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arm64: early_printk: add support for FastModel console output

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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>
This commit is contained in:
Marc Zyngier 2013-02-27 18:06:00 +00:00 • committed by Catalin Marinas
parent d9c1951f40
commit 0492f72508
1 changed files with 12 additions and 0 deletions
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12
arch/arm64/kernel/early_printk.c
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@ -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 { struct earlycon_match {
const char *name; const char *name;
void (*printch)(char ch); void (*printch)(char ch);
@ -47,6 +58,7 @@ struct earlycon_match {
static const struct earlycon_match earlycon_match[] __initconst = { static const struct earlycon_match earlycon_match[] __initconst = {
{ .name = "pl011", .printch = pl011_printch, }, { .name = "pl011", .printch = pl011_printch, },
{ .name = "smh", .printch = smh_printch, },
{} {}
}; };