From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Fri, 22 Feb 2013 15:46:18 -0800 Subject: [PATCH] ARM: vfp: fix fpsid register subarchitecture field mask width In-Reply-To: <20130222182705.GC19527@mudshark.cambridge.arm.com> References: <1361520485-30269-1-git-send-email-sboyd@codeaurora.org> <20130222182705.GC19527@mudshark.cambridge.arm.com> Message-ID: <5128034A.4000008@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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: >> From: Steve Muckle >> >> 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. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation