AM6442: Temperature Setting of Refresh rate of LPDDR4/DDR4 by DDR Subsystem Register Configuration tool (0.09.10) Web version

Hi Hideaki-san,

I have assigned the query to the subject matter expert. Please expect delayed response as the expert is currently out of office & will return next week.

Thanks for your patience.

Regards,

Prashant

Hi Hideaki-san,

for DDR4, you have to manually change the tREFI value to half (3900ns) when choosing a temp range that is higher than 85C.  Note that tRFC does not change based on temperature.  tRFC should remain the same.  This is most likely why they are seeing boot up issues

There are several changes to the config file when changing the temp range.  You can see these differences as you make changes if you open one of the files on the right side of the configuration tool

Regards,

James

Hi James,

Thank you so much for your answers.

Could you please tell them how to set the fixed rate for two cases: tREFI = 3.9us and 1.95us ?  The manual changing is no problem.

In their application, TCR mode should be disabled and a fixed refresh interval should be used to avoid performance variations due to temperature.

For DDR4, if they set 95degC by using the tool, the following register setting values ​​will be output, and the refresh interval will be set the automatic adjust.

e.g. #define DDRSS_CTL_230_DATA 0x0000000C

MR4[3] =  1 : TCR mode enable

MR4[2] = 1 : Extended Temperature Mode

Thanks and regards,

Hideaki

Hideaki, first, they should be using the latest tool 0.10.01 found at https://dev.ti.com/sysconfig/?product=Processor_DDR_Config&device=AM64x

Currently in the tool, the temp controlled refresh is turned on automatically if a temp is chosen above 85C.  If they want to disable that, they would have to hand modify the following registers

CTL_230 thru CTL 235

PI_301, PI_309, PI_317, PI_325, PI_333, PI_341

back to a value of 0x0.

I will add this as a selectable option in the next version of the tool.  

Regards,

James

Hi James,

Thank you for your answers. The customer tried the latest tool, but not yet solved this issue. Please answer their questions below.

1)  They tried the latest tool, but tREFI=7800 remained. Is it correct way to change it to 3900 on the tool manually in order to set the fixed refresh rate ?

2)  In the method you taught, MR2[7:6]=11b ASR mode, is the normal Refresh only fixed setting, and auto self refresh is automatic setting?

        Low-power auto self refresh (LPASR) – Mode summary

        00 = Manual mode - Normal operating temperature range (TC: –40°C–85°C)

        01 = Manual mode - Reduced operating temperature range (TC: –40°C–45°C)

        10 = Manual mode - Extended operating temperature range (TC: –40°C–125°C)

        11 = ASR mode - Automatically switching among all modes

3)  Which register and what value should be set manually to fix LPASR to Manual mode Extended operation temp. Range?

4)  When does Low-power auto self refresh (LPASR) occur ?
When Linux is running normally, will the status change automatically if the operation is intermittent? Or will this mechanism work only in special cases? For example, suspend.

Thanks and regards,

Hideaki

Hideaki-san,

1. Yes, refresh rate should be changed manually in the tool as needed

2. The tool will choose 00b Manual mode normal for 40-85C, and 11b ASR modes for all other operating temp ranges.  

3. To choose Manual mode - Extended, the customer would need to change the registers i mentioned above.  the MR2 parameter is in the LSBs of the register, so to change to Extended, change bits 7:6 = 10b in each of the registers.  Can you explain why the customer is wanting to choose this?  It seems ASR mode is more optimized.  If it is commonly needed, i can add it as an option in the sysconfig tool

4. The auto self refresh will occur when the processor is placed into a low power mode (see https://software-dl.ti.com/processor-sdk-linux/esd/AM62AX/09_01_00/exports/docs/linux/Foundational_Components_Kernel_Drivers_Power_Management.html)  Currently the SDKs do not support automatic self refresh, whereby the memory is put into self refresh mode during idle periods.

Regards,

James