linux-kernel - Re: [PATCH 14/17] fpga: dfl: fme: add thermal management support

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Date:   Tue, 2 Apr 2019 07:59:25 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     atull@...nel.org, mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Luwei Kang <luwei.kang@...el.com>,
        Russ Weight <russell.h.weight@...el.com>,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH 14/17] fpga: dfl: fme: add thermal management support

Hi Wu,

On Mon, Mar 25, 2019 at 11:07:41AM +0800, Wu Hao wrote:
> This patch adds support to thermal management private feature for DFL
> FPGA Management Engine (FME). As thermal throttling is handled by
> hardware automatically per pre-defined thresholds, this private
> feature driver only provides read-only sysfs interfaces for user
> to read temperature, thresholds, threshold policy and other info.
> 
> Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> Signed-off-by: Wu Hao <hao.wu@...el.com>
> ---
>  Documentation/ABI/testing/sysfs-platform-dfl-fme |  56 +++++++
>  drivers/fpga/dfl-fme-main.c                      | 202 +++++++++++++++++++++++
>  2 files changed, 258 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-platform-dfl-fme b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> index b8327e9..d3aeb88 100644
> --- a/Documentation/ABI/testing/sysfs-platform-dfl-fme
> +++ b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> @@ -44,3 +44,59 @@ Description:	Read-only. It returns socket_id to indicate which socket
>  		this FPGA belongs to, only valid for integrated solution.
>  		User only needs this information, in case standard numa node
>  		can't provide correct information.
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/temperature
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. It returns temperature (in Celsius) of this FPGA
> +		device.
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. Read this file to get the temperature threshold1
> +		(in Celsius).
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold2
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. Read this file to get the temperature threshold2
> +		(in Celsius).
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/trip_threshold
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. It returns trip threshold (in Celsius), once FPGA
> +		temperature reaches trip threshold, it triggers a fatal event
> +		to board management controller (BMC) to shutdown FPGA.
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1_status
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. It returns 1 if temperature reaches threshold1,
> +		otherwise 0. Once temperature reaches threshold1, hardware
> +		will automatically enter throttling state (AP1 - 50%
> +		or AP2 - 90% throttling, see 'threshold1_policy').
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold2_status
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. It returns 1 if temperature reaches threshold2,
> +		otherwise 0. Once temperature reaches threshold2, hardware
> +		will automatically enter the deepest throttling state (AP6
> +		- 100% throttling).
> +
> +What:		/sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1_policy
> +Date:		March 2019
> +KernelVersion:  5.2
> +Contact:	Wu Hao <hao.wu@...el.com>
> +Description:	Read-only. Read this file to get the policy of temperature
> +		threshold1. It only supports two value (policy):
> +		    0 - AP2 state (90% throttling)
> +		    1 - AP1 state (50% throttling)

These look like they could directly map to the linux thermal framework,
any reason you can't use the thermal framework?

The trip stuff literally maps 1:1 to what a thermal driver does, I think
that's something you'd wanna consider.

Cheers,
Moritz