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

Tony Lindgren tony at atomide.com
Mon Aug 14 16:13:33 CEST 2017


* Matthijs van Duin <matthijsvanduin at gmail.com> [170814 02:31]:
> On 14 August 2017 at 06:39, Tony Lindgren <tony at atomide.com> wrote:
> > 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?
> 
> One thought that crossed my mind is that the 60Ω termination value
> configured in the ram might be inappropriate with two ranks. This
> value is configured in bits 24-26 of sdram_config:
> 0 = no termination
> 2 = 120Ω
> 1 = 60Ω
> 
> I think it would be worth testing 120Ω termination or even no
> termination at all (this should work if the drive strength on the omap
> side matches the traces to ram, and would reduce power consumption).

OK will give it a try hopefully at some point later on tonight.

> > 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?
> 
> No

OK

> > 2. Configure interleaving
> >
> > Not sure if this is mandatory but needed for now it seems.
> 
> It is desirable for performance.

But also seemed necessary to have somehow based on brief my
testing last night :)

Regards,

Tony


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