Initial commit: OpenHarmony-v4.0-ReleaseOpenHarmony-v4.0-Release

1 files changed, 54 insertions, 0 deletions

diff --git a/arch/mips/kernel/early_printk_8250.c b/arch/mips/kernel/early_printk_8250.c
new file mode 100644
index 000000000..567c6ec0c
--- /dev/null
+++ b/arch/mips/kernel/early_printk_8250.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  8250/16550-type serial ports prom_putchar()
+ *
+ *  Copyright (C) 2010  Yoichi Yuasa <yuasa@linux-mips.org>
+ */
+#include <linux/io.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <asm/setup.h>
+
+static void __iomem *serial8250_base;
+static unsigned int serial8250_reg_shift;
+static unsigned int serial8250_tx_timeout;
+
+void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift,
+                                  unsigned int timeout)
+{
+        serial8250_base = (void __iomem *)base;
+        serial8250_reg_shift = reg_shift;
+        serial8250_tx_timeout = timeout;
+}
+
+static inline u8 serial_in(int offset)
+{
+        return readb(serial8250_base + (offset << serial8250_reg_shift));
+}
+
+static inline void serial_out(int offset, char value)
+{
+        writeb(value, serial8250_base + (offset << serial8250_reg_shift));
+}
+
+void prom_putchar(char c)
+{
+        unsigned int timeout;
+        int status, bits;
+
+        if (!serial8250_base)
+                return;
+
+        timeout = serial8250_tx_timeout;
+        bits = UART_LSR_TEMT | UART_LSR_THRE;
+
+        do {
+                status = serial_in(UART_LSR);
+
+                if (--timeout == 0)
+                        break;
+        } while ((status & bits) != bits);
+
+        if (timeout)
+                serial_out(UART_TX, c);
+}