ARM: thumb: Fix thumb mode compilation problems.

Quoted 34 lines · Dave Martin

Quoted 11 lines · 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(-)

Quoted 8 lines

--
1.7.3.1

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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.

Quoted 8 lines

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.