ARM: dts: am335x-boneblack: disable RTC-only sleep to avoid hardware damage

Avoid entering "RTC-only mode" at poweroff. It is unsupported by most
versions of BeagleBone, and risks hardware damage.

The damaging configuration is having system-power-controller
without ti,pmic-shutdown-controller.

Reported-by: Matthijs van Duin <matthijsvanduin@gmail.com>
Tested-by: Matthijs van Duin <matthijsvanduin@gmail.com>
Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Johan Hovold <johan@kernel.org>
[Matthijs van Duin: added explanatory comments]
Signed-off-by: Matthijs van Duin <matthijsvanduin@gmail.com>
Fixes: http://bugs.elinux.org/issues/143
Cc: stable@vger.kernel.org # v3.12+
[tony@atomide.com: updated comments with the hardware breaking info]
Signed-off-by: Tony Lindgren <tony@atomide.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/arm/boot/dts/am335x-bone-common.dtsi b/arch/arm/boot/dts/am335x-bone-common.dtsi
index c3255e0c90aa..dbb3f4d2bf84 100644
--- a/arch/arm/boot/dts/am335x-bone-common.dtsi
+++ b/arch/arm/boot/dts/am335x-bone-common.dtsi
@@ -223,6 +223,25 @@
 /include/ "tps65217.dtsi"
 
 &tps {
+        /*
+         * Configure pmic to enter OFF-state instead of SLEEP-state ("RTC-only
+         * mode") at poweroff.  Most BeagleBone versions do not support RTC-only
+         * mode and risk hardware damage if this mode is entered.
+         *
+         * For details, see linux-omap mailing list May 2015 thread
+         *      [PATCH] ARM: dts: am335x-bone* enable pmic-shutdown-controller
+         * In particular, messages:
+         *      http://www.spinics.net/lists/linux-omap/msg118585.html
+         *      http://www.spinics.net/lists/linux-omap/msg118615.html
+         *
+         * You can override this later with
+         *      &tps {  /delete-property/ ti,pmic-shutdown-controller;  }
+         * if you want to use RTC-only mode and made sure you are not affected
+         * by the hardware problems. (Tip: double-check by performing a current
+         * measurement after shutdown: it should be less than 1 mA.)
+         */
+        ti,pmic-shutdown-controller;
+
         regulators {
                 dcdc1_reg: regulator@0 {
                         regulator-name = "vdds_dpr";