linux-kernel - Re: [PATCH v3 19/26] coresight: etm4x: Detect access early on the target CPU

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Message-ID: <20201106204649.GC3299843@xps15>
Date:   Fri, 6 Nov 2020 13:46:49 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, mike.leach@...aro.org,
        coresight@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 19/26] coresight: etm4x: Detect access early on the
 target CPU

On Wed, Oct 28, 2020 at 10:09:38PM +0000, Suzuki K Poulose wrote:
> In preparation to detect the support for system instruction
> support, move the detection of the device access to the target
> CPU.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  .../coresight/coresight-etm4x-core.c          | 45 ++++++++++++++++---
>  1 file changed, 40 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index f038bb10bc78..308674ab746c 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -56,6 +56,11 @@ static u64 etm4_get_access_type(struct etmv4_config *config);
>  
>  static enum cpuhp_state hp_online;
>  
> +struct etm_init_arg {
> +	struct etmv4_drvdata	*drvdata;
> +	struct csdev_access	*csa;
> +};
> +
>  u64 etm4x_sysreg_read(struct csdev_access *csa,
>  		      u32 offset,
>  		      bool _relaxed,
> @@ -669,6 +674,22 @@ static const struct coresight_ops etm4_cs_ops = {
>  	.source_ops	= &etm4_source_ops,
>  };
>  
> +static bool etm_init_iomem_access(struct etmv4_drvdata *drvdata,
> +				  struct csdev_access *csa)
> +{
> +	*csa = CSDEV_ACCESS_IOMEM(drvdata->base);
> +	return true;
> +}
> +
> +static bool etm_init_csdev_access(struct etmv4_drvdata *drvdata,
> +				  struct csdev_access *csa)
> +{
> +	if (drvdata->base)
> +		return etm_init_iomem_access(drvdata, csa);
> +
> +	return false;
> +}

I would also prefix the above two functions with "etm4_" rather than "etm_" to
follow what is already done in this file. 

> +
>  static void etm4_init_arch_data(void *info)
>  {
>  	u32 etmidr0;
> @@ -677,11 +698,22 @@ static void etm4_init_arch_data(void *info)
>  	u32 etmidr3;
>  	u32 etmidr4;
>  	u32 etmidr5;
> -	struct etmv4_drvdata *drvdata = info;
> -	struct csdev_access tmp_csa = CSDEV_ACCESS_IOMEM(drvdata->base);
> -	struct csdev_access *csa = &tmp_csa;
> +	struct etm_init_arg *init_arg = info;
> +	struct etmv4_drvdata *drvdata;
> +	struct csdev_access *csa;
>  	int i;
>  
> +	drvdata = init_arg->drvdata;
> +	csa = init_arg->csa;
> +
> +	/*
> +	 * If we are unable to detect the access mechanism,
> +	 * or unable to detect the trace unit type, fail
> +	 * early.
> +	 */
> +	if (!etm_init_csdev_access(drvdata, csa))
> +		return;
> +
>  	/* Make sure all registers are accessible */
>  	etm4_os_unlock_csa(drvdata, csa);
>  	etm4_cs_unlock(drvdata, csa);
> @@ -1524,6 +1556,7 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>  	struct etmv4_drvdata *drvdata;
>  	struct resource *res = &adev->res;
>  	struct coresight_desc desc = { 0 };
> +	struct etm_init_arg init_arg = { 0 };
>  
>  	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
>  	if (!drvdata)
> @@ -1551,7 +1584,6 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>  		return PTR_ERR(base);
>  
>  	drvdata->base = base;
> -	desc.access = CSDEV_ACCESS_IOMEM(base);
>  
>  	spin_lock_init(&drvdata->spinlock);
>  
> @@ -1563,8 +1595,11 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>  	if (!desc.name)
>  		return -ENOMEM;
>  
> +	init_arg.drvdata = drvdata;
> +	init_arg.csa = &desc.access;
> +
>  	if (smp_call_function_single(drvdata->cpu,
> -				etm4_init_arch_data,  drvdata, 1))
> +				etm4_init_arch_data,  &init_arg, 1))
>  		dev_err(dev, "ETM arch init failed\n");
>  
>  	if (etm4_arch_supported(drvdata->arch) == false)
> -- 
> 2.24.1
>