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To:     <suzuki.poulose@arm.com>
CC:     <yehaiyang2@hisilicon.com>, wanghuiqiang <wanghuiqiang@huawei.com>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
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        "Catalin Marinas" <catalin.marinas@arm.com>
From:   Xiongfeng Wang <wangxiongfeng2@huawei.com>
Subject: [Question] Question about supporting sysreg only CoreSight ETMv4.4 on
 ACPI machines
Message-ID: <6e85db13-a65f-d4c6-1b6b-660a94cb7060@huawei.com>
Date:   Tue, 18 Oct 2022 10:04:16 +0800
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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.

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

Thanks,
Xiongfeng