On 7 September 2017 at 07:05, Tony Lindgren tony@atomide.com wrote:
I was wondering about the weird non-sensical 0xffff ref_ctrl and was thinking maybe we have multiple clocks going? And by setting ref_ctrl to 0xffff we stop their interaction for most part and this allowed me to boot kernel and run memtester..
Sorry, this doesn't make any sense to me.
If I'd have to speculate why severely reducing the refresh rate helps for you I'd lean towards its impact on power consumption pattern and resulting noise on vdd_ddr.
Regardless, it's a doomed solution since inadequate refreshing means that infrequently accessed memory locations will be prone to eventual corruption. (This is something that memtester presumably won't catch?)
Anyways, setting bit 20 to disable DDR3 internal DLL
I already mentioned this on irc, but I'll say it here too: disabling the ram DLL is a really strange thing to do, and I'm quite surprised that the ram continues to operate at all with DLL disabled at 532 MHz. DLL-disabled mode is intended only to allow ddr3 memory to be usable at very low frequencies (below 300 MHz) where the DLL may fail to lock, and the timings in this mode are very poorly specified.
Matthijs