linux-kernel - Re: [PATCH] arm64: cpufeature: Enable Qualcomm Falkor errata 1009 for Kryo

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Message-ID: <20191029172431.GY571@minitux>
Date:   Tue, 29 Oct 2019 10:24:31 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Will Deacon <will@...nel.org>
Cc:     Jeffrey Hugo <jhugo@...eaurora.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] arm64: cpufeature: Enable Qualcomm Falkor errata 1009
 for Kryo

On Tue 29 Oct 10:11 PDT 2019, Will Deacon wrote:

> On Tue, Oct 29, 2019 at 09:07:53AM -0600, Jeffrey Hugo wrote:
> > On 10/29/2019 7:44 AM, Jeffrey Hugo wrote:
> > > On 10/29/2019 4:50 AM, Will Deacon wrote:
> > > > On Mon, Oct 28, 2019 at 11:06:04PM -0700, Bjorn Andersson wrote:
> > > > > The Kryo cores share errata 1009 with Falkor, so add their model
> > > > > definitions and enable it for them as well.
> > > > > 
> > > > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > > > ---
> > > > >   arch/arm64/include/asm/cputype.h | 4 ++++
> > > > >   arch/arm64/kernel/cpu_errata.c   | 2 ++
> > > > >   2 files changed, 6 insertions(+)
> > > > > 
> > > > > diff --git a/arch/arm64/include/asm/cputype.h
> > > > > b/arch/arm64/include/asm/cputype.h
> > > > > index b1454d117cd2..8067476ea2e4 100644
> > > > > --- a/arch/arm64/include/asm/cputype.h
> > > > > +++ b/arch/arm64/include/asm/cputype.h
> > > > > @@ -84,6 +84,8 @@
> > > > >   #define QCOM_CPU_PART_FALKOR_V1        0x800
> > > > >   #define QCOM_CPU_PART_FALKOR        0xC00
> > > > >   #define QCOM_CPU_PART_KRYO        0x200
> > > > > +#define QCOM_CPU_PART_KRYO_GOLD        0x211
> > > > > +#define QCOM_CPU_PART_KRYO_SILVER    0x205
> > > 
> > > These are not Kryo part numbers (8998+).  They are Hydra ones.
> > > 
> > > > 
> > > > Can you double-check this, please? My Pixel-1 phone claims something with
> > > > 0x201, but I don't know if that's what you were aiming for. It would be
> > > > great if Qualcomm could document these register fields somewhere,
> > > > especially
> > > > since we're trying to work around their hardware errata for them.
> > > 
> > > I wish I could point you to public documentation.  I don't happen to
> > > know where it is.  As far as 8996 goes, there are quite a few part
> > > numbers.  The ones I could find are:
> > > 201
> > > 205
> > > 211
> > > 241
> > > 251
> > > 
> > > 281 happens to be QDF2432
> > 
> > From asking around, I found someone in the know.  We don't have public
> > documentation, but I can follow up to try to create something - its likely
> > going to take a bit.  I was given the following information to share.  This
> > is specific to Hydra only-
> > 
> > MIDR[15:12] = PART[11:8]
> > Hydra and technology node differentiator (0x1 = Hydra 16nm; 0x2 = Hydra
> > 14nm; 0x3 = Hydra 10nm)
> > 
> > MIDR[11:10] = PART[7:6]
> > This corresponds to the cluster revision number
> > 
> > MIDR[9:8] = PART[5:4]
> > Technology variant within the node
> > 
> > MIDR[7:6] = PART[3:2]
> > 0b00 = 512KB L2
> > 0b01 = 1MB L2
> > 0b10 = 2MB L2
> > 0b11 = 4MB L2
> > 
> > MIDR[5:4] = PART[1:0]
> > 0b00 = uni-core
> > 0b01 = dual-core cluster
> > 0b10 = tri-core cluster
> > 0b11 = quad-core cluster
> 
> Thanks for digging up the details, Jeffrey. As far as I can tell, our
> 'is_kryo_midr()' function will return 'true' for all of these, so I think
> that's what we should be using for this erratum workaround. Would that work
> for you?
> 

Yes, I agree. There's a fair amount of variants involved, so let's go
for is_kryo_midr() (which should be is_hydra_midr()).

Regards,
Bjorn