONSOLE_IRQ_EN, en);
 }
 
-void potato_uart_irq_dis(void)
+static bool std_uart_rx_empty(void)
 {
-	potato_uart_reg_write(POTATO_CONSOLE_IRQ_EN, 0x00);
+	return !(readb(uart_base + UART_REG_LSR) & UART_REG_LSR_DR);
 }
 
-int getchar(void)
+static uint8_t std_uart_read(void)
 {
-	while (potato_uart_rx_empty())
-		/* Do nothing */ ;
+	return readb(uart_base + UART_REG_RX);
+}
 
-	return potato_uart_read();
+static bool std_uart_tx_full(void)
+{
+	return !(readb(uart_base + UART_REG_LSR) & UART_REG_LSR_THRE);
 }
 
-int putchar(int c)
+static void std_uart_write(uint8_t c)
 {
-	while (potato_uart_tx_full())
-		/* Do Nothing */;
+	writeb(c, uart_base + UART_REG_TX);
+}
+
+static void std_uart_set_irq_en(bool rx_irq, bool tx_irq)
+{
+	uint8_t ier = 0;
 
-	potato_uart_write(c);
+	if (tx_irq)
+		ier |= UART_REG_IER_THRI;
+	if (rx_irq)
+		ier |= UART_REG_IER_RDI;
+	writeb(ier, uart_base + UART_REG_IER);
+}
+
+static void std_uart_init(uint64_t uart_freq)
+{
+	unsigned long div = uart_divisor(uart_freq, UART_BAUDS);
+	
+	writeb(UART_REG_LCR_DLAB,     uart_base + UART_REG_LCR);
+	writeb(div & 0xff,            uart_base + UART_REG_DLL);
+	writeb(div >> 8,              uart_base + UART_REG_DLM);
+	writeb(UART_REG_LCR_8BIT,     uart_base + UART_REG_LCR);
+	writeb(UART_REG_MCR_DTR |
+	       UART_REG_MCR_RTS,      uart_base + UART_REG_MCR);
+	writeb(UART_REG_FCR_EN_FIFO |
+	       UART_REG_FCR_CLR_RCVR |
+	       UART_REG_FCR_CLR_XMIT, uart_base + UART_REG_FCR);
+}
+
+int getchar(void)
+{
+	if (uart_is_std) {
+		while (std_uart_rx_empty())
+			/* Do nothing */ ;
+		return std_uart_read();
+	} else {
+		while (potato_uart_rx_empty())
+			/* Do nothing */ ;
+		return potato_uart_read();
+	}
+}
+
+int putchar(int c)
+{
+	if (uart_is_std) {
+		while(std_uart_tx_full())
+			/* Do Nothing */;
+		std_uart_write(c);
+	} else {
+		while (potato_uart_tx_full())
+			/* Do Nothing */;
+		potato_uart_write(c);
+	}
 	return c;
 }
 
@@ -140,10 +189,35 @@ size_t strlen(const char *s)
 
 void console_init(void)
 {
-	potato_uart_init();
+	uint64_t sys_info;
+	uint64_t proc_freq;
+	uint64_t uart_info = 0;
+	uint64_t uart_freq = 0;
+
+	proc_freq = readq(SYSCON_BASE + SYS_REG_CLKINFO) & SYS_REG_CLKINFO_FREQ_MASK;
+	sys_info  = readq(SYSCON_BASE + SYS_REG_INFO);
+
+	if (sys_info & SYS_REG_INFO_HAS_LARGE_SYSCON) {
+		uart_info = readq(SYSCON_BASE + SYS_REG_UART0_INFO);
+		uart_freq = uart_info & 0xffffffff;
+	}
+	if (uart_freq == 0)
+		uart_freq = proc_freq;
+
+	uart_base = UART_BASE;
+	if (uart_info & SYS_REG_UART_IS_16550) {
+		uart_is_std = true;
+		std_uart_init(proc_freq);
+	} else {
+		uart_is_std = false;
+		potato_uart_init(proc_freq);
+	}
 }
 
 void console_set_irq_en(bool rx_irq, bool tx_irq)
 {
-	potato_uart_set_irq_en(rx_irq, tx_irq);
+	if (uart_is_std)
+		std_uart_set_irq_en(rx_irq, tx_irq);
+	else
+		potato_uart_set_irq_en(rx_irq, tx_irq);
 }