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Subject: Re: [Question] Question about supporting sysreg only CoreSight
 ETMv4.4 on ACPI machines
To:     Suzuki Kuruppassery Poulose <suzuki.poulose@arm.com>
CC:     <yehaiyang2@hisilicon.com>, wanghuiqiang <wanghuiqiang@huawei.com>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>, <mark.rutland@arm.com>,
        "Catalin Marinas" <catalin.marinas@arm.com>,
        Anshuman Khandual <Anshuman.Khandual@arm.com>
References: <6e85db13-a65f-d4c6-1b6b-660a94cb7060@huawei.com>
 <9fc5ab20-c7f0-a917-4938-403e3661109f@arm.com>
From:   Xiongfeng Wang <wangxiongfeng2@huawei.com>
Message-ID: <5c4d3a7f-0dcb-c0e9-0192-2a53d0338078@huawei.com>
Date:   Wed, 19 Oct 2022 10:04:31 +0800
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Hi, Suzuki, Anshuman

On 2022/10/18 17:18, Suzuki Kuruppassery Poulose wrote:
> Hi,
> 
> Cc: Anshuman
> 
> On 18/10/2022 03:04, Xiongfeng Wang wrote:
>> Hi, Suzuki
>>
>>     We are testing CoreSight ETMv4.4 and TRBE recently. ETMv4.4 obsoletes memory
>> mapped access to ETM and mandates the system registers. The following commit add
>> driver for sysreg only devices, but it only support device tree.
>>    commit 5214b563588e8414193bd7a174c52350256942a6
>>    coresight: etm4x: Add support for sysreg only devices
>>
>> ACPI machine can use 'ARMHC500' to report a ETM4x device. But the corresponding
>> driver is etm4x_amba_driver. It needs memory resouces and doesn't support sysreg
>> only device.
> 
> That is true. Unfortunately, supporting this requires us to move away from the
> AMBA framework (at least) for ETM4x devices. This is currently
> developed by Anshuman. We can share it as soon as this is complete.

Thanks a lot. Really appreciate !
By the way, do we have plan to add ACPI support for TRBE driver? ACPI 6.5 add a
field 'TRBE Interrupt' in GICC Structure. In the beginning, I plan to add a
platform device when got this IRQ, just like what SPE does in the following commit
  commit d24a0c7099b32b6981d7f126c45348e381718350
  arm_pmu: acpi: spe: Add initial MADT/SPE probing
But it seems that TRBE still needs _DSD method to report the links(input port
and output port). Do you have some other advices? Thanks a lot.

Thanks
Xiongfeng

> 
> Thanks
> Suzuki
> 
>>
>> Do we have some other way to use CoreSight ETMv4.4 on ACPI machines. Thanks a
>> lot.
>>
>> Thanks,
>> Xiongfeng
> 
> 
> .