firmware: scmi: sandbox test for SCMI clocks

Add tests for SCMI clocks. A test device driver sandbox-scmi_devices.c
is used to get clock resources, allowing further clock manipulation.

Change sandbox-smci_agent to emulate 3 clocks exposed through 2 agents.
Add DM test scmi_clocks to test these 3 clocks.
Update DM test sandbox_scmi_agent with load/remove test sequences
factorized by {load|remove}_sandbox_scmi_test_devices() helper functions.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/firmware/scmi/sandbox-scmi_devices.c b/drivers/firmware/scmi/sandbox-scmi_devices.c
new file mode 100644
index 0000000..b3e411c
--- /dev/null
+++ b/drivers/firmware/scmi/sandbox-scmi_devices.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020, Linaro Limited
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <malloc.h>
+#include <asm/io.h>
+#include <asm/scmi_test.h>
+#include <dm/device_compat.h>
+
+/*
+ * Simulate to some extent a SCMI exchange.
+ * This drivers gets SCMI resources and offers API function to the
+ * SCMI test sequence manipulate the resources, currently clocks.
+ */
+
+#define SCMI_TEST_DEVICES_CLK_COUNT		3
+
+/*
+ * struct sandbox_scmi_device_priv - Storage for device handles used by test
+ * @clk:		Array of clock instances used by tests
+ * @devices:		Resources exposed by sandbox_scmi_devices_ctx()
+ */
+struct sandbox_scmi_device_priv {
+	struct clk clk[SCMI_TEST_DEVICES_CLK_COUNT];
+	struct sandbox_scmi_devices devices;
+};
+
+struct sandbox_scmi_devices *sandbox_scmi_devices_ctx(struct udevice *dev)
+{
+	struct sandbox_scmi_device_priv *priv = dev_get_priv(dev);
+
+	if (priv)
+		return &priv->devices;
+
+	return NULL;
+}
+
+static int sandbox_scmi_devices_probe(struct udevice *dev)
+{
+	struct sandbox_scmi_device_priv *priv = dev_get_priv(dev);
+	int ret;
+	size_t n;
+
+	priv->devices = (struct sandbox_scmi_devices){
+		.clk = priv->clk,
+		.clk_count = SCMI_TEST_DEVICES_CLK_COUNT,
+	};
+
+	for (n = 0; n < SCMI_TEST_DEVICES_CLK_COUNT; n++) {
+		ret = clk_get_by_index(dev, n, priv->devices.clk + n);
+		if (ret) {
+			dev_err(dev, "%s: Failed on clk %zu\n", __func__, n);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static const struct udevice_id sandbox_scmi_devices_ids[] = {
+	{ .compatible = "sandbox,scmi-devices" },
+	{ }
+};
+
+U_BOOT_DRIVER(sandbox_scmi_devices) = {
+	.name = "sandbox-scmi_devices",
+	.id = UCLASS_MISC,
+	.of_match = sandbox_scmi_devices_ids,
+	.priv_auto_alloc_size = sizeof(struct sandbox_scmi_device_priv),
+	.probe = sandbox_scmi_devices_probe,
+};