ARM: OMAP2+: hwmod: RTC: Add lock and unlock hooks

This series implements lock and unlock functions for RTC and hooks the same to DRA7 and AMx3xx hwmod.
This is dependent on the patch https://patchwork.kernel.org/patch/6578281/,
which is queued recently by Paul.

Changes since v2:
- Add kerneldoc for omap_hwmod_rtc_lock() function.

Lokesh Vutla (3):
ARM: hwmod: RTC: Add lock and unlock functions
ARM: DRA7: RTC: Add lock and unlock functions
ARM: AMx3xx: RTC: Add lock and unlock functions

 arch/arm/mach-omap2/omap_hwmod.h                   |  2 +
 .../mach-omap2/omap_hwmod_33xx_43xx_ipblock_data.c |  2 +
 arch/arm/mach-omap2/omap_hwmod_7xx_data.c          |  2 +
 arch/arm/mach-omap2/omap_hwmod_reset.c             | 65 ++++++++++++++++++++++
 4 files changed, 71 insertions(+)

2.1.4

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.
Introduce omap_hwmod_rtc_unlock/lock functions, which writes into these KICK registers inorder to lock and unlock RTC registers.

---
 arch/arm/mach-omap2/omap_hwmod.h       |  2 ++
 arch/arm/mach-omap2/omap_hwmod_reset.c | 65 ++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)

index c697b57..173a31e 100644
@@ -748,6 +748,8 @@ 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

2.1.4

Hook omap_hwmod_rtc_unlock/lock functions into RTC hwmod, so that SYSCONFIG register is updated properly

---
 arch/arm/mach-omap2/omap_hwmod_7xx_data.c | 2 ++
 1 file changed, 2 insertions(+)

index 2606c66..95d9bc5c 100644
@@ -1572,6 +1572,8 @@ static struct omap_hwmod_class_sysconfig dra7xx_rtcss_sysc = {
 static struct omap_hwmod_class dra7xx_rtcss_hwmod_class = {
 	.name	= "rtcss",
 	.sysc	= &dra7xx_rtcss_sysc,
+	.unlock	= &omap_hwmod_rtc_unlock,
+	.lock	= &omap_hwmod_rtc_lock,
 };
 
 /* rtcss */

2.1.4

Hook omap_hwmod_rtc_unlock/lock functions into RTC hwmod, so that SYSCONFIG register is updated properly.

---
 arch/arm/mach-omap2/omap_hwmod_33xx_43xx_ipblock_data.c | 2 ++
 1 file changed, 2 insertions(+)

index 907a452b..aed3362 100644
@@ -918,6 +918,8 @@ static struct omap_hwmod_class_sysconfig am33xx_rtc_sysc = {
 static struct omap_hwmod_class am33xx_rtc_hwmod_class = {
 	.name		= "rtc",
 	.sysc		= &am33xx_rtc_sysc,
+	.unlock		= &omap_hwmod_rtc_unlock,
+	.lock		= &omap_hwmod_rtc_lock,
 };
 
 struct omap_hwmod am33xx_rtc_hwmod = {

2.1.4

Hi Paul,

Gentle ping on this series.

Thanks and regards,
Lokesh

Hi Paul,

Do you have any comments on this series?

Thanks and regards,
Lokesh

Looks pretty good. I'm slightly concerned about the latency jitter impact on -rt kernels for that local_irq_disable() section. Looks like it could hold off interrupts for ~(50 udelay ?s) + 50*((RTC register read time) + 1). But I'm not sure if preempt_enable/disable() is a good alternative since a bunch of interrupt top halves could conceivably run after the RTC goes non-busy and result in the RTC not being locked/unlocked.

Is there an RTC IP block register that the code can read, or a safe sequence that the code can execute, after the RTC lock/unlock operation to verify that the RTC has successfully been locked or unlocked? If so then it's probably worth converting the local_irq_disable/enable() to preempt_disable/enable() and testing that, then retrying the lock/unlock if it fails.

- Paul

Hi Paul,

Agree.

I am afraid there is no such register to verify lock or unlock. Also these KICK registers are Write only registers so can't read back the value. Even the driver implement the same api's for writing into registers.

One thing I can think of is that to write a known pattern to scratch pad register and read back the value to confirm if it is locked/unlocked. But don't think this is a good approach.

Thanks and regards,
Lokesh