topic Re: LPDDR4 Temperature Sensor in i.MX Processors

LPDDR4 Temperature Sensor

philippe_schenk — Tue, 02 Feb 2021 11:47:10 GMT

Hello,

I saw that it is possible to read out the temperature from the LPDDR4 RAM through MR4.

I would like to know if it is possible to read the LPDDR4 RAM temperature in Linux?

I couldn't find any hint in the SCFW porting kit about that it is possible to read that temperature back. Plus the DRC temperature already present in /sys/class/temperature I assume is only the RAM-Controller temperature sitting in the SoC, right?

Thanks for your answer
Philippe Schenker

Re: LPDDR4 Temperature Sensor

jimmychan — Thu, 04 Feb 2021 05:24:37 GMT

Could you tell me which processor are you using?

Which board and which version of BSP are you using?

Re: LPDDR4 Temperature Sensor

philippe_schenk — Tue, 09 Feb 2021 10:46:37 GMT

I use an i.MX 8 QuadMax Mek with 5.4.70-2.3.0

Edit: @jimmychan I guess you didn't get notified because I missed the proper reply button...

Re: LPDDR4 Temperature Sensor

philippe_schenk — Wed, 10 Feb 2021 09:13:53 GMT

Hi @jimmychan pinging you here again as I got a follow-up email from the community and I am not sure wether my edit before triggered a mail to you.

We're searching answers for i.MX 8QXP MEK, i.MX 8 QuadMax MEK, i.MX 8M EVK. We're currently developing on all three SoC variants and I guess the answer for all three is similar. But most important for now is the i.MX 8 QuadMax

Best Regards,
Philippe

Re: LPDDR4 Temperature Sensor

jimmychan — Wed, 10 Feb 2021 16:38:13 GMT

Hello,

Sorry to tell you that we don't have the example code for reading the MR4.

Basically, we have DDR test tool and the RPA (excel sheet) to configure/tuning the parameters.

For details, please read this link:

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/i-MX-8-8X-Family-DDR-Tools-Release/ta-p/1121519

Re: LPDDR4 Temperature Sensor

shusheer — Tue, 17 Jan 2023 22:36:52 GMT

Did you ever get code working to do this? I'm interested in reading LPDDR4 temperature sensor using i.MX8MPlus, which presumably is similar.

Re: LPDDR4 Temperature Sensor

philippe_schenk — Wed, 18 Jan 2023 08:16:00 GMT

Hi shusheer,

I'm sorry we never really went ahead with this idea.

But just a rough guess would be that this needs to be read out from the SCFW since also the RAM is being setup by the SC Firmware.

Best Regards,
Philippe

Re: LPDDR4 Temperature Sensor

shusheer — Mon, 12 Jun 2023 20:01:54 GMT

I have done some further digging on this, and am replying so others who find this info save some head-scratching.

It seems that the LPDDR4 temperature sensor is accessible through the MR4 mode register on the memory chip. However, MR4 does not provide raw temperature, it provides a set of bitfields that suggest the appropriate scaling of the memory refresh rate based on the raw temperature. There does not appear to (in general) be a way to get raw temperature measurements from the LPDDR4 module temperature sensor itself.

A representative datasheet describing the process is here:https://www.micron.com/-/media/client/global/documents/products/data-sheet/dram/mobile-dram/low-power-dram/lpddr4/z19m_embedded_lpddr4_lpddr4x.pdf see page 44 and page 190

So I assume it is usual for the operating system to regularly poll MR4, and then update the processor DDRC refresh registers. One could hook into this process to find out if the LPDDR4 is particularly high or low temperature.