[U-Boot] [PATCH] configs: Lower Lamobo R1 DRAM clock rate to 384 MHz

[Paul Kocialkowski]

Hi,

On Mon, 2018-06-18 at 09:59 +0200, Maxime Ripard wrote:
> On Fri, Jun 15, 2018 at 10:52:39PM +0200, Paul Kocialkowski wrote:
> > When running at 432 MHz, the Lamobo R1 DRAM tends to get corrupted under
> > stressing workloads. Reducing the clock rate to 384 MHz results in
> > significantly-improved stability.
> > 
> > One reliable way to trigger a corruption at 432 MHz is to run
> > I/O-intensive operations on an attached SATA disk. The same operations
> > when operating the DRAM at 384 MHz typically go fine.
> > 
> > For some unexplained reason, running at 408 MHz worsens the situation.
> > 
> > Signed-off-by: Paul Kocialkowski <contact at paulk.fr>
> 
> What RAM settings are used by the Allwinner BSP, and can you reproduce
> the issue there if they are the same?

I forgot to mention it, but the fex uses 432 MHz (just like the u-boot
defconfig we have currently). I doubt that building the Allwinner boot
software (boot0 and so on) for comparison is really an option at this
point, due to the trainwreck of build issues that may occur.

Would the linux-sunxi downstream u-boot be sufficient for this?

For the sake of completeness, I also looked whether enabling ODT for 432
MHz could be a solution, but since the fex does not make use of it (and
has the default Zq value of 0x7f), this is not an option.

Cheers,

Paul

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