microblaze: Support early console on uart16550
Early console support reuse setting from U-BOOT that's why
it is not necessary to setup baudrates, etc.
Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/microblaze/kernel/early_printk.c b/arch/microblaze/kernel/early_printk.c
index 685a64e..c3616a0 100644
--- a/arch/microblaze/kernel/early_printk.c
+++ b/arch/microblaze/kernel/early_printk.c
@@ -65,6 +65,50 @@
};
#endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+static void early_printk_uart16550_putc(char c)
+{
+ /*
+ * Limit how many times we'll spin waiting for TX FIFO status.
+ * This will prevent lockups if the base address is incorrectly
+ * set, or any other issue on the UARTLITE.
+ * This limit is pretty arbitrary, unless we are at about 10 baud
+ * we'll never timeout on a working UART.
+ */
+
+ #define UART_LSR_TEMT 0x40 /* Transmitter empty */
+ #define UART_LSR_THRE 0x20 /* Transmit-hold-register empty */
+ #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
+
+ unsigned retries = 10000;
+
+ while (--retries &&
+ !((in_be32(base_addr + 0x14) & BOTH_EMPTY) == BOTH_EMPTY))
+ ;
+
+ if (retries)
+ out_be32(base_addr, c & 0xff);
+}
+
+static void early_printk_uart16550_write(struct console *unused,
+ const char *s, unsigned n)
+{
+ while (*s && n-- > 0) {
+ early_printk_uart16550_putc(*s);
+ if (*s == '\n')
+ early_printk_uart16550_putc('\r');
+ s++;
+ }
+}
+
+static struct console early_serial_uart16550_console = {
+ .name = "earlyser",
+ .write = early_printk_uart16550_write,
+ .flags = CON_PRINTBUFFER,
+ .index = -1,
+};
+#endif /* CONFIG_SERIAL_8250_CONSOLE */
+
static struct console *early_console;
void early_printk(const char *fmt, ...)
@@ -103,6 +147,25 @@
}
#endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
+#ifdef CONFIG_SERIAL_8250_CONSOLE
+ base_addr = early_uart16550_console();
+ base_addr &= ~3; /* clear register offset */
+ if (base_addr) {
+ early_console_initialized = 1;
+#ifdef CONFIG_MMU
+ early_console_reg_tlb_alloc(base_addr);
+#endif
+ early_console = &early_serial_uart16550_console;
+
+ early_printk("early_printk_console is enabled at 0x%08x\n",
+ base_addr);
+
+ /* register_console(early_console); */
+
+ return 0;
+ }
+#endif /* CONFIG_SERIAL_8250_CONSOLE */
+
return 1;
}