[PATCH v6 23/26] coresight: etm4x: Add support for sysreg only devices

[Suzuki K Poulose]

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.le...@linaro.org>
Cc: Mathieu Poirier <mathieu.poir...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.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);
        etm4_pm_clear();
 }
 
-- 
2.24.1