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Date:   Thu, 7 Jan 2021 17:55:30 -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
Subject: Re: [PATCH v6 23/26] coresight: etm4x: Add support for sysreg only
 devices

On Thu, Jan 07, 2021 at 12:38:56PM +0000, Suzuki K Poulose wrote:
> Add support for devices with system instruction access only.
> They don't have a memory mapped interface and thus are not
> AMBA devices. System register access is not permitted to
> TRCPDCR and thus skip access to them.
> 
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes since v5:
>  - Rebased to accommodate check_arch_features().
>    Added comments to explain why we don't pass PID for system
>    register based devices.
> Changes since v4
>  - Add "remove" callback for platform_driver.
>  - Dropped Reviewed-by tag from Mathieu due to the above
> 
> Changes since v3
>  - Improve comment over "TRCPDCR" usage with sysreg
>  - Rename etm_xx => etm4_xx
>  - Update the compatible to "arm,coresight-etm4x-sysreg"
> ---
>  .../coresight/coresight-etm4x-core.c          | 68 +++++++++++++++++--
>  1 file changed, 63 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index f4fbb65b4cc1..34a6cdff75e7 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -27,6 +27,7 @@
>  #include <linux/seq_file.h>
>  #include <linux/uaccess.h>
>  #include <linux/perf_event.h>
> +#include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/property.h>
>  
> @@ -1736,9 +1737,6 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
>  			return -ENOMEM;
>  	}
>  
> -	if (fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up"))
> -		drvdata->skip_power_up = true;
> -
>  	drvdata->base = base;
>  
>  	spin_lock_init(&drvdata->spinlock);
> @@ -1762,6 +1760,11 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
>  	if (!drvdata->arch)
>  		return -EINVAL;
>  
> +	/* TRCPDCR is not accessible with system instructions. */
> +	if (!desc.access.io_mem ||
> +	    fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up"))
> +		drvdata->skip_power_up = true;
> +
>  	etm4_init_trace_id(drvdata);
>  	etm4_set_default(&drvdata->config);
>  
> @@ -1820,6 +1823,25 @@ static int etm4_probe_amba(struct amba_device *adev, const struct amba_id *id)
>  	return ret;
>  }
>  
> +static int etm4_probe_platform_dev(struct platform_device *pdev)
> +{
> +	int ret;
> +
> +	pm_runtime_get_noresume(&pdev->dev);
> +	pm_runtime_set_active(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);
> +
> +	/*
> +	 * System register based devices could match the
> +	 * HW by reading appropriate registers on the HW
> +	 * and thus we could skip the PID.
> +	 */
> +	ret = etm4_probe(&pdev->dev, NULL, 0);
> +
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
>  static struct amba_cs_uci_id uci_id_etm4[] = {
>  	{
>  		/*  ETMv4 UCI data */
> @@ -1869,6 +1891,17 @@ static int __exit etm4_remove_amba(struct amba_device *adev)
>  	return 0;
>  }
>  
> +static int __exit etm4_remove_platform_dev(struct platform_device *pdev)
> +{
> +	int ret = 0;
> +	struct etmv4_drvdata *drvdata = dev_get_drvdata(&pdev->dev);
> +
> +	if (drvdata)
> +		ret = etm4_remove_dev(drvdata);
> +	pm_runtime_disable(&pdev->dev);
> +	return ret;
> +}
> +
>  static const struct amba_id etm4_ids[] = {
>  	CS_AMBA_ID(0x000bb95d),			/* Cortex-A53 */
>  	CS_AMBA_ID(0x000bb95e),			/* Cortex-A57 */
> @@ -1901,6 +1934,21 @@ static struct amba_driver etm4x_amba_driver = {
>  	.id_table	= etm4_ids,
>  };
>  
> +static const struct of_device_id etm4_sysreg_match[] = {
> +	{ .compatible	= "arm,coresight-etm4x-sysreg" },
> +	{}
> +};
> +
> +static struct platform_driver etm4_platform_driver = {
> +	.probe		= etm4_probe_platform_dev,
> +	.remove		= etm4_remove_platform_dev,
> +	.driver			= {
> +		.name			= "coresight-etm4x",
> +		.of_match_table		= etm4_sysreg_match,
> +		.suppress_bind_attrs	= true,
> +	},
> +};
> +
>  static int __init etm4x_init(void)
>  {
>  	int ret;
> @@ -1913,16 +1961,26 @@ static int __init etm4x_init(void)
>  
>  	ret = amba_driver_register(&etm4x_amba_driver);
>  	if (ret) {
> -		pr_err("Error registering etm4x driver\n");
> -		etm4_pm_clear();
> +		pr_err("Error registering etm4x AMBA driver\n");
> +		goto clear_pm;
>  	}
>  
> +	ret = platform_driver_register(&etm4_platform_driver);
> +	if (!ret)
> +		return 0;
> +
> +	pr_err("Error registering etm4x platform driver\n");
> +	amba_driver_unregister(&etm4x_amba_driver);
> +
> +clear_pm:
> +	etm4_pm_clear();
>  	return ret;
>  }
>  
>  static void __exit etm4x_exit(void)
>  {
>  	amba_driver_unregister(&etm4x_amba_driver);
> +	platform_driver_unregister(&etm4_platform_driver);

Good catch.

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

>  	etm4_pm_clear();
>  }
>  
> -- 
> 2.24.1
> 

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