Versatile Express randomly fails to boot - Versatile Express to be removed from nightly testing

[Russell King - ARM Linux]

On Tue, Mar 17, 2015 at 12:05:58PM +0000, Sudeep Holla wrote:
> As I had mentioned yesterday, I did compare the L2C settings between
> v3.18 and later kernel and found them to be *exactly same*.
> 
> Since you suspected issues around instruction fetching, I tried playing
> around the tag and data ram latencies. After some experiments, I found
> that changing just the tag ram read latency to 2 cycles, the issue we
> are seeing goes away at-least on my setup. It will be good to see the
> behaviour on your setup with the patch below.
> 
> The default value which bootmon is programming happens to be worst
> case scenario(8 cycles for all). Will recalls that it was changed to
> minimum value after graphics guys complained about performance.
> 
> We need to check with h/w guys to get the correct optimal values for
> these latencies.
> 
> Regards,
> Sudeep
> 
> --->8
> 
> diff --git a/arch/arm/boot/dts/vexpress-v2p-ca9.dts
> b/arch/arm/boot/dts/vexpress-v2p-ca9.dts
> index 23662b5a5e9d..030c90c1105d 100644
> --- a/arch/arm/boot/dts/vexpress-v2p-ca9.dts
> +++ b/arch/arm/boot/dts/vexpress-v2p-ca9.dts
> @@ -172,7 +172,7 @@
>                 interrupts = <0 43 4>;
>                 cache-level = <2>;
>                 arm,data-latency = <1 1 1>;
> -               arm,tag-latency = <1 1 1>;
> +               arm,tag-latency = <1 2 1>;

I've tried <1 2 1> and <1 8 1> here, I don't see any difference.  My test
build fails on the first boot attempt for each.

I notice you're only changing the write latency here.  Is that correct?
You mention read latency above.

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