Re: [PATCH V7 2/6] arm64/perf: Add BRBE registers and fields

Anshuman Khandual
2023-01-13T03:04:29Z

On 1/12/23 18:54, Mark Rutland wrote:
> Hi Anshuman,
>
> On Thu, Jan 05, 2023 at 08:40:35AM +0530, Anshuman Khandual wrote:
>> This adds BRBE related register definitions and various other related field
>> macros there in. These will be used subsequently in a BRBE driver which is
>> being added later on.
>
> I haven't verified the specific values, but this looks good to me aside from
> one minor nit below.
>
> [...]
>
>> +# 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
>
> We don't need a dummy declaration, as we have 'SysregFields' that can be used
> for this, e.g.
>
> SysregFields BRBINFx_EL1
> ...
> EndSysregFields
>
> ... which will avoid accidental usage of the register encoding. Note that I've
> also added an 'x' there in place of the index, which we do for other registers,
> e.g. TTBRx_EL1.
>
> Could you please update to that?

There is a problem in defining SysregFields (which I did explore earlier as well).
SysregFields unfortunately does not support enums fields. Following build failure
comes up, while trying to convert BRBINFx_EL1 into a SysregFields definition.

Error at 932: unexpected Enum (inside SysregFields)

===============================================================================
diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
index a7f9054bd84c..519c4f080898 100644
--- a/arch/arm64/tools/sysreg
+++ b/arch/arm64/tools/sysreg
@@ -921,10 +921,7 @@ Enum 3:0 BT
EndEnum
EndSysreg

-
-# 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
+SysregFields BRBINFx_EL1
Res0 63:47
Field 46 CCU
Field 45:32 CC
@@ -967,7 +964,7 @@ Enum 1:0 VALID
0b10 SOURCE
0b11 FULL
EndEnum
-EndSysreg
+EndSysregFields

Sysreg BRBCR_EL1 2 1 9 0 0
Res0 63:24
===============================================================================

There are three enum fields in BRBINFx_EL1 as listed here.

Enum 13:8 TYPE
Enum 7:6 EL
Enum 1:0 VALID

However, BRBINF_EL1 can be changed as BRBINFx_EL1, indicating its more generic
nature with a potential to be used for any index value register thereafter.

>
> With that:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> Mark.