linux-kernel - Re: [PATCH v6 22/26] coresight: etm4x: Run arch feature detection on the CPU

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Message-ID: <20210108004946.GF43045@xps15>
Date:   Thu, 7 Jan 2021 17:49:46 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, leo.yan@...aro.org,
        mike.leach@...aro.org, anshuman.khandual@....com,
        liuqi115@...wei.com
Subject: Re: [PATCH v6 22/26] coresight: etm4x: Run arch feature detection on
 the CPU

On Thu, Jan 07, 2021 at 12:38:55PM +0000, Suzuki K Poulose wrote:
> As we are about to add support for system register based devices,
> we don't get an AMBA pid. So, the detection code could check
> the system registers running on the CPU to check for the architecture
> specific features. Thus we move the arch feature detection to
> run on the CPU. We cannot always read the PID from the HW (i.e even
> for AMBA devices), as the as the PID could be overridden by DT for

s/as the as the/as the

I made the change.

> broken devices. So, use the PID from AMBA layer if available.
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: liuqi115@...wei.com
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x-core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 228845f6fdd8..f4fbb65b4cc1 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -60,6 +60,7 @@ static u64 etm4_get_access_type(struct etmv4_config *config);
>  static enum cpuhp_state hp_online;
>  
>  struct etm4_init_arg {
> +	unsigned int		pid;
>  	struct etmv4_drvdata	*drvdata;
>  	struct csdev_access	*csa;
>  };
> @@ -884,6 +885,8 @@ static void etm4_init_arch_data(void *info)
>  	etm4_os_unlock_csa(drvdata, csa);
>  	etm4_cs_unlock(drvdata, csa);
>  
> +	etm4_check_arch_features(drvdata, init_arg->pid);
> +
>  	/* find all capabilities of the tracing unit */
>  	etmidr0 = etm4x_relaxed_read32(csa, TRCIDR0);
>  
> @@ -1750,6 +1753,7 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
>  
>  	init_arg.drvdata = drvdata;
>  	init_arg.csa = &desc.access;
> +	init_arg.pid = etm_pid;
>  
>  	if (smp_call_function_single(drvdata->cpu,
>  				etm4_init_arch_data,  &init_arg, 1))
> @@ -1794,8 +1798,6 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
>  		drvdata->boot_enable = true;
>  	}
>  
> -	etm4_check_arch_features(drvdata, etm_pid);
> -
>  	return 0;
>  }
>  
> -- 
> 2.24.1
>