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Message-ID: <8751bc38-9020-ba5f-d2d6-dd7486e1709a@arm.com>
Date: Fri, 30 Sep 2022 09:37:04 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Mark Brown <broonie@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, peterz@...radead.org,
acme@...nel.org, mark.rutland@....com, will@...nel.org,
catalin.marinas@....com, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH V3 1/7] arm64/perf: Add BRBE registers and fields
On 9/29/22 16:59, Mark Brown wrote:
> On Thu, Sep 29, 2022 at 01:28:51PM +0530, Anshuman Khandual wrote:
>
> Thanks for doing this work - I did spot a few small issues though.
>
>> /* id_aa64dfr0 */
>> +#define ID_AA64DFR0_BRBE_SHIFT 52
>> #define ID_AA64DFR0_MTPMU_SHIFT 48
>> #define ID_AA64DFR0_TRBE_SHIFT 44
>> #define ID_AA64DFR0_TRACE_FILT_SHIFT 40
>> @@ -848,6 +952,9 @@
>> #define ID_AA64DFR0_PMSVER_8_2 0x1
>> #define ID_AA64DFR0_PMSVER_8_3 0x2
>>
>> +#define ID_AA64DFR0_BRBE 0x1
>> +#define ID_AA64DFR0_BRBE_V1P1 0x2
>> +
>> #define ID_DFR0_PERFMON_SHIFT 24
>>
>> #define ID_DFR0_PERFMON_8_0 0x3
>
> This is already done in -next as a result of ID_AA64DFR0_EL1 being
> converted, the enumberation define comes out as
> ID_AA64DFR0_EL1_BRBE_BRBE_V1P1.
Right. I will rebase the series on upcoming 6.1-rc1 which should have all the
current -next patches including ID_AA64DFR0_EL1 migration into tools/sysreg.
This should just fall in place.
>
>> +# This is just a dummy register declaration to get all common field masks and
>> +# shifts for accessing given BRBINF contents.
>> +Sysreg BRBINF_EL1 2 1 8 0 0
>> +Res0 63:47
>> +Field 46 CCU
>> +Field 45:32 CC
>> +Res0 31:18
>> +Field 17 LASTFAILED
>> +Field 16 TX
>
> According to DDI0487I.a bit 16 is called T not TX.
I understand :) The intention here was to keep the field name associated with
"transaction" some how. But I guess, it would be more important to keep it as
is matching the ARM ARM than something for readability purpose. Will change it
as 'T'.
>
>> +Res0 15:14
>> +Enum 13:8 TYPE
>
> It's probably worth noting in the comment the issue with Enums here
> that's meaning you're not using a SysregFields - I'm not sure what
Sure, will add a comment describing the problem of using enum elements inside
SysregFields definition.
> people will think of this but providing a definition using the ID for
> the 0th register does seem expedient.
I understand your concern but this turned out to be a better option
- Original sysreg.h based definitions had all field masks on the right end
- When reading (reg >> field_shift) & field_mask
- When writing (val & field_mask) << field_shift
- tools/sysreg format creates in-place field masks
- When reading (reg & field_mask) >> field_shift
- When writing (val << field_shift) & field_mask
- After moving some BRBE registers into tools/sysreg, the driver code had
to be changed to accommodate these new write/read methods
- To avoid mix up in the BRBE driver, all BRBINF register fields need to be
converted into in place masks, either in sysreg.h itself or moving into
tools/sysreg
Moving BRBE fields into tools/sysreg via a dummy BRBINF_EL1 register seems
to achieve that objective. These common fields can be used to work on any
BRBINF<N>_EL1 register value. But I might just keep them in sysreg.h, if
the proposed solution is not preferable or seems expedient.
Later when enum support comes up in SysregFields and tools/sysreg supports
formula based crm/op2 expansion entire BRBINF, BRBSRC, BRBTGT register set
can be moved into tools/sysreg.
>
>> +Enum 7:6 EL
>> + 0b00 EL0
>> + 0b01 EL1
>> + 0b10 EL2
>> +EndEnum
>
> According to DDI0487I.a 0b11 has the value EL3 (when FEAT_BRBEv1p1).
Sure, will add it.
>
>> +Sysreg BRBCR_EL1 2 1 9 0 0
>> +Res0 63:24
>> +Field 23 EXCEPTION
>> +Field 22 ERTN
>> +Res0 21:9
>> +Field 8 FZP
>> +Field 7 ZERO
>
> According to DDI0487I.a bit 7 is Res0.
Sure, will change.
>
>> +Field 2 ZERO1
>
> According to DDI0487I.a bit 2 is Res0.
Sure, will change.
>
>> +Sysreg BRBFCR_EL1 2 1 9 0 1
>
>> +Field 16 ENL
>
> Accoding to DDI0487I.a this is EnI (ie, an L not an I).
ENL != Enl ? Do we need to match the case as well ?
>
>> +Sysreg BRBINFINJ_EL1 2 1 9 1 0
>
>> +Field 16 TX
>
> According to DDI0487I.a this is T not TX.
As mentioned, will change it as 'T'.
>
>> +Enum 7:6 EL
>> + 0b00 EL0
>> + 0b01 EL1
>> + 0b10 EL2
>> +EndEnum
>
> According to DDI0487I.a 0b11 has the value EL3 (when FEAT_BRBEv1p1).
Sure, will add.
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