On 2/22/2013 10:27 AM, Will Deacon wrote:

Hi guys,

On Fri, Feb 22, 2013 at 08:08:05AM +0000, Stephen Boyd wrote:

quoted

From: Steve Muckle <redacted>

The subarchitecture field in the fpsid register is 7 bits wide.
The topmost bit is used to designate that the subarchitecture
designer is not ARM. We use this field to determine which VFP
version is supported by the CPU. Since the topmost bit is masked
off we detect non-ARM subarchitectures as supporting only
HWCAP_VFP and not HWCAP_VFPv3 as it should be for Qualcomm's
processors.

I'm struggling to see why this has anything to do with the hwcaps being set
incorrectly. What value do you have in fpsid? As far as I can tell, the
subarchitecture bits 6:0 should start at 0x40 for you, right?

Yes it does.

I can see cases for changing this code, I just don't see why it would go
wrong in the case you're describing.

VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;

causes VFP_arch to be equal to 0 because 0x40 & 0xf == 0.

and then a little bit later we have

               if (VFP_arch >= 2) {
                        elf_hwcap |= HWCAP_VFPv3;


The branch is not taken so we never set VFPv3.

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