IMX28 board Current issue( after mem mode case )

[sung-ukjang]

Dear Freescale.

I have question IMX28 Board current issue after mem mode.

We are testing to standby mode and mem mode on IMX28 board.

In cpu clock 454MHz case, idle status board current is 86mA.

But , Entry to mem mode and after wake up board, board current is 94mA.( more up to 10%)

i want know Why that increase power current??

what is difference befor mem mode and after mem mode?

customer project is mobile phone application., so power consumption is very important.

please help us.

thanks.

[Yuri]

The i.MX28 BSP supports CPUFREQ feature. Please check what configuration was actual before entering the mem-mode
and after wakeup.

# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

[sung-ukjang]

Hi Freescale

Current CPU clock value is same 454.736(454.736MHz) - befor and after mem mode.

Customer is had some point jumper on IMX28EVK, so we successed test mem mode.

please check to this current issue.

thanks

[igorpadykov]

Hi Sung-Uk,

just small remark below: :smileyhappy:

so called "mem mode" is not real low power mode, because

really i.MX28 is completely powered down, while state of its main

modules [really not all], CLKCTRL, PinCtrl are saved in DDR memory

[so called "context"]. From sect.3.6.2 "Suspend-To-RAM mode "

AN4199 Using the i.MX28 Power Management Unit and Battery Charger:

"In this mode, the i.MX28 is placed in the Power-Off state. The DRAM is placed in the Self-Refresh state,

and all the context and register values are stored in the DRAM to allow the device to wake up quickly on

resume. As the i.MX28 is in Power-Off state, the DC-DC converter is not active. Therefore, an external

power supply is needed for the DRAM. Only PSWITCH can be used to wake up the device from

Suspend-To-RAM mode."

Practical consequence from this solution is next: for example some device is

active after OS start-up. Then your application wisely decided to turn it off just before 

entering "mem mode". However after exit from "mem mode" you will see that it is still

active and current is more, then just before entering "mem mode". This happened because

you should save in "context" state of this device. Exit from "mem mode" is cold start-up

event with restoring only data, which one saved in "context".

So suggestion to check what is saved in your "context", this depends on particular

application.

Best regards

chip

[igorpadykov]

Hi

please try

echo standby > /sys/power/state

actually I so not see problem in 10% change, since this

easily may be caused by temperature variations.

[sung-ukjang]

Hi,

Power status value is  

Mem mode @2~3mA , and  Standby mode @ 7mA.

Thanks..

[linsonlinson]

hi，Sung-UK

     sorry to interrupt you

     I have a mem-mode problem ------ suspend to ram wakeup fail

     could you send me informations about how to do mem-mode test （ configure，build 、test）

     85510165@qq.com

     please help me out

[igorpadykov]

Briefly:

in "mem mode" you take responsibility

in software to restore processor state to original

(before entering "mem mode") - only in this case

you will get the same power figures (before and after "mem mode").

[igorpadykov]

Hi Sung-Uk

I believe some peripherals connected to processor

may cause such consumption.

Please try to measure i.MX28 currents,

for example on i.MX28 EVK with Freescale Linux BSP:

echo standby > /sys/power/state

VDDD  10mA

VDDIO 15mA

VDDA   5mA

Also it may be recommended to try measurements with board

without populated external components.

Best regards

chip

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[sung-ukjang]

Dear Freescale.

I had check Current status.

Why difference before and after current status??

Just have entry mem-mode and wake up.

Please help.

[igorpadykov]

Hi Sung-Uk

please try measurements with board

without populated external components.

Best regards

chip

[sung-ukjang]

Hi Freescale

My measurements data is only IMX28EVM board test.

[igorpadykov]

Hi Sung-Uk

sorry what do you mean by "mem mode" ?

In the original EVK design (i.MX28 EVK), DRAM power source is provided by the

on-chip power supply and it will be turned off during mem mode.

In order to support suspend to RAM, it must be connected to a constantly

on power source rather than the on-chip power supply.

So "mem mode" can not be tested on i.MX28 EVK.

Probably " IMX28EVM board" as you calls it - something else, not i.MX28 EVK.

So suggestion - please try measurements with board

without populated external components.

Best regards

chip