Why are the LDOs getting disabled?

Autonomous Machines Jetson & Embedded Systems Jetson TK1
1

In the kernel bootlog I can see this message initially.

[ 0.511302] as3722 4-0040: AS3722 with revision 0x1 found
[ 0.516143] as3722_sd0: 700 <–> 1300 mV at 1000 mV 3500 mA normal standby
[ 0.517233] as3722_sd1: 700 <–> 1350 mV at 1150 mV 2500 mA normal standby
[ 0.517586] as3722_sd2: 1350 mV normal standby
[ 0.517897] as3722-sd3: no parameters
[ 0.518337] as3722_sd4: 1050 mV normal standby
[ 0.518960] as3722_sd5: 1800 mV normal standby
[ 0.519424] as3722_sd6: applied init 1000000uV constraint
[ 0.520011] as3722_sd6: 650 <–> 1200 mV at 1000 mV 3500 mA normal standby
[ 0.520342] as3722_ldo0: 1050 <–> 1225 mV at 1050 mV at 300 mA normal standby
[ 0.520394] as3722_ldo0: supplied by as3722_sd2
[ 0.521830] as3722_ldo1: 1800 mV at 150 mA normal standby
[ 0.522676] as3722_ldo2: 1200 mV at 150 mA normal standby
[ 0.522725] as3722_ldo2: supplied by as3722_sd5
[ 0.523708] as3722_ldo3: 800 mV at 150 mA normal standby
[ 0.524164] as3722_ldo4: 2700 mV at 150 mA normal standby
[ 0.524615] as3722_ldo5: 1200 mV at 150 mA normal standby
[ 0.524665] as3722_ldo5: supplied by as3722_sd5
[ 0.525005] as3722_ldo6: 1800 <–> 3300 mV at 150 mA normal standby
[ 0.525470] as3722_ldo7: 1050 mV at 150 mA normal standby
[ 0.525520] as3722_ldo7: supplied by as3722_sd5
[ 0.526640] as3722_ldo9: 3300 mV at 150 mA normal standby
[ 0.527095] as3722_ldo10: 2700 mV at 150 mA normal standby
[ 0.527575] as3722_ldo11: 1800 mV at 150 mA normal standby

But after a few seconds they get disabled.

[ 5.072489] Disabling clocks left on by bootloader:
[ 5.072492] audio_2x
[ 5.072504] audio
[ 5.072509] audio4
[ 5.072513] audio3
[ 5.072518] audio2
[ 5.072522] audio1
[ 5.072526] audio0
[ 5.072637] hdmi_audio
[ 5.072644] entropy
[ 5.072658] dsi2-fixed
[ 5.072662] dsi1-fixed
[ 5.072689] trace
[ 5.072699] bsev
[ 5.072757] cclk_lp
[ 5.072767] pll_x_out0
[ 5.072771] pll_u_12M
[ 5.072790] pll_m_out1
[ 5.074112] tegra_dvfs: registered vdd_cpu simon notifier
[ 5.074724] Tegra CPU DFLL is initialized with use_dfll = 1
[ 5.074997] CPU rate: 696 MHz
[ 5.077775] cpu_cold cooling device is registered
[ 5.079033] cpu_hot cooling device is registered
[ 5.336140] tegra dvfs: tegra sysfs cap interface is initialized
[ 5.336304] tegra dvfs: tegra sysfs gpu & emc interface is initialized
[ 5.336311] tegra dvfs: registered vdd_gpu simon notifier
[ 5.336703] tegra_actmon.emc: Completed initialization (0)
[ 5.337086] tegra_actmon.avp: Completed initialization (0)
[ 5.337333] tegra_mon.cpu_emc: Completed initialization (0)
[ 5.340246] as3722_ldo11: disabling
[ 5.340425] as3722_ldo10: disabling
[ 5.340586] as3722_ldo9: disabling
[ 5.340747] as3722_ldo7: disabling
[ 5.340907] as3722_ldo5: disabling
[ 5.341066] as3722_ldo4: disabling
[ 5.341256] as3722_ldo1: disabling
[ 5.341423] as3722-sd3: disabling

Is this happening for anybody else? Why does this behavior occur? How do I make sure that all these LDOs stay enabled during boot (or atleast LDO1)? Could somebody explain please.

2

I found a solution to control the LDO using sysfs:

e.g. for as3722_ldo1:

echo enabled > /sys/devices/platform/tegra12-i2c.4/i2c-4/4-0040/as3722-regulator.0/regulator/regulator.9/state

You must be root to do that.
You can identify the regulators using the name file in each folder.

3

Most of those LDOs are associated with camera support so unless camera is being used those will be turned off. SD3 is turned off because it is not needed; the architecture of the AMS PMIC allows two of the DCDCs (SD2 and SD3) to be ganged together to support higher current. When that is done only one controller is needed.

4

Thank you for your replies. The command you mentioned works like a charm mandre.