linux-kernel - Re: [PATCH v4 09/19] coresight: etm4x: Move ETM to prohibited region for disable

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Date:   Tue, 16 Mar 2021 13:30:08 -0600
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,
        mike.leach@...aro.org, anshuman.khandual@....com,
        leo.yan@...aro.org
Subject: Re: [PATCH v4 09/19] coresight: etm4x: Move ETM to prohibited region
 for disable

On Thu, Feb 25, 2021 at 07:35:33PM +0000, Suzuki K Poulose wrote:
> If the CPU implements Arm v8.4 Trace filter controls (FEAT_TRF),
> move the ETM to trace prohibited region using TRFCR, while disabling.
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> New patch

I would ask you to refrain from introducing new patches.  Otherwise the goal
posts keep on moving with every revision and we'll never get through.  Fixes and
enhancement can come in later patchsets.  

> ---
>  .../coresight/coresight-etm4x-core.c          | 21 +++++++++++++++++--
>  drivers/hwtracing/coresight/coresight-etm4x.h |  2 ++
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 15016f757828..00297906669c 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -31,6 +31,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/property.h>
>  
> +#include <asm/barrier.h>
>  #include <asm/sections.h>
>  #include <asm/sysreg.h>
>  #include <asm/local.h>
> @@ -654,6 +655,7 @@ static int etm4_enable(struct coresight_device *csdev,
>  static void etm4_disable_hw(void *info)
>  {
>  	u32 control;
> +	u64 trfcr;
>  	struct etmv4_drvdata *drvdata = info;
>  	struct etmv4_config *config = &drvdata->config;
>  	struct coresight_device *csdev = drvdata->csdev;
> @@ -676,6 +678,16 @@ static void etm4_disable_hw(void *info)
>  	/* EN, bit[0] Trace unit enable bit */
>  	control &= ~0x1;
>  
> +	/*
> +	 * If the CPU supports v8.4 Trace filter Control,
> +	 * set the ETM to trace prohibited region.
> +	 */
> +	if (drvdata->trfc) {
> +		trfcr = read_sysreg_s(SYS_TRFCR_EL1);
> +		write_sysreg_s(trfcr & ~(TRFCR_ELx_ExTRE | TRFCR_ELx_E0TRE),
> +			       SYS_TRFCR_EL1);
> +		isb();
> +	}
>  	/*
>  	 * Make sure everything completes before disabling, as recommended
>  	 * by section 7.3.77 ("TRCVICTLR, ViewInst Main Control Register,
> @@ -683,12 +695,16 @@ static void etm4_disable_hw(void *info)
>  	 */
>  	dsb(sy);
>  	isb();
> +	/* Trace synchronization barrier, is a nop if not supported */
> +	tsb_csync();
>  	etm4x_relaxed_write32(csa, control, TRCPRGCTLR);
>  
>  	/* wait for TRCSTATR.PMSTABLE to go to '1' */
>  	if (coresight_timeout(csa, TRCSTATR, TRCSTATR_PMSTABLE_BIT, 1))
>  		dev_err(etm_dev,
>  			"timeout while waiting for PM stable Trace Status\n");
> +	if (drvdata->trfc)
> +		write_sysreg_s(trfcr, SYS_TRFCR_EL1);

drvdata->trfc is invariably set to true in cpu_enable_tracing() and as such
testing for it is not required. 

>  
>  	/* read the status of the single shot comparators */
>  	for (i = 0; i < drvdata->nr_ss_cmp; i++) {
> @@ -873,7 +889,7 @@ static bool etm4_init_csdev_access(struct etmv4_drvdata *drvdata,
>  	return false;
>  }
>  
> -static void cpu_enable_tracing(void)
> +static void cpu_enable_tracing(struct etmv4_drvdata *drvdata)
>  {
>  	u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
>  	u64 trfcr;
> @@ -881,6 +897,7 @@ static void cpu_enable_tracing(void)
>  	if (!cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRACE_FILT_SHIFT))
>  		return;
>  
> +	drvdata->trfc = true;
>  	/*
>  	 * If the CPU supports v8.4 SelfHosted Tracing, enable
>  	 * tracing at the kernel EL and EL0, forcing to use the
> @@ -1082,7 +1099,7 @@ 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();
> +	cpu_enable_tracing(drvdata);

At least for this patch, the above three hunks aren't needed.

>  }
>  
>  static inline u32 etm4_get_victlr_access_type(struct etmv4_config *config)
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 0af60571aa23..f6478ef642bf 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -862,6 +862,7 @@ struct etmv4_save_state {
>   * @nooverflow:	Indicate if overflow prevention is supported.
>   * @atbtrig:	If the implementation can support ATB triggers
>   * @lpoverride:	If the implementation can support low-power state over.
> + * @trfc:	If the implementation supports Arm v8.4 trace filter controls.
>   * @config:	structure holding configuration parameters.
>   * @save_state:	State to be preserved across power loss
>   * @state_needs_restore: True when there is context to restore after PM exit
> @@ -912,6 +913,7 @@ struct etmv4_drvdata {
>  	bool				nooverflow;
>  	bool				atbtrig;
>  	bool				lpoverride;
> +	bool				trfc;

Nor is this one.  

>  	struct etmv4_config		config;
>  	struct etmv4_save_state		*save_state;
>  	bool				state_needs_restore;
> -- 
> 2.24.1
>