linux-kernel - Re: [PATCH 1/2] Documentation: perf: Update documentation for ThunderX2 PMU uncore driver

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Message-ID: <20190627100118.nfveq4oktomqybtx@willie-the-truck>
Date:   Thu, 27 Jun 2019 11:01:19 +0100
From:   Will Deacon <will@...nel.org>
To:     Ganapatrao Kulkarni <gkulkarni@...vell.com>
Cc:     "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Will.Deacon@....com" <Will.Deacon@....com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "corbet@....net" <corbet@....net>,
        "jnair@...iumnetworks.com" <jnair@...iumnetworks.com>,
        "Robert.Richter@...ium.com" <Robert.Richter@...ium.com>,
        "Jan.Glauber@...ium.com" <Jan.Glauber@...ium.com>,
        "gklkml16@...il.com" <gklkml16@...il.com>
Subject: Re: [PATCH 1/2] Documentation: perf: Update documentation for
 ThunderX2 PMU uncore driver

On Fri, Jun 14, 2019 at 05:42:45PM +0000, Ganapatrao Kulkarni wrote:
> From: Ganapatrao Kulkarni <ganapatrao.kulkarni@...vell.com>
> 
> Add documentation for Cavium Coherent Processor Interconnect (CCPI2) PMU.
> 
> Signed-off-by: Ganapatrao Kulkarni <gkulkarni@...vell.com>
> ---
>  Documentation/perf/thunderx2-pmu.txt | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/perf/thunderx2-pmu.txt b/Documentation/perf/thunderx2-pmu.txt
> index dffc57143736..62243230abc3 100644
> --- a/Documentation/perf/thunderx2-pmu.txt
> +++ b/Documentation/perf/thunderx2-pmu.txt
> @@ -2,24 +2,26 @@ Cavium ThunderX2 SoC Performance Monitoring Unit (PMU UNCORE)
>  =============================================================
>  
>  The ThunderX2 SoC PMU consists of independent, system-wide, per-socket
> -PMUs such as the Level 3 Cache (L3C) and DDR4 Memory Controller (DMC).
> +PMUs such as the Level 3 Cache (L3C), DDR4 Memory Controller (DMC) and
> +Cavium Coherent Processor Interconnect (CCPI2).
>  
>  The DMC has 8 interleaved channels and the L3C has 16 interleaved tiles.
>  Events are counted for the default channel (i.e. channel 0) and prorated
>  to the total number of channels/tiles.
>  
> -The DMC and L3C support up to 4 counters. Counters are independently
> -programmable and can be started and stopped individually. Each counter
> -can be set to a different event. Counters are 32-bit and do not support
> -an overflow interrupt; they are read every 2 seconds.
> +The DMC, L3C support up to 4 counters and CCPI2 support up to 8 counters.

The DMC and L3C support up to 4 counters, while the CCPI2 supports up to 8
counters.

> +Counters are independently programmable and can be started and stopped
> +individually. Each counter can be set to a different event. DMC and L3C
> +Counters are 32-bit and do not support an overflow interrupt; they are read

Counters -> counters

> +every 2 seconds. CCPI2 counters are 64-bit.

Assuming CCPI2 also doesn't support an overflow interrupt, I'd reword these
two sentences as:

  None of the counters support an overflow interrupt and therefore sampling
  events are unsupported. The DMC and L3C counters are 32-bit and read every
  2 seconds. The CCPI2 counters are 64-bit and assumed not to overflow in
  normal operation.

>  PMU UNCORE (perf) driver:
>  
>  The thunderx2_pmu driver registers per-socket perf PMUs for the DMC and
> -L3C devices.  Each PMU can be used to count up to 4 events
> -simultaneously. The PMUs provide a description of their available events
> -and configuration options under sysfs, see
> -/sys/devices/uncore_<l3c_S/dmc_S/>; S is the socket id.
> +L3C devices.  Each PMU can be used to count up to 4(DMC/L3C) or up to 8

Space between 4 and (

Will