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SubjectRe: [PATCH v3 1/7] arm64/sysreg: Convert CCSIDR_EL1 to automatic generation
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On 2022/12/18 20:23, Marc Zyngier wrote:
> On Sun, 18 Dec 2022 05:14:06 +0000,
> Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
>>
>> Convert CCSIDR_EL1 to automatic generation as per DDI0487I.a. The field
>> definition is for case when FEAT_CCIDX is not implemented. Fields WT,
>> WB, RA and WA are defined as per A.j since they are now reserved and
>> may have UNKNOWN values in I.a, which the file format cannot represent.
>>
>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>> ---
>> arch/arm64/include/asm/sysreg.h | 1 -
>> arch/arm64/tools/sysreg | 11 +++++++++++
>> 2 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index 7d301700d1a9..910e960661d3 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -425,7 +425,6 @@
>>
>> #define SYS_CNTKCTL_EL1 sys_reg(3, 0, 14, 1, 0)
>>
>> -#define SYS_CCSIDR_EL1 sys_reg(3, 1, 0, 0, 0)
>> #define SYS_AIDR_EL1 sys_reg(3, 1, 0, 0, 7)
>>
>> #define SYS_RNDR_EL0 sys_reg(3, 3, 2, 4, 0)
>> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
>> index 384757a7eda9..acc79b5ccf92 100644
>> --- a/arch/arm64/tools/sysreg
>> +++ b/arch/arm64/tools/sysreg
>> @@ -871,6 +871,17 @@ Sysreg SCXTNUM_EL1 3 0 13 0 7
>> Field 63:0 SoftwareContextNumber
>> EndSysreg
>>
>> +Sysreg CCSIDR_EL1 3 1 0 0 0
>> +Res0 63:32
>> +Field 31:31 WT
>> +Field 30:30 WB
>> +Field 29:29 RA
>> +Field 28:28 WA
>
> For fields described as a single bit, the tool supports simply
> indicating the bit number (28 rather than 28:28).
>
> However, I strongly recommend against describing fields that have been
> dropped from the architecture. This only happens when these fields
> are never used by any implementation, so describing them is at best
> useless.

arch/arm64/tools/gen-sysreg.awk does not allow a hole and requires all
bits are described hence these descriptions. If you have an alternative
idea I'd like to hear.

>
>> +Field 27:13 NumSets
>> +Field 12:3 Associavity
>> +Field 2:0 LineSize
>> +EndSysreg
>> +
>
> I don't think we have a good solution for overlapping fields that
> depend on other factors, either contextual (such as a mode that
> changes the layout of a sysreg), or architecture warts such as
> FEAT_CCIDX (which changes the layout of a well-known sysreg).
>
> At least, put a comment here that indicates the context of the
> description.

Sounds good. I'll do so with the next version.

Regards,
Akihiko Odaki

>
> Thanks,
>
> M.
>

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