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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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