x86, earlyprintk: Add earlyprintk for Intel Moorestown platform

Intel Moorestown platform has a spi-uart device(Maxim3110),
which connects to a Designware spi core controller. This patch
will add early console function based on it.

As it will be used long before Linux spi subsystem get
initialised, we simply directly manipulate the spi controller's
register to acheive the early console func. This is safe as it
will be disabled when devices subsytem get initialised.

To use it, user need enable CONFIG_X86_MRST_EARLY_PRINTK in
kenrel config and add "earlyprintk=mrst" in kernel command line.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Cc: greg@kroah.com
LKML-Reference: <1284361736-23011-4-git-send-email-feng.tang@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index fa99bae75ace..6082463768a2 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -14,6 +14,7 @@
 #include <xen/hvc-console.h>
 #include <asm/pci-direct.h>
 #include <asm/fixmap.h>
+#include <asm/mrst.h>
 #include <asm/pgtable.h>
 #include <linux/usb/ehci_def.h>
 
@@ -239,6 +240,12 @@ static int __init setup_early_printk(char *buf)
                 if (!strncmp(buf, "xen", 3))
                         early_console_register(&xenboot_console, keep);
 #endif
+#ifdef CONFIG_X86_MRST_EARLY_PRINTK
+                if (!strncmp(buf, "mrst", 4)) {
+                        mrst_early_console_init();
+                        early_console_register(&early_mrst_console, keep);
+                }
+#endif
                 buf++;
         }
         return 0;