[PATCH v2] ARM: Do not run dummy_flush_tlb_a15_erratum() on non-Cortex-A15
Russell King - ARM Linux
linux at arm.linux.org.uk
Thu Aug 1 16:15:15 EDT 2013
On Thu, Aug 01, 2013 at 03:09:51PM -0500, Rob Herring wrote:
> On Thu, Aug 1, 2013 at 5:58 AM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
> > On Wed, Jul 31, 2013 at 11:03:46PM -0500, Rob Herring wrote:
> >> I just submitted my patch for 798181 ECO fix handling to the patch
> >> system today. Then I noticed this patch in your fixes branch. This is
> >> going to cause some churn as my patch needs to move the core version
> >> check back to a .c file.
> >> I don't know if you are okay with rebasing your fixes branch or not.
> >> If my patch is applied first, then this issue can be handled by just
> >> replacing dummy_flush_tlb_a15_erratum call in context.c a call to
> >> erratum_a15_798181.
> > Well, firstly, are you sure your patch is correct?
> > You're removing the call to dummy_flush_tlb_a15_erratum() before the
> > smp_call_function() - smp_call_function() does _not_ call the function
> > for the local CPU. So, what this means is we don't end up doing any
> > of the workaround for the local CPU.
> No, dummy_flush_tlb_a15_erratum() is now called from within
> erratum_a15_798181 if errata_fix_needed is non-zero. The return value
> only means do the IPI or not.
> > Secondly, doesn't the check in your case reduce down to:
> > unsigned int midr = read_cpuid_id();
> > /* Cortex-A15 r0p0..r3p2 affected */
> > if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2 ||
> > /* ECO not fully fixed */
> > !(read_cpuid(CPUID_REVIDR) & 0x010))
> > return 0;
> > return 1;
> > because, assuming midr is not satisfied:
> > revidr errata_fix_needed function return
> > 000 2 1
> > 010 1 0
> > 200 2 1
> > 210 0 0
> > I think that the above version is still cheap enough to be inline.
> Only because it is incomplete. :)
Your timing is very bad. I just sent the entire fixes branch (and some
other stuff - which was scheduled for a long time to be sent tonight)
off to Linus having waited all day. It was either that or sit on the
fixes branch even longer.
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