From: Marc Zyngier <Marc.Zyngier@arm.com>
Date: Wed, 27 Feb 2013 18:06:00 +0000 (+0000)
Subject: arm64: early_printk: add support for FastModel console output
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=0492f72508184d451101564e235b0c32edf9acd3;p=linux-beck.git

arm64: early_printk: add support for FastModel console output

Enable early_printk to use the FastModel semihosting to output
the early kernel messages. Works both for host and guest kernels.

To use this feature, pass "early_printk=smh" to the kernel.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c
index 7e320a2edb9b..0bb7436c57dc 100644
--- a/arch/arm64/kernel/early_printk.c
+++ b/arch/arm64/kernel/early_printk.c
@@ -40,6 +40,17 @@ static void pl011_printch(char ch)
 		;
 }
 
+/*
+ * Semihosting-based debug console
+ */
+static void smh_printch(char ch)
+{
+	asm volatile("mov  x1, %0\n"
+		     "mov  x0, #3\n"
+		     "hlt  0xf000\n"
+		     : : "r" (&ch) : "x0", "x1", "memory");
+}
+
 struct earlycon_match {
 	const char *name;
 	void (*printch)(char ch);
@@ -47,6 +58,7 @@ struct earlycon_match {
 
 static const struct earlycon_match earlycon_match[] __initconst = {
 	{ .name = "pl011", .printch = pl011_printch, },
+	{ .name = "smh", .printch = smh_printch, },
 	{}
 };