From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Martin Subject: Re: [PATCH v3 6/7] arm64: Advertise ARM64_HAS_DCPODP cpu feature Date: Tue, 2 Apr 2019 15:59:58 +0100 Message-ID: <20190402145958.GJ3567@e103592.cambridge.arm.com> References: <20190401104515.39775-1-andrew.murray@arm.com> <20190401104515.39775-7-andrew.murray@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190401104515.39775-7-andrew.murray@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Andrew Murray Cc: Mark Rutland , libc-alpha@sourceware.org, Szabolcs Nagy , Catalin Marinas , Will Deacon , Phil Blundell , linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-api@vger.kernel.org On Mon, Apr 01, 2019 at 11:45:14AM +0100, Andrew Murray wrote: > Advertise ARM64_HAS_DCPOP when both DC CVAP and DC CVADP are supported. Do you mean ARM64_HAS_DCPODP? And do we need this? This capability flag doesn't currently appear to be used for anything (which makes me wonder whether it _should_ be wired up to something in the kernel). Do we expect the kernel to do something special with this in the future? OTOH, we get a nice printk when the feature is detected, and the code size cost is insignificant. So, if there's a reasonable expectation that we will use it someday, I don't see a big problem with having it. Cheers ---Dave > > Signed-off-by: Andrew Murray > --- > arch/arm64/include/asm/cpucaps.h | 3 ++- > arch/arm64/kernel/cpufeature.c | 9 +++++++++ > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h > index f6a76e43f39e..defdc67d9ab4 100644 > --- a/arch/arm64/include/asm/cpucaps.h > +++ b/arch/arm64/include/asm/cpucaps.h > @@ -61,7 +61,8 @@ > #define ARM64_HAS_GENERIC_AUTH_ARCH 40 > #define ARM64_HAS_GENERIC_AUTH_IMP_DEF 41 > #define ARM64_HAS_IRQ_PRIO_MASKING 42 > +#define ARM64_HAS_DCPODP 43 > > -#define ARM64_NCAPS 43 > +#define ARM64_NCAPS 44 > > #endif /* __ASM_CPUCAPS_H */ > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 5e27d2dbe45e..c74b25895c43 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1339,6 +1339,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = { > .field_pos = ID_AA64ISAR1_DPB_SHIFT, > .min_field_value = 1, > }, > + { > + .desc = "Data cache clean to Point of Deep Persistence", > + .capability = ARM64_HAS_DCPODP, > + .type = ARM64_CPUCAP_SYSTEM_FEATURE, > + .matches = has_cpuid_feature, > + .sys_reg = SYS_ID_AA64ISAR1_EL1, > + .field_pos = ID_AA64ISAR1_DPB_SHIFT, > + .min_field_value = 2, > + }, > #endif > #ifdef CONFIG_ARM64_SVE > { > -- > 2.21.0 >