* Sekhar Nori <nsekhar@xxxxxx> [140709 05:28]:
> On Wednesday 09 July 2014 02:55 PM, Tony Lindgren wrote:
> > * Tony Lindgren <tony@xxxxxxxxxxx> [140708 01:32]:
> >> * Sekhar Nori <nsekhar@xxxxxx> [140707 21:56]:
> >>> On Monday 07 July 2014 08:40 PM, Felipe Balbi wrote:
> >>>> On Mon, Jul 07, 2014 at 02:40:08PM +0100, Russell King - ARM Linux wrote:
> >>>>> --- a/arch/arm/mm/cache-l2x0.c
> >>>>> +++ b/arch/arm/mm/cache-l2x0.c
> >>>>> @@ -732,7 +732,7 @@ static int l2c310_cpu_enable_flz(struct notifier_block *nb, unsigned long act, v
> >>>>>
> >>>>> static void __init l2c310_enable(void __iomem *base, u32 aux, unsigned num_lock)
> >>>>> {
> >>>>> - unsigned rev = readl_relaxed(base + L2X0_CACHE_ID) & L2X0_CACHE_ID_PART_MASK;
> >>>>> + unsigned rev = readl_relaxed(base + L2X0_CACHE_ID) & L2X0_CACHE_ID_RTL_MASK;
> >>>>> bool cortex_a9 = read_cpuid_part() == ARM_CPU_PART_CORTEX_A9;
> >>>>
> >>>> even with this change, l2c still tries to write to power control
> >>>> register, at least on AM437x. Looking a little deeper here, AM437x
> >>>> identifies itself as l2c PL310 r3p3, which should have power control
> >>>> register, but aparentely there's no way to write that register. I'll
> >>>> file a bug to our ROM team, but we will certainly need a way to
> >>>> workaround this inside omap4-common.c
> >>>
> >>> Looks like we need both my patch as well as Russell's patch. I can
> >>> respin my patch with the pr_info_once() dropped if it helps further
> >>> reduce boot noise.
> >>
> >> In that case I'm fine with the original patch in this series. Russell,
> >> got any better ideas?
> >
> > I guess no more comments. Took a look at the patch again, Sekhar, can
> > you please update the description with what has been discovered in this
> > thread and repost?
>
> How does the following sound:
>
> ---
> AM437x has L2C-310 version r3p2 and ROM code on that device does not
> support writing to L2C-310 power control register. The L2C driver,
> however, tries writing to this register for all revisions >= r3p0.
>
> This leads to a warning dump on boot which leads most users to believe
> that L2 cache is non-functional.
>
> Since the problem is understood, and cannot be addressed through
> software, replace the warning with a pr_info() while maintaining the
> WARN_ON() for other truly unexpected scenarios.
>
> From the public TRM available for OMAP4470, even on that device, ROM
> does not support writing to this register even though it uses a version
> of L2C-310 which has the register implemented. So this patch should take
> care of all variants of existing OMAPs.
> ---
>
> Two things that I have added are the version of L2C on AM437x and the
> fact that OMAP4470 also has the same issue (at least from the public
> TRM). Let me know if you would like to see anything else mentioned.
Looks good to me thanks.
Tony
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