linux-kernel - Re: [PATCH v4 00/30] coresight: Support for ACPI bindings

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Message-ID: <b45be0f7-5573-23fb-90c1-9a8e4fc6a5e1@arm.com>
Date:   Thu, 23 May 2019 14:37:55 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
        coresight@...ts.linaro.org
Subject: Re: [PATCH v4 00/30] coresight: Support for ACPI bindings



On 22/05/2019 11:34, Suzuki K Poulose wrote:
> This series adds the support for CoreSight devices on ACPI based
> platforms. The device connections are encoded as _DSD graph property[0],
> with CoreSight specific extensions to indicate the direction of data
> flow as described in [1]. Components attached to CPUs are listed
> as child devices of the corresponding CPU, removing explicit links
> to the CPU like we do in the DT.
> 
> The majority of the series cleans up the driver and prepares the subsystem
> for platform agnostic firwmare probing, naming scheme, searching etc.
> 
> We introduce platform independent helpers to parse the platform supplied
> information. Thus we rename the platform handling code from:
> 	of_coresight.c  => coresight-platform.c
> 
> The CoreSight driver creates shadow devices that appear on the Coresight
> bus, in addition to the real devices (e.g, AMBA bus devices). The name
> of these devices match the real device. This makes the device name
> a bit cryptic for ACPI platform. So this series also introduces a generic
> platform agnostic device naming scheme for the shadow Coresight devices.
> Towards this we also make changes to the way we lookup devices to resolve
> the connections, as we can't use the names to identify the devices. So,
> we use the "fwnode_handle" of the real device for the device lookups.
> Towards that we clean up the drivers to keep track of the "CoreSight"
> device rather than the "real" device. However, all real operations,
> like DMA allocation, Power management etc. must be performed on
> the real device which is the parent of the shadow device.
> 
> Finally we add the support for parsing the ACPI platform data. The power
> management support is missing in the ACPI (and this is not specific to
> CoreSight). The firmware must ensure that the respective power domains
> are turned on.
> 
> Applies on v5.2-rc1
> 
> Tested on a Juno-r0 board with ACPI bindings patch (Patch 31/30) added on
> top of [2]. You would need to make sure that the debug power domain is
> turned on before the Linux kernel boots. (e.g, connect the DS-5 to the
> Juno board while at UEFI). arm32 code is only compile tested.
> 
> [0] ACPI Device Graphs using _DSD (Not available online yet, approved but
>      awaiting publish and eventually should be linked at).
>      https://uefi.org/sites/default/files/resources/_DSD-implementation-guide-toplevel-1_1.htm
> [1] https://developer.arm.com/docs/den0067/latest/acpi-for-coresighttm-10-platform-design-document
> [2] https://github.com/tianocore/edk2-platforms.git

The kernel patches are also available at :

git://linux-arm.org/linux-skp.git coresight-acpi/v4

Suzuki