[PATCH] arm64: add support for uart earlyprintk

[apatel@apm.com (Anup Patel)]

Signed-off-by: Anup Patel <apatel@apm.com>
---
 arch/arm64/kernel/early_printk.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c
index 7e320a2..62953ed 100644
--- a/arch/arm64/kernel/early_printk.c
+++ b/arch/arm64/kernel/early_printk.c
@@ -29,6 +29,21 @@ static void __iomem *early_base;
 static void (*printch)(char ch);
 
 /*
+ * UART (8250/16550) single character TX.
+ */
+static void uart_printch(char ch)
+{
+#define UART_LSR 	0x14
+#define UART_TX 	0x0
+
+	while (!(readl_relaxed(early_base + UART_LSR) & 0x20))
+		;
+	writeb_relaxed(ch, early_base + UART_TX);
+	while (!(readl_relaxed(early_base + UART_LSR) & 0x20))
+		;
+}
+
+/*
  * PL011 single character TX.
  */
 static void pl011_printch(char ch)
@@ -47,6 +62,7 @@ struct earlycon_match {
 
 static const struct earlycon_match earlycon_match[] __initconst = {
 	{ .name = "pl011", .printch = pl011_printch, },
+	{ .name = "uart", .printch = uart_printch, },
 	{}
 };
 
-- 
1.7.9.5

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