ARM: OMAP1: create read_reset_sources() function (for initial use by watchdog)

On OMAP1, the existing OMAP watchdog driver reads a register directly
from a non-watchdog IP block.  It also does not convert the register's
contents into the standard WDIOF_* bits expected from the
GETBOOTSTATUS ioctl().

To move towards fixing these problems, create an function in
arch/arm/mach-omap1 to return the reset source data.  A subsequent
patch will provide this function to the watchdog driver via
platform_data.

In the long term, the best approach would be to move this function
to a new OMAP1 driver that handles access to the OMAP1 Clock
Generation and Reset Management IP block.  Then no platform_data would
be needed.
Signed-off-by: Paul Walmsley <paul@pwsan.com>

arch/arm/mach-omap1/common.h

@@ -90,4 +90,6 @@ extern int ocpi_enable(void);
 static inline int ocpi_enable(void) { return 0; }
 #endif
 
+extern int omap1_get_reset_sources(void);
+
 #endif /* __ARCH_ARM_MACH_OMAP1_COMMON_H */

arch/arm/mach-omap1/reset.c

@@ -10,6 +10,19 @@
 
 #include "common.h"
 
+/* ARM_SYSST bit shifts related to SoC reset sources */
+#define ARM_SYSST_POR_SHIFT				5
+#define ARM_SYSST_EXT_RST_SHIFT				4
+#define ARM_SYSST_ARM_WDRST_SHIFT			2
+#define ARM_SYSST_GLOB_SWRST_SHIFT			1
+
+/* Standardized reset source bits (across all OMAP SoCs) */
+#define OMAP_GLOBAL_COLD_RST_SRC_ID_SHIFT		0
+#define OMAP_GLOBAL_WARM_RST_SRC_ID_SHIFT		1
+#define OMAP_MPU_WD_RST_SRC_ID_SHIFT			3
+#define OMAP_EXTWARM_RST_SRC_ID_SHIFT			5
+
+
 void omap1_restart(char mode, const char *cmd)
 {
 	/*
@@ -23,3 +36,28 @@ void omap1_restart(char mode, const char *cmd)
 
 	omap_writew(1, ARM_RSTCT1);
 }
+
+/**
+ * omap1_get_reset_sources - return the source of the SoC's last reset
+ *
+ * Returns bits that represent the last reset source for the SoC.  The
+ * format is standardized across OMAPs for use by the OMAP watchdog.
+ */
+int omap1_get_reset_sources(void)
+{
+	int ret = 0;
+	u16 rs;
+
+	rs = __raw_readw(ARM_SYSST);
+
+	if (rs & (1 << ARM_SYSST_POR_SHIFT))
+		ret |= 1 << OMAP_GLOBAL_COLD_RST_SRC_ID_SHIFT;
+	if (rs & (1 << ARM_SYSST_EXT_RST_SHIFT))
+		ret |= 1 << OMAP_EXTWARM_RST_SRC_ID_SHIFT;
+	if (rs & (1 << ARM_SYSST_ARM_WDRST_SHIFT))
+		ret |= 1 << OMAP_MPU_WD_RST_SRC_ID_SHIFT;
+	if (rs & (1 << ARM_SYSST_GLOB_SWRST_SHIFT))
+		ret |= 1 << OMAP_GLOBAL_WARM_RST_SRC_ID_SHIFT;
+
+	return ret;
+}