[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[Vadim Bendebury]

This patch won't necessarily apply as it has not been verified on
a real hardware, so this is more of an RFC.

Vadim Bendebury (1):
  ARM: thumb: Fix thumb mode compilation problems.

 arch/arm/kernel/fiq.c         |   34 ++++++++++++++++++++++++++--------
 arch/arm/mach-tegra/headsmp.S |    3 ++-
 2 files changed, 28 insertions(+), 9 deletions(-)

-- 
1.7.3.1

[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[Dave Martin]

On Fri, May 13, 2011 at 12:58:45PM -0700, Vadim Bendebury wrote:
> 
> This patch won't necessarily apply as it has not been verified on
> a real hardware, so this is more of an RFC.
> 
> Vadim Bendebury (1):
>   ARM: thumb: Fix thumb mode compilation problems.
> 
>  arch/arm/kernel/fiq.c         |   34 ++++++++++++++++++++++++++--------
>  arch/arm/mach-tegra/headsmp.S |    3 ++-
>  2 files changed, 28 insertions(+), 9 deletions(-)
> 
> -- 
> 1.7.3.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

A different patch for this has already been discussed:

http://thread.gmane.org/gmane.linux.ports.arm.kernel/112864

It's a bit stalled on my side because I don't have a suitable platform
to test it on.  As some have suggested, in my case (imx51) the inclusion
of code was inherited from from an older subarch tree and is no longer
appropriate -- so my problem is actually solved just by not building
this code.

If the code is really used in your kernel (not just built) it would
be really useful if you could test this patch.

However you should definitely check whether the code is really used at
all on tegra.

There's a fair chance that it's not used: FIQ is not much used by linux
on armv7 and above: unless you make use of cache+TLB lockdown / SRAM etc.,
FIQ is unlikely to be significantly faster than IRQ on recent CPUs.  FIQ
may also get reserved for use by TrustZone on some platforms, complicating
the picture further. 

Cheers
---Dave

[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[Dave Martin]

On Fri, May 13, 2011 at 12:58:45PM -0700, Vadim Bendebury wrote:
> 
> This patch won't necessarily apply as it has not been verified on
> a real hardware, so this is more of an RFC.
> 
> Vadim Bendebury (1):
>   ARM: thumb: Fix thumb mode compilation problems.
> 
>  arch/arm/kernel/fiq.c         |   34 ++++++++++++++++++++++++++--------
>  arch/arm/mach-tegra/headsmp.S |    3 ++-
>  2 files changed, 28 insertions(+), 9 deletions(-)
> 

As a side note, I'm happy to be CC'd if you have Thumb-2 kernel problems
since I've been working on this recently, and would like to get it working
across the broadest range of platforms possible.

I'm definitely interested if you hit any non-platform-specific issues, since
I'm not too familiar with tegra.

So far, omap was the most "interesting" target: if you have problems, the
following commits for omap may contain examples of things you need to fix:

git log -i --grep=thumb -- arch/arm/mach-omap2 arch/arm/plat-omap

dd31394 ARM: omap3: Thumb-2 compatibility for sleep34xx.S
ef7a87d ARM: omap3: Thumb-2 compatibility for sram34xx.S
76d5001 ARM: omap3: Remove hand-encoded SMC instructions
f96bdfa ARM: omap4: Convert END() to ENDPROC() for correct linkage with CONFIG_THUMB2_KERNEL
85243a7 ARM: omap4: Provide do_wfi() for Thumb-2
b6338bd ARM: 6649/1: omap: use fncpy to copy the PM code functions to SRAM

[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[Colin Cross]

On Mon, May 16, 2011 at 3:38 AM, Dave Martin <dave.martin@linaro.org> wrote:
> On Fri, May 13, 2011 at 12:58:45PM -0700, Vadim Bendebury wrote:
>>
>> This patch won't necessarily apply as it has not been verified on
>> a real hardware, so this is more of an RFC.
>>
>> Vadim Bendebury (1):
>> ? ARM: thumb: Fix thumb mode compilation problems.
>>
>> ?arch/arm/kernel/fiq.c ? ? ? ? | ? 34 ++++++++++++++++++++++++++--------
>> ?arch/arm/mach-tegra/headsmp.S | ? ?3 ++-
>> ?2 files changed, 28 insertions(+), 9 deletions(-)
>>
>> --
>> 1.7.3.1
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> A different patch for this has already been discussed:
>
> http://thread.gmane.org/gmane.linux.ports.arm.kernel/112864
>
> It's a bit stalled on my side because I don't have a suitable platform
> to test it on. ?As some have suggested, in my case (imx51) the inclusion
> of code was inherited from from an older subarch tree and is no longer
> appropriate -- so my problem is actually solved just by not building
> this code.
>
> If the code is really used in your kernel (not just built) it would
> be really useful if you could test this patch.
>
> However you should definitely check whether the code is really used at
> all on tegra.
>
> There's a fair chance that it's not used: FIQ is not much used by linux
> on armv7 and above: unless you make use of cache+TLB lockdown / SRAM etc.,
> FIQ is unlikely to be significantly faster than IRQ on recent CPUs. ?FIQ
> may also get reserved for use by TrustZone on some platforms, complicating
> the picture further.

Most Android kernels, including on Tegra, use the FIQ handler for a
simple debugger on the serial console.   Sending a break will enter
debugger mode, which can dump backtraces from FIQ context, even if the
CPU is stuck in an IRQ, or with IRQs off.

We've never used a Thumb2 kernel though.

[PATCH 0/1] ARM: thumb: Fix thumb mode compilation problems.

[Dave Martin]

On Mon, May 16, 2011 at 09:06:26AM -0700, Colin Cross wrote:
> On Mon, May 16, 2011 at 3:38 AM, Dave Martin <dave.martin@linaro.org> wrote:
> > On Fri, May 13, 2011 at 12:58:45PM -0700, Vadim Bendebury wrote:
> >>
> >> This patch won't necessarily apply as it has not been verified on
> >> a real hardware, so this is more of an RFC.
> >>
> >> Vadim Bendebury (1):
> >> ? ARM: thumb: Fix thumb mode compilation problems.
> >>
> >> ?arch/arm/kernel/fiq.c ? ? ? ? | ? 34 ++++++++++++++++++++++++++--------
> >> ?arch/arm/mach-tegra/headsmp.S | ? ?3 ++-
> >> ?2 files changed, 28 insertions(+), 9 deletions(-)
> >>
> >> --
> >> 1.7.3.1
> >>
> >>
> >> _______________________________________________
> >> linux-arm-kernel mailing list
> >> linux-arm-kernel at lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >
> > A different patch for this has already been discussed:
> >
> > http://thread.gmane.org/gmane.linux.ports.arm.kernel/112864
> >
> > It's a bit stalled on my side because I don't have a suitable platform
> > to test it on. ?As some have suggested, in my case (imx51) the inclusion
> > of code was inherited from from an older subarch tree and is no longer
> > appropriate -- so my problem is actually solved just by not building
> > this code.
> >
> > If the code is really used in your kernel (not just built) it would
> > be really useful if you could test this patch.
> >
> > However you should definitely check whether the code is really used at
> > all on tegra.
> >
> > There's a fair chance that it's not used: FIQ is not much used by linux
> > on armv7 and above: unless you make use of cache+TLB lockdown / SRAM etc.,
> > FIQ is unlikely to be significantly faster than IRQ on recent CPUs. ?FIQ
> > may also get reserved for use by TrustZone on some platforms, complicating
> > the picture further.
> 
> Most Android kernels, including on Tegra, use the FIQ handler for a
> simple debugger on the serial console.   Sending a break will enter
> debugger mode, which can dump backtraces from FIQ context, even if the
> CPU is stuck in an IRQ, or with IRQs off.
> 
> We've never used a Thumb2 kernel though.

Fair enough -- in that case I guess it may be needed.

Sounds like entering the debugger will help in testing this; I don't have
the board myself though.

---Dave