Re: [PATCH 05/11] drivers: bus: add the stm32 debug bus driver

On 1/11/26 12:27, Krzysztof Kozlowski wrote:

On 09/01/2026 11:55, Gatien Chevallier wrote:

quoted

Add the stm32 debug bus driver that is responsible of checking the
+
+static int stm32_dbg_bus_grant_access(struct stm32_firewall_controller *ctrl, u32 dbg_profile)
+{
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[1] = {0};
+	u32 session_id;
+	int ret;
+
+	if (dbg_profile != PERIPHERAL_DBG_PROFILE && dbg_profile != HDP_DBG_PROFILE)
+		return -EOPNOTSUPP;
+
+	ret = stm32_dbg_pta_open_session(&session_id);
+	if (ret)
+		return ret;
+
+	inv_arg.func = PTA_CMD_GRANT_DBG_ACCESS;
+	inv_arg.session = session_id;
+	inv_arg.num_params = 1;
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT;
+	param[0].u.value.a = dbg_profile;
+
+	ret = tee_client_invoke_func(stm32_dbg_bus_priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0) {
+		dev_dbg(stm32_dbg_bus_priv->dev,
+			"When invoking function, err %x, TEE returns: %x\n", ret, inv_arg.ret);
+		if (!ret)
+			ret = -EACCES;
+	}
+
+	stm32_dbg_pta_close_session(session_id);
+
+	return ret;
+}
+
+/* Implement mandatory release_access ops even if it does nothing*/
+static void stm32_dbg_bus_release_access(struct stm32_firewall_controller *ctrl, u32 dbg_profile)
+{
+}
+
+static int stm32_dbg_bus_plat_probe(struct platform_device *pdev)
+{
+	struct stm32_firewall_controller *dbg_controller;
+	int ret;
+
+	if (!stm32_dbg_bus_priv)
+		return dev_err_probe(&pdev->dev, -EPROBE_DEFER,
+				     "OP-TEE debug services not yet available\n");
+
+	dbg_controller = devm_kzalloc(&pdev->dev, sizeof(*dbg_controller), GFP_KERNEL);
+	if (!dbg_controller)
+		return dev_err_probe(&pdev->dev, -ENOMEM, "Couldn't allocate debug controller\n");
+
+	dbg_controller->dev = &pdev->dev;
+	dbg_controller->mmio = NULL;
+	dbg_controller->name = dev_driver_string(dbg_controller->dev);
+	dbg_controller->type = STM32_PERIPHERAL_FIREWALL;
+	dbg_controller->grant_access = stm32_dbg_bus_grant_access;
+	dbg_controller->release_access = stm32_dbg_bus_release_access;
+
+	stm32_dbg_bus_priv->dbg_clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(stm32_dbg_bus_priv->dbg_clk))
+		return PTR_ERR(stm32_dbg_bus_priv->dbg_clk);
+
+	ret = stm32_firewall_controller_register(dbg_controller);
+	if (ret) {
+		dev_err(dbg_controller->dev, "Couldn't register as a firewall controller: %d", ret);
+		return ret;
+	}
+
+	ret = stm32_firewall_populate_bus(dbg_controller);
+	if (ret) {
+		dev_err(dbg_controller->dev, "Couldn't populate debug bus: %d", ret);
+		stm32_firewall_controller_unregister(dbg_controller);
+		return ret;
+	}
+
+	pm_runtime_enable(&pdev->dev);
+
+	ret = of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
+	if (ret) {
+		dev_err(dbg_controller->dev, "Couldn't populate the node: %d", ret);
+		stm32_firewall_controller_unregister(dbg_controller);
+		return ret;

Where do you depopulate on unbind?

Nowhere, so I'll add it for V2.

quoted

+	}
+
+	return 0;
+}
+
+static int __maybe_unused stm32_dbg_bus_runtime_suspend(struct device *dev)
+{
+	clk_disable_unprepare(stm32_dbg_bus_priv->dbg_clk);
+
+	return 0;
+}
+
+static int __maybe_unused stm32_dbg_bus_runtime_resume(struct device *dev)
+{
+	int ret = clk_prepare_enable(stm32_dbg_bus_priv->dbg_clk);
+
+	if (ret) {
+		dev_err(dev, "Failed to enable clock: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id stm32_dbg_bus_of_match[] = {
+	{ .compatible = "st,stm32mp131-dbg-bus", },
+	{ .compatible = "st,stm32mp151-dbg-bus", },

So devices are fully compatible?

As it is a standard bus, yes. The goal of this driver is to be
able to interface with the secure world to check the debug
configuration.

quoted

+	{ },
+};
+MODULE_DEVICE_TABLE(of, stm32_dbg_bus_of_match);
+
+static const struct dev_pm_ops simple_pm_bus_pm_ops = {
+	SET_RUNTIME_PM_OPS(stm32_dbg_bus_runtime_suspend, stm32_dbg_bus_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+};
+
+static struct platform_driver stm32_dbg_bus_driver = {
+	.probe = stm32_dbg_bus_plat_probe,
+	.driver = {
+		.name = "stm32-dbg-bus",
+		.of_match_table = of_match_ptr(stm32_dbg_bus_of_match),

Warning :/. Why do people still keep copying of_match_ptr?

I'll remove that in V2.

quoted

+		.pm = pm_ptr(&simple_pm_bus_pm_ops),
+	},
+};
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	return (ver->impl_id == TEE_IMPL_ID_OPTEE);
+}
+
+static int stm32_dbg_bus_probe(struct device *dev)
+{
+	struct stm32_dbg_bus *priv;
+
+	if (stm32_dbg_bus_priv)
+		return dev_err_probe(dev, -EBUSY,
+				     "A STM32 debug bus device is already initialized\n");
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return dev_err_probe(dev, -ENOMEM, "Cannot allocate priv data\n");

You NEVER print error allocations on kzalloc, even if with dev_err_probe
it is silenced.

Ok, I'll keep that in mind and remove that for V2.

Best regards,
Gatien

quoted

+
+	/* Open context with TEE driver */
+	priv->ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
+	if (IS_ERR_OR_NULL(priv->ctx))
+		return dev_err_probe(dev, PTR_ERR_OR_ZERO(priv->ctx), "Cannot open TEE context\n");
+
+	stm32_dbg_bus_priv = priv;
+	stm32_dbg_bus_priv->dev = dev;
+
+	return 0;
+}
+
+static int stm32_dbg_bus_remove(struct device *dev)
+{
+	tee_client_close_context(stm32_dbg_bus_priv->ctx);
+	stm32_dbg_bus_priv = NULL;
+
+	return 0;
+}
+
+static const struct tee_client_device_id optee_dbg_bus_id_table[] = {
+	{UUID_INIT(0xdd05bc8b, 0x9f3b, 0x49f0,
+		   0xb6, 0x49, 0x01, 0xaa, 0x10, 0xc1, 0xc2, 0x10)},
+	{}
+};
+
+static struct tee_client_driver stm32_optee_dbg_bus_driver = {
+	.id_table = optee_dbg_bus_id_table,
+	.driver = {
+		.name = "optee_dbg_bus",
+		.bus = &tee_bus_type,
+		.probe = stm32_dbg_bus_probe,
+		.remove = stm32_dbg_bus_remove,
+	},
+};
+
+static int __init optee_dbg_bus_mod_init(void)
+{
+	int ret;
+
+	ret = driver_register(&stm32_optee_dbg_bus_driver.driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&stm32_dbg_bus_driver);
+	if (ret)
+		driver_unregister(&stm32_optee_dbg_bus_driver.driver);
+
+	return ret;
+}
+
+static void __exit optee_dbg_bus_mod_exit(void)
+{
+	platform_driver_unregister(&stm32_dbg_bus_driver);
+	driver_unregister(&stm32_optee_dbg_bus_driver.driver);
+}
+
+module_init(optee_dbg_bus_mod_init);
+module_exit(optee_dbg_bus_mod_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Gatien Chevallier [off-list ref]");
+MODULE_DESCRIPTION("OP-TEE based STM32 debug access bus driver");

Best regards,
Krzysztof