[PATCH v2 0/5] ARM: at91: fix hanged boot

Johan Hovold jhovold at gmail.com
Mon Mar 11 14:07:54 EDT 2013

These patches fix a few severe issues affecting most AT91 SOCs where
boot can hang after a non-general reset, and where the only way to get
the system booting again is to do a general reset -- something which
could require physically removing any backup battery.

The problems stem from the fact that the RTC and RTT-peripherals are
powered by backup power (VDDBU) and are not reset on wake-up, user,
watchdog or software reset. Consequently, RTC and RTT-alarms and their
interrupts may be enabled at boot, leading to a system lock-up when an
interrupt arrives on the shared system-interrupt line before the
appropriate handler (e.g. RTC-driver) has been installed.

The easiest way to trigger this is to simply wake up from an RTC-alarm
on at91sam9g45. The RTC-driver currently does not disable interrupts at
shutdown so even after a clean shut-down the system will always hang
after waking up.

The first patch fixes this very general case of RTC-wake up after a
clean shutdown in the RTC-driver and is marked for stable as it is
perfectly straight-forward. [ Note that the other, RTT-based, AT91
RTC-driver already disables its interrupts at shutdown. ]

The more general problem can be triggered, for example, by doing a
user-reset while updating the RTC-time or if an RTC or RTT-alarm goes
off after a non-clean shutdown.

To fix this I propose that arch-code should mask the relevant interrupts
before enabling the system interrupt at early boot, and this is what
the fifth patch does. To access the RTC-registers I choose to revert a
recent patch that moved the register definitions to drivers/rtc.

Arguably, the relevant interrupts could also be disabled in bootloaders,
but I suggest fixing it in the kernel once and for all.

The patches have been tested on at91sam9263 and at91sam9g45 (non-DT),
and compile-tested for the other SOCs and DT.


 - add DT-support
 - make sys_irq_mask non-mandatory

Johan Hovold (5):
  ARM: at91/rtc: fix boot after RTC wake-up
  ARM: at91/dts: add RTC nodes
  ARM: at91/dts: add RTT nodes
  Revert "arm: at91: move at91rm9200 rtc header in drivers/rtc"
  ARM: at91: fix hanged boot

 arch/arm/boot/dts/at91rm9200.dtsi          |  5 ++
 arch/arm/boot/dts/at91sam9260.dtsi         |  5 ++
 arch/arm/boot/dts/at91sam9263.dtsi         | 10 ++++
 arch/arm/boot/dts/at91sam9g45.dtsi         | 10 ++++
 arch/arm/boot/dts/at91sam9n12.dtsi         |  5 ++
 arch/arm/boot/dts/at91sam9x5.dtsi          |  5 ++
 arch/arm/mach-at91/at91sam9260.c           |  6 ++
 arch/arm/mach-at91/at91sam9261.c           |  6 ++
 arch/arm/mach-at91/at91sam9263.c           |  7 +++
 arch/arm/mach-at91/at91sam9g45.c           |  7 +++
 arch/arm/mach-at91/at91sam9rl.c            |  7 +++
 arch/arm/mach-at91/generic.h               |  2 +
 arch/arm/mach-at91/include/mach/at91_rtc.h | 75 +++++++++++++++++++++++++
 arch/arm/mach-at91/setup.c                 | 88 ++++++++++++++++++++++++++++++
 arch/arm/mach-at91/soc.h                   |  1 +
 drivers/rtc/rtc-at91rm9200.c               | 11 +++-
 drivers/rtc/rtc-at91rm9200.h               | 75 -------------------------
 17 files changed, 249 insertions(+), 76 deletions(-)
 create mode 100644 arch/arm/mach-at91/include/mach/at91_rtc.h
 delete mode 100644 drivers/rtc/rtc-at91rm9200.h


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