RTC IP have kicker feature which prevents spurious writes to its registers.
In order to write into any of the RTC registers, KICK values has to be
written to KICK registers. Also, RTC busy flag needs to be polled for
non-TC registers as well, without which update is not proper and confirmed
it by testing on DRA7-evm.
Introduce omap_hwmod_rtc_unlock/lock functions, which writes into these
KICK registers inorder to lock and unlock RTC registers.
Signed-off-by: Lokesh Vutla <lokeshvutla@xxxxxx>
---
Changes since v5:
- Updated commit message and fixed a comment.
arch/arm/mach-omap2/omap_hwmod.h | 2 ++
arch/arm/mach-omap2/omap_hwmod_reset.c | 65 ++++++++++++++++++++++++++++++++++
2 files changed, 67 insertions(+)
diff --git a/arch/arm/mach-omap2/omap_hwmod.h b/arch/arm/mach-omap2/omap_hwmod.h
index 76bce11..649576e 100644
--- a/arch/arm/mach-omap2/omap_hwmod.h
+++ b/arch/arm/mach-omap2/omap_hwmod.h
@@ -751,6 +751,8 @@ const char *omap_hwmod_get_main_clk(struct omap_hwmod *oh);
*/
extern int omap_hwmod_aess_preprogram(struct omap_hwmod *oh);
+void omap_hwmod_rtc_unlock(struct omap_hwmod *oh);
+void omap_hwmod_rtc_lock(struct omap_hwmod *oh);
/*
* Chip variant-specific hwmod init routines - XXX should be converted
diff --git a/arch/arm/mach-omap2/omap_hwmod_reset.c b/arch/arm/mach-omap2/omap_hwmod_reset.c
index 65e186c..409bda3 100644
--- a/arch/arm/mach-omap2/omap_hwmod_reset.c
+++ b/arch/arm/mach-omap2/omap_hwmod_reset.c
@@ -29,6 +29,16 @@
#include <sound/aess.h>
#include "omap_hwmod.h"
+#include "common.h"
+
+#define OMAP_RTC_STATUS_REG 0x44
+#define OMAP_RTC_KICK0_REG 0x6c
+#define OMAP_RTC_KICK1_REG 0x70
+
+#define OMAP_RTC_KICK0_VALUE 0x83E70B13
+#define OMAP_RTC_KICK1_VALUE 0x95A4F1E0
+#define OMAP_RTC_STATUS_BUSY BIT(0)
+#define OMAP_RTC_MAX_READY_TIME 50
/**
* omap_hwmod_aess_preprogram - enable AESS internal autogating
@@ -51,3 +61,58 @@ int omap_hwmod_aess_preprogram(struct omap_hwmod *oh)
return 0;
}
+
+/**
+ * omap_rtc_wait_not_busy - Wait for the RTC BUSY flag
+ * @oh: struct omap_hwmod *
+ *
+ * For updating certain RTC registers, the MPU must wait
+ * for the BUSY status in OMAP_RTC_STATUS_REG to become zero.
+ * Once the BUSY status is zero, there is a 15 microseconds access
+ * period in which the MPU can program.
+ */
+static void omap_rtc_wait_not_busy(struct omap_hwmod *oh)
+{
+ int i;
+
+ /* BUSY may stay active for 1/32768 second (~30 usec) */
+ omap_test_timeout(omap_hwmod_read(oh, OMAP_RTC_STATUS_REG)
+ & OMAP_RTC_STATUS_BUSY, OMAP_RTC_MAX_READY_TIME, i);
+ /* now we have ~15 microseconds to read/write various registers */
+}
+
+/**
+ * omap_hwmod_rtc_unlock - Unlock the Kicker mechanism.
+ * @oh: struct omap_hwmod *
+ *
+ * RTC IP have kicker feature. This prevents spurious writes to its registers.
+ * In order to write into any of the RTC registers, KICK values has te be
+ * written in respective KICK registers. This is needed for hwmod to write into
+ * sysconfig register.
+ */
+void omap_hwmod_rtc_unlock(struct omap_hwmod *oh)
+{
+ local_irq_disable();
+ omap_rtc_wait_not_busy(oh);
+ omap_hwmod_write(OMAP_RTC_KICK0_VALUE, oh, OMAP_RTC_KICK0_REG);
+ omap_hwmod_write(OMAP_RTC_KICK1_VALUE, oh, OMAP_RTC_KICK1_REG);
+ local_irq_enable();
+}
+
+/**
+ * omap_hwmod_rtc_lock - Lock the Kicker mechanism.
+ * @oh: struct omap_hwmod *
+ *
+ * RTC IP have kicker feature. This prevents spurious writes to its registers.
+ * Once the RTC registers are written, KICK mechanism needs to be locked,
+ * in order to prevent any spurious writes. This function locks back the RTC
+ * registers once hwmod completes its write into sysconfig register.
+ */
+void omap_hwmod_rtc_lock(struct omap_hwmod *oh)
+{
+ local_irq_disable();
+ omap_rtc_wait_not_busy(oh);
+ omap_hwmod_write(0x0, oh, OMAP_RTC_KICK0_REG);
+ omap_hwmod_write(0x0, oh, OMAP_RTC_KICK1_REG);
+ local_irq_enable();
+}
--
2.1.4
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