On 09/18/14 15:46, Russell King - ARM Linux wrote: > On Thu, Sep 18, 2014 at 02:43:11PM -0700, Stephen Boyd wrote: >> diff --git a/arch/arm/include/asm/vfp.h b/arch/arm/include/asm/vfp.h >> index f4ab34fd4f72..76d3f6907cce 100644 >> --- a/arch/arm/include/asm/vfp.h >> +++ b/arch/arm/include/asm/vfp.h >> @@ -21,7 +21,7 @@ >> #define FPSID_FORMAT_MASK (0x3 << FPSID_FORMAT_BIT) >> #define FPSID_NODOUBLE (1<<20) >> #define FPSID_ARCH_BIT (16) >> -#define FPSID_ARCH_MASK (0xF << FPSID_ARCH_BIT) >> +#define FPSID_ARCH_MASK (0x7F << FPSID_ARCH_BIT) > This is incorrect. On VFPv2, the architecture field is four bits long. > As you can see from the above, bit 20 indicates that there are no > double operations provided, and the next two bits indicate the FSTMX/ > FLDMX format. > > I know that you're changing this to conform with the ARM ARM, but we > have to consider that before VFP was subsumed into the ARM ARM, this > register had the format described as per this file, and these other > bits may be set for an ARM part. Including these bits in the mask > means that we will mis-identify these older parts as VFPv3. > > Welcome to the lack of standardisation! >
Thank you for the warm welcome! I looked at the TRMs for ARM11 and ARM9. I can't find anywhere where VFPv2 is supported and these bits are set. Bits 22-16 of FPSID: ARM1136r1p5: 0x01 ARM1136r1p3: 0x01 ARM1176: 0x01 ARM11MPCorer2p0: 0x01 ARM11MPCorer1p0: 0x01 ARM1156: 0x01 ARM9: 0x01 Do you, or anyone else, know of other implementations? I *hope* that this same exercise was done by the VFP architects before they re-purposed bits but who knows. If nobody is actually setting these higher bits then is there any problem widening the mask (besides it being slightly confusing)? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
