linux-kernel - Re: [PATCH 08/10] coresight: Remove legacy Trace ID allocation mechanism

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Date:   Tue, 17 May 2022 11:56:44 +0800
From:   "liuqi (BA)" <liuqi115@...wei.com>
To:     Mike Leach <mike.leach@...aro.org>, <suzuki.poulose@....com>,
        <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <mathieu.poirier@...aro.org>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>,
        <linux-perf-users@...r.kernel.org>, <leo.yan@...aro.org>
Subject: Re: [PATCH 08/10] coresight: Remove legacy Trace ID allocation
 mechanism

Hi Mike,

On 2022/3/9 4:49, Mike Leach wrote:
> This static 'cpu * 2 + seed' was outdated and broken for systems with high
> core counts (>46).
> 
> This has been replaced by a dynamic allocation system.
> 
> Signed-off-by: Mike Leach <mike.leach@...aro.org>
> ---
>   include/linux/coresight-pmu.h | 12 ------------
>   1 file changed, 12 deletions(-)

Seems coresight_get_trace_id() in tools/include/linux/coresight-pmu.h 
need to be deleted too.

Thanks,
Qi

> 
> diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h
> index 4ac5c081af93..bb4eb4de3c77 100644
> --- a/include/linux/coresight-pmu.h
> +++ b/include/linux/coresight-pmu.h
> @@ -8,7 +8,6 @@
>   #define _LINUX_CORESIGHT_PMU_H
>   
>   #define CORESIGHT_ETM_PMU_NAME "cs_etm"
> -#define CORESIGHT_ETM_PMU_SEED  0x10
>   
>   /*
>    * Below are the definition of bit offsets for perf option, and works as
> @@ -32,15 +31,4 @@
>   #define ETM4_CFG_BIT_RETSTK	12
>   #define ETM4_CFG_BIT_VMID_OPT	15
>   
> -static inline int coresight_get_trace_id(int cpu)
> -{
> -	/*
> -	 * A trace ID of value 0 is invalid, so let's start at some
> -	 * random value that fits in 7 bits and go from there.  Since
> -	 * the common convention is to have data trace IDs be I(N) + 1,
> -	 * set instruction trace IDs as a function of the CPU number.
> -	 */
> -	return (CORESIGHT_ETM_PMU_SEED + (cpu * 2));
> -}
> -
>   #endif
>