linux-kernel - Re: [PATCH v6 26/26] coresight: Add support for v8.4 SelfHosted tracing

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Message-ID: <20210108010238.GI43045@xps15>
Date:   Thu, 7 Jan 2021 18:02:38 -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,
        Jonathan Zhou <jonathan.zhouwen@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v6 26/26] coresight: Add support for v8.4 SelfHosted
 tracing

On Thu, Jan 07, 2021 at 12:38:59PM +0000, Suzuki K Poulose wrote:
> From: Jonathan Zhou <jonathan.zhouwen@...wei.com>
> 
> v8.4 tracing extensions added support for trace filtering controlled
> by TRFCR_ELx. This must be programmed to allow tracing at EL1/EL2 and
> EL0. The timestamp used is the virtual time. Also enable CONTEXIDR_EL2
> tracing if we are running the kernel at EL2.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Will Deacon <will@...nel.org>
> Signed-off-by: Jonathan Zhou <jonathan.zhouwen@...wei.com>
> [ Move the trace filtering setup etm_init_arch_data() and
>  clean ups]
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

> ---
>  .../coresight/coresight-etm4x-core.c          | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 34a6cdff75e7..6d96f4226bca 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -859,6 +859,30 @@ static bool etm4_init_csdev_access(struct etmv4_drvdata *drvdata,
>  	return false;
>  }
>  
> +static void cpu_enable_tracing(void)
> +{
> +	u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
> +	u64 trfcr;
> +
> +	if (!cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRACE_FILT_SHIFT))
> +		return;
> +
> +	/*
> +	 * If the CPU supports v8.4 SelfHosted Tracing, enable
> +	 * tracing at the kernel EL and EL0, forcing to use the
> +	 * virtual time as the timestamp.
> +	 */
> +	trfcr = (TRFCR_ELx_TS_VIRTUAL |
> +		 TRFCR_ELx_ExTRE |
> +		 TRFCR_ELx_E0TRE);
> +
> +	/* If we are running at EL2, allow tracing the CONTEXTIDR_EL2. */
> +	if (is_kernel_in_hyp_mode())
> +		trfcr |= TRFCR_EL2_CX;
> +
> +	write_sysreg_s(trfcr, SYS_TRFCR_EL1);
> +}
> +
>  static void etm4_init_arch_data(void *info)
>  {
>  	u32 etmidr0;
> @@ -1044,6 +1068,7 @@ static void etm4_init_arch_data(void *info)
>  	/* NUMCNTR, bits[30:28] number of counters available for tracing */
>  	drvdata->nr_cntr = BMVAL(etmidr5, 28, 30);
>  	etm4_cs_lock(drvdata, csa);
> +	cpu_enable_tracing();
>  }
>  
>  static inline u32 etm4_get_victlr_access_type(struct etmv4_config *config)
> -- 
> 2.24.1
>