AM62P: Ability to support 12GB RAM?

Hi David,

From what I saw in the datasheet the MT53E384M32D2DS-053 AAT:E is a 12Gbit part (not 12GByte) and hence 12/8 = 1.5GB. Will let James comment on the rest but can you please confirm how much of this DDR are they able to use?

Regards

Karan

Hi Karan,

Yes it's a 12Gbit part, 2 channels of 6Gb (not 2 ranks) and there's no way to configure that in the SysConfig tool. The customer patched in u-boot enabling some register that allowed non power of 2sizes.

But as I recall, only 1/2 of the memory was accessible from early u-boot, then 1/4 of it for later u-boot. 

Sincerely,

David

Hi David,

James is out of office this week. Please expect delay response from him.

Hi David,

we only have support for power-of-2 densities of memory.  So they should be able to configure for 16Gb in the SysConfig tool and be able to access 8Gb of the memory.

Do they want to be able to access all 12Gb?  If so, I would have to investigate if that is possible.  There may be some tweaks to the address configuration registers we can do, but i can't guarantee anything at the moment. 

Regards,

James  

Hi James,

The customer said the following: 

"Not sure how you can get 8Gb to work when it's two channels of 6Gb? That smells fishy.

We picked that size of memory because it was the lower end of what we considered we would need.  And because 16Gb was more than we needed and much more expensive. Could we live with 8Gb, maybe..."

Is there any explanation I can provide to the customer in regards to enabling 2x channels of 6Gb?

I am also working with the customer to confirm the amount of RAM that is needed to get this to work. 

Sincerely,
David

David,

Do they have a board with 12Gb on it?  Or are they just investigating what they will need?

I suggested configuring 8Gb just to see if it would work.  I think it would enable 4Gb on each channel.  Or they could try the 16Gb configuration.  If they already have a board, these attempts would take just a few minutes each.  I'm just trying to get to a quick solution. 

Again, i emphasize that the DDR config tool is only designed for power-of-2 memories, so i'm just trying to work with what we have today.

If they absolutely need to get all 12Gb to function, this will take some new investigation and changes to the DDR config tool on my side (ie, i have to plan it around everything else i'm working on), so it will take some time.  And i don't readily have any hardware to test it (again, will take time to procure this)

Regards,

James

Hi JJD,

The customer shared the following:

Our board is populated with 12Gb yes and we also have a board with 8Gb, I can't recall what I tried.  I don't think the 8Gb config worked on the 12Gb without enabling the odd size in some register.  But the 12Gb config worked on the 8Gb ram even with the odd size enabled.  I know that sounds weird, but that's what I remember. If you want to build a uboot binary to run 8Gb on the 12Gb, I'm happy to try it. 

We bought a few thousand pieces of the 12Gb before the prices went insane because 12Gb is enough for our applications.  If we had our pick of memory we'd probably be using 16Gb not 8Gb. We can't build this product if we can't use the memory.  Could we make8Gb work, perhaps.  I don't know what features we may lose.  We don't have hardware to give the software team yet...

Sincerely,
David

Hi David, i looked into this a bit. 

Have them generate a 16Gb, 1 rank configuration using the DDR register configuration tool, then make the following manual change in the config file:

### 16Gb Configuration (1 rank, 2GB):
DENALI_CTL_327 = 0x007FF00   // CS_MAP_NON_POW2=0 (power-of-2 mode)

### 12Gb Configuration (1 rank, 1.5GB):
DENALI_CTL_327 = 0x037FF00   // CS_MAP_NON_POW2=3 (non-pow2 enabled)

I don't have hardware to check this out, but would like to see if they can try this on their boards.

Regards,

James

Hi James,

Just posting a response to keep the thread from locking.

Sincerely,
David

Hi James,

I heard back from Algo on this while I was out. They used the sysconfig tool from the browswer and regenerated for 16Gb 1 rank, per your instructions.  It gave me the attached payload. 

The file k3-am62Px-ddr-config.dtsi was copied into u-boot as: arch/arm/dts/k3-am62p-ddr-lp4-50-1600.dtsi 
Then they looked for DENALI_CTL_327 and it's not in that file. It's also not in the zip file they got from the sysconfig tool, and when they search u-boot for the string: grep -Irn "DENALI_CTL_327 = 0x007FF00" 
And got no hits. 

The following zip file was also shared: 5148.all.zip

If there is any additional info you need, please let me know.

Sincerely,
David

line 327 of k3-am62Px-ddr-config.dtsi 

#define DENALI_CTL_327  0x0037FF00

Regards,
James

Hi James,

Just for some additional clarity, Stef shared the following:

I've already copied from sysconfig to k3-am62p-ddr-lp4-50-1600.dtsi (I'm using the 8Gb file) and as I mentioned,  there's no DENALI_CTL_327 in: ti-u-boot-2025.01+git/arch/arm/dts/k3-am62p-ddr-lp4-50-1600.dtsi that was already copied from sysconfig. By extension, I'll say there's no DENALI_CTL_327 in the file I used from sysconfig. See the attached sysconfig screens.  And I attached the output(all.zip), and it's not in that file.

All_2.zip

Was there something I might've missed sending over to the customer?

Sincerely,
David

Sorry, I had the wrong prefix.  DENALI_CTL_xxx = DDRSS_CTL_xxx

They need to try with the following change:

-#define DDRSS_CTL_327_DATA 0x00FFFF00

+#define DDRSS_CTL_327_DATA 0x03FFFF00

Regards,
James