[ARM] 4412/1: S3C2412: reset errata fix

The S3C2412 has an reset-errata where the clock
may cause a glitch switching back to EXTCLK. We
force a switch to EXTCLK before writing the
reset register to force use of the CLKCON sync
logic to properly switch.

Fix problem reported by Matthieu Castet.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/arm/mach-s3c2412/s3c2412.c b/arch/arm/mach-s3c2412/s3c2412.c
index c602aa39f9c4..782b5814ced2 100644
--- a/arch/arm/mach-s3c2412/s3c2412.c
+++ b/arch/arm/mach-s3c2412/s3c2412.c
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/timer.h>
 #include <linux/init.h>
+#include <linux/delay.h>
 #include <linux/sysdev.h>
 #include <linux/serial_core.h>
 #include <linux/platform_device.h>
@@ -29,6 +30,7 @@
 #include <asm/io.h>
 #include <asm/irq.h>
 
+#include <asm/arch/reset.h>
 #include <asm/arch/idle.h>
 
 #include <asm/arch/regs-clock.h>
@@ -38,6 +40,7 @@
 #include <asm/arch/regs-gpioj.h>
 #include <asm/arch/regs-dsc.h>
 #include <asm/arch/regs-spi.h>
+#include <asm/arch/regs-s3c2412.h>
 
 #include <asm/plat-s3c24xx/s3c2412.h>
 #include <asm/plat-s3c24xx/cpu.h>
@@ -106,6 +109,23 @@ static void s3c2412_idle(void)
         cpu_do_idle();
 }
 
+static void s3c2412_hard_reset(void)
+{
+        /* errata "Watch-dog/Software Reset Problem" specifies that
+         * this reset must be done with the SYSCLK sourced from
+         * EXTCLK instead of FOUT to avoid a glitch in the reset
+         * mechanism.
+         *
+         * See the watchdog section of the S3C2412 manual for more
+         * information on this fix.
+         */
+
+        __raw_writel(0x00, S3C2412_CLKSRC);
+        __raw_writel(S3C2412_SWRST_RESET, S3C2412_SWRST);
+
+        mdelay(1);
+}
+
 /* s3c2412_map_io
  *
  * register the standard cpu IO areas, and any passed in from the
@@ -122,6 +142,10 @@ void __init s3c2412_map_io(struct map_desc *mach_desc, int mach_size)
 
         s3c24xx_idle = s3c2412_idle;
 
+        /* set custom reset hook */
+
+        s3c24xx_reset_hook = s3c2412_hard_reset;
+
         /* register our io-tables */
 
         iotable_init(s3c2412_iodesc, ARRAY_SIZE(s3c2412_iodesc));