ARM: 5884/1: arm: Fix DCC console for v7

Without this patch arch/arm/compressed/head.S defaults to generic
DCC code that does not work for v7.

For more information on the v7 DCC, see Cortex-A8 TRM
"12.11.1 Debug communications channel".

To use it with post 2.6.33-rc1 or later, you need to have:

CONFIG_DEBUG_LL=y
ONFIG_DEBUG_ICEDCC=y
CONFIG_EARLY_PRINTK=y

Earlier kernels need commit 93fd03a8c6728b58879f8af20ffd55d9c32a778b
backported.

Tested on omap3430.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 20 insertions, 0 deletions

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index d356af7cef82..4fddc509e78e 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -27,6 +27,14 @@
                 .macro  writeb, ch, rb
                 mcr     p14, 0, \ch, c0, c5, 0
                 .endm
+#elif defined(CONFIG_CPU_V7)
+                .macro  loadsp, rb
+                .endm
+                .macro  writeb, ch, rb
+wait:           mrc     p14, 0, pc, c0, c1, 0
+                bcs     wait
+                mcr     p14, 0, \ch, c0, c5, 0
+                .endm
 #elif defined(CONFIG_CPU_XSCALE)
                 .macro  loadsp, rb
                 .endm
diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
index af6479fae931..56a0d116d271 100644
--- a/arch/arm/boot/compressed/misc.c
+++ b/arch/arm/boot/compressed/misc.c
@@ -53,6 +53,18 @@ static void icedcc_putc(int ch)
 
         asm("mcr p14, 0, %0, c0, c5, 0" : : "r" (ch));
 }
+
+#elif defined(CONFIG_CPU_V7)
+
+static void icedcc_putc(int ch)
+{
+        asm(
+        "wait:  mrc     p14, 0, pc, c0, c1, 0                   \n\
+                bcs     wait                                    \n\
+                mcr     p14, 0, %0, c0, c5, 0                   "
+        : : "r" (ch));
+}
+
 #elif defined(CONFIG_CPU_XSCALE)
 
 static void icedcc_putc(int ch)