[Letux-kernel] 2GB vs. 4GB Pyra RAM tests

Dr. H. Nikolaus Schaller hns at goldelico.com
Mon Aug 14 11:02:53 CEST 2017


Hi, Great! Thanks!
We may have doubled the noise on ddr3  power with 4gb chips. New pcb layout may already be better.
Will try to test asap.

On the road.

> Am 14.08.2017 um 06:39 schrieb Tony Lindgren <tony at atomide.com>:
> 
> Hi,
> 
> * H. Nikolaus Schaller <hns at goldelico.com> [170811 13:25]:
>>> Am 11.08.2017 um 16:46 schrieb Tony Lindgren <tony at atomide.com>:
>>> and I noticed
>>> it would hang often while booting even with 2GB and no LPAE.
>>> I only saw any kind of oops once or twice, most of the time
>>> it just hung. Is this what you're seeing too?
>> 
>> Yes. 4GB CPU board randomly hangs - or succeeds to boot. 2GB boards
>> seem to boot fine every time.
> 
> So after tinkering with pyra-4g this weekend, here's what
> seems to work based on very light testing:
> 
> 1. Configure smps6 to 1.39V instead of 1.35V
> 
> So what does this mean? Not enough power from palmas or too
> low voltage for the 4GB DDR3 chip? Any ideas?
> 
> The 4GB DDR3 datasheet says "1.35V(1.28V~1.45V) & 1.5V(1.425V~1.575V)",
> so maybe we need to configure it to 1.35V separately somehow?
> 
> 2. Configure interleaving
> 
> Not sure if this is mandatory but needed for now it seems.
> 
> 3. Use igepv5 ddr3 timings instead of Matthij's timings
> 
> Have not checked what's different.. I'll post my WIP patches
> shortly and let's figure it out, maybe Matthijs can spot
> the differences :)
> 
>> That is the reason why we don't know for sure if it is a SW or HW effect.
>> It could also be HW induced because SW setup is not optimized.
> 
> Well the 1.39V need seems weird..
> 
>> AFAIK, there is a DRA7 tool to calculate some EMIF parameter block
>> which takes wire lengths from SoC to DDR3 into account. The EMIF
>> seems to be able to add some picoseconds here and there...
> 
> No idea about that, sounds like somebody who is more familiar
> with memory timings should try it out.
> 
>> We haven't done (and probably can't do) that for OMAP5 and Pyra.
>> And I don't exactly know where Mattijs got our EMIF setup from (maybe
>> IGEP5 wich different DDR3 PCB layout):
>> 
>> http://git.goldelico.com/?p=gta04-uboot.git;a=blobdiff;f=board/goldelico/letux-cortex15/lc15.c;h=280da2095da9a780475fe3d59e79d283b050f02d;hp=709865cbe0f10d389634924d3b57c5731c184429;hb=0c5e26e7886ea7d2d934f65e2e6cbf15a2b52bc8;hpb=be096ca0c2b204897b84c45e709511184b3a4059
> 
> Well something is still different with timings as the igepv5
> timings work now :p
> 
> $ cat /proc/cmdline
> console=ttyS2,115200 mem=2032M at 0x80000000 mem=2048M at 0x300000000 debug earlyprintk earlycon
> $ free
>             total       used       free     shared    buffers     cached
> Mem:       4115788     186528    3929260     149784          0     149784
> -/+ buffers/cache:      36744    4079044
> Swap:            0          0          0
> 
>> PS: if you can use a JTAG adapter, I could send you a SD-Card shaped
>> PCB with solder points for the OMAP5 JTAG signals. Here is a photo
>> (of the uncut PCB - I haven't access to a better photo this week):
> 
> I have not really needed JTAG for years, maybe a bit later thanks :)
> 
> Regards,
> 
> Tony


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