Re: [RESEND][PATCH] ARM errata, 430973: update the affected revisions

Re: [RESEND][PATCH] ARM errata, 430973: update the affected revisions

[Tony Lindgren]

* Tony Lindgren <tony@atomide.com> [150413 07:46]:
> * Jeroen Hofstee <linux-arm@myspectrum.nl> [150411 02:26]:
> > Hello Russell, +Tony,
> > 
> > Thanks for taking the time to respond,
> > 
> > On 11-04-15 09:52, Russell King - ARM Linux wrote:
> > >On Fri, Apr 10, 2015 at 11:29:13PM +0200, Jeroen Hofstee wrote:
> > >>On 25-02-15 20:36, Jeroen Hofstee wrote:
> > >>>On 09-12-14 14:30, Jeroen Hofstee wrote:
> > >>>>From: Jeroen Hofstee <linux-arm@myspectrum.nl>
> > >>>>
> > >>>>Update the list of revisions subject to this errata.
> > >>>>
> > >>>>Cc: Catalin Marinas <catalin.marinas@arm.com>
> > >>>>Cc: Russell King <rmk+kernel@arm.linux.org.uk>
> > >>>>Cc: Andreas Bießmann <andreas.devel@googlemail.com>
> > >>>>Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
> > >>>>---
> > >>>>I don't have access to the AT400/AT401/AT490 document, but
> > >>>>Andreas was kind enough to provide this information, see
> > >>>>https://www.mail-archive.com/u-boot@lists.denx.de/msg156620.html
> > >>>>
> > >>>>Resending from an address which is subscribed to the ML...
> > >>>>---
> > >>>>  arch/arm/Kconfig | 2 +-
> > >>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> > >>>>
> > >>>>diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > >>>>index 89c4b5c..a2202fa 100644
> > >>>>--- a/arch/arm/Kconfig
> > >>>>+++ b/arch/arm/Kconfig
> > >>>>@@ -1063,7 +1063,7 @@ config ARM_ERRATA_430973
> > >>>>      depends on CPU_V7
> > >>>>      help
> > >>>>        This option enables the workaround for the 430973 Cortex-A8
> > >>>>-      (r1p0..r1p2) erratum. If a code sequence containing an ARM/Thumb
> > >>>>+      (r1p0..r1p3, r1p7) erratum. If a code sequence containing an
> > >>>>ARM/Thumb
> > >>>>        interworking branch is replaced with another code sequence at
> > >>>>the
> > >>>>        same virtual address, whether due to self-modifying code or
> > >>>>virtual
> > >>>>        to physical address re-mapping, Cortex-A8 does not recover from
> > >>>>the
> > >>>
> > >No.  If you read the discussion that the OMAP people are having, it is
> > >unclear whether r3p2 is actually affected by this errata or not.
> > I scanned through it, but that is a different issue it seems. This patch
> > only adds r1p3 and r1p7 to the documentation, since according to ARM
> > they are affected by this errata. Newer revision should not be affected
> > by this errata (or ARM reintroduced it).
> > 
> > The patch is _not_ adding r3p2 as an affected version. And is also not
> > about how to deal with cores no longer needing this workaround.
> 
> Right.. But it seems that having the aux ctrl register bit enabled
> without doing the flush btac part leads into a different set of
> issues.
>  
> > >In the discussion with OMAP people, we've come up with a potentially
> > >better solution to this, which is to rearrange the code so that only
> > >Cortex-A8 executes this workaround, and the BTB flush is always
> > >present (which Tony says fixes the problem.)
> > 
> > The am3517 / r1p7 is a Cortex-a8 and is affected by this errata. I fail to
> > see why making this cortex-a8 specific will help anything about the revision
> > not being mentioned in the help text. (unless the CONFIG option gets
> > completely
> > removed).
> > >Meanwhile, OMAP people are seeing about updating uboot to set/clear
> > >the auxiliary control register bit appropriately for the revision of
> > >the core.
> > Well almost appropriately. [1] suggest "the bootloaders can be fixed
> > Cortex-A8
> > revisions later than r1p2 to not set the IBE bit.". That should have been
> > r1p7 as
> > well.
> > 
> > >In any case, adding the patch and suggesting people enable this for
> > >more Cortex-A8's (eg, non-OMAP) won't actually do anything in a
> > >multiplatform kernel.
> > >
> > Can you give an example of a r1p7 not needing the workaround?
> 
> Do you have some pointer for the documentation mentioning r1p7 is
> affected? It is possible that the revision range is wrong.. But I'm
> more likely to believe it is correct and we're hitting a different
> problem.
> 
> I'm hoping that with Russell's patch and my patch in the thread
> below, you don't necessarily need to enable 430973. That's these
> two patches:
> 
> http://www.spinics.net/lists/arm-kernel/msg411433.html
> http://www.spinics.net/lists/arm-kernel/msg411038.html
> 
> If what Russell and I are saying is correct, with the above two
> patches your system should behave properly with 430973 even if
> bit 6 in the aux ctrl register is set (or unset) by the bootloader.
> 
> If r1p7 is behaves with bit 6 cleared and errata 430973 set, then
> we know r1p7 is unaffected by 430973.

Sorry let's take this part again:

If r1p7 is behaves with bit 6 cleared and errata 430973 _unset_,
then we know r1p7 is unaffected by 430973.

Regards,

Tony
  
> > http://www.spinics.net/lists/arm-kernel/msg411297.html
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [RESEND][PATCH] ARM errata, 430973: update the affected revisions

[Russell King - ARM Linux]

On Mon, Apr 13, 2015 at 09:28:09AM -0700, Tony Lindgren wrote:
> * Tony Lindgren <tony@atomide.com> [150413 07:46]:
> > If what Russell and I are saying is correct, with the above two
> > patches your system should behave properly with 430973 even if
> > bit 6 in the aux ctrl register is set (or unset) by the bootloader.
> > 
> > If r1p7 is behaves with bit 6 cleared and errata 430973 set, then
> > we know r1p7 is unaffected by 430973.
> 
> Sorry let's take this part again:
> 
> If r1p7 is behaves with bit 6 cleared and errata 430973 _unset_,
> then we know r1p7 is unaffected by 430973.

I've asked.  The errata applies to _all_ Cortex A8 r1pX versions.
This is actually what the code in the kernel does today, but the
documentation does not reflect it.  So, I've updated the
documentation to reflect (a) the code and (b) the info I received:

http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?id=59552cc87cb6

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

Re: [RESEND][PATCH] ARM errata, 430973: update the affected revisions

[Tony Lindgren]

* Russell King - ARM Linux <linux@arm.linux.org.uk> [150413 14:37]:
> On Mon, Apr 13, 2015 at 09:28:09AM -0700, Tony Lindgren wrote:
> > * Tony Lindgren <tony@atomide.com> [150413 07:46]:
> > > If what Russell and I are saying is correct, with the above two
> > > patches your system should behave properly with 430973 even if
> > > bit 6 in the aux ctrl register is set (or unset) by the bootloader.
> > > 
> > > If r1p7 is behaves with bit 6 cleared and errata 430973 set, then
> > > we know r1p7 is unaffected by 430973.
> > 
> > Sorry let's take this part again:
> > 
> > If r1p7 is behaves with bit 6 cleared and errata 430973 _unset_,
> > then we know r1p7 is unaffected by 430973.
> 
> I've asked.  The errata applies to _all_ Cortex A8 r1pX versions.
> This is actually what the code in the kernel does today, but the
> documentation does not reflect it.  So, I've updated the
> documentation to reflect (a) the code and (b) the info I received:
> 
> http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?id=59552cc87cb6

OK thanks for checking it, that should clear quite a bit of confusion.

Regards,

Tony

Re: [RESEND][PATCH] ARM errata, 430973: update the affected revisions

[Jeroen Hofstee]

Hello Russell,

On 13-04-15 23:35, Russell King - ARM Linux wrote:
> On Mon, Apr 13, 2015 at 09:28:09AM -0700, Tony Lindgren wrote:
>> * Tony Lindgren <tony@atomide.com> [150413 07:46]:
>>> If what Russell and I are saying is correct, with the above two
>>> patches your system should behave properly with 430973 even if
>>> bit 6 in the aux ctrl register is set (or unset) by the bootloader.
>>>
>>> If r1p7 is behaves with bit 6 cleared and errata 430973 set, then
>>> we know r1p7 is unaffected by 430973.
>> Sorry let's take this part again:
>>
>> If r1p7 is behaves with bit 6 cleared and errata 430973 _unset_,
>> then we know r1p7 is unaffected by 430973.
> I've asked.  The errata applies to _all_ Cortex A8 r1pX versions.
> This is actually what the code in the kernel does today, but the
> documentation does not reflect it.  So, I've updated the
> documentation to reflect (a) the code and (b) the info I received:
>
> http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?id=59552cc87cb6
>

Good, that also matches with the patch I posted, [r1p4 .. r1p6]
are not necessarily not affected, they simply are not mentioned in the
errata. r1p7 is the last from the r1pX range. From r2p1 on things should
no longer need to workaround.

Regards,
Jeroen