linux-kernel - Re: [PATCH v7 2/2] fpga: dfl: fme: add performance reporting support

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Date:   Mon, 10 Feb 2020 16:34:01 +0000
From:   Will Deacon <will@...nel.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     mdf@...nel.org, mark.rutland@....com, gregkh@...uxfoundation.org,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, atull@...nel.org, yilun.xu@...el.com,
        Luwei Kang <luwei.kang@...el.com>
Subject: Re: [PATCH v7 2/2] fpga: dfl: fme: add performance reporting support

Hi,

On Mon, Feb 10, 2020 at 11:47:49AM +0800, Wu Hao wrote:
> This patch adds support for performance reporting private feature
> for FPGA Management Engine (FME). Now it supports several different
> performance counters, including 'basic', 'cache', 'fabric', 'vtd'
> and 'vtd_sip'. It allows user to use standard linux tools to access
> these performance counters.

I had a quick look at this, and it mostly looks alright to me. Just a few
high-level comments/questions:

  - I would still prefer for the PMU drivers to live under drivers/perf/

  - You should probably give the PMU a better name than "fme%d", for example
    "intel_fpga_dfl_fme%d".

  - CPU0 can be hotplugged off on non-x86 systems. How do you cope with
    that?

  - readq() will emit 2x32-bit reads on some architectures. What happens
    in this case?

Will