drivers: aon: Add AON Echo driver

Add AON echo driver. This driver creates data_channel file in sysfs
which is used to communicate between CCPLEX and AON.

Bug 4296173

Change-Id: Id790fc4076205e16509611f7fa07ffc073491227
Signed-off-by: Gautham Srinivasan <gauthams@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/2954202
(cherry picked from commit 66c26d1ac3)
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3015993
Reviewed-by: Amulya Yarlagadda <ayarlagadda@nvidia.com>
Tested-by: Amulya Yarlagadda <ayarlagadda@nvidia.com>

drivers/platform/tegra/aon/Makefile

@@ -10,6 +10,7 @@ LINUXINCLUDE += -I$(srctree.nvidia-oot)/drivers/platform/tegra/aon/include
 ccflags-y += -Werror
 
 obj-m += tegra234-aon.o
+obj-m += tegra-aon-ivc-echo.o
 
 tegra234-aon-objs += \
     tegra-aon-hsp.o \

drivers/platform/tegra/aon/tegra-aon-ivc-echo.c

@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// SPDX-FileCopyrightText: Copyright (c) 2017-2023, NVIDIA CORPORATION & AFFILIATES.  All rights reserved.
+
+#include <linux/device.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/tegra-aon.h>
+
+#define TX_BLOCK_PERIOD	100
+#define IVC_FRAME_SIZE	64
+
+struct tegra_aon_ivc_echo_data {
+	struct mbox_client cl;
+	struct mbox_chan *mbox;
+	char rx_data[IVC_FRAME_SIZE];
+};
+
+static ssize_t tegra_aon_ivc_echo_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct tegra_aon_ivc_echo_data *drvdata = dev_get_drvdata(dev);
+
+	memcpy(buf, drvdata->rx_data, IVC_FRAME_SIZE);
+
+	return IVC_FRAME_SIZE;
+}
+
+static ssize_t tegra_aon_ivc_echo_tx(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct tegra_aon_ivc_echo_data *drvdata = dev_get_drvdata(dev);
+	struct tegra_aon_mbox_msg msg;
+	int ret;
+
+	if (count > IVC_FRAME_SIZE) {
+		dev_err(dev, "Message is greater than the frame size %d\n",
+							IVC_FRAME_SIZE);
+		return -EINVAL;
+	}
+
+	msg.length = count;
+	msg.data = (void *)buf;
+	ret = mbox_send_message(drvdata->mbox, (void *)&msg);
+	if (ret < 0)
+		dev_err(dev, "mbox_send_message failed %d\n", ret);
+
+	return count;
+}
+
+static const DEVICE_ATTR(data_channel, S_IRUGO | S_IWUSR,
+				tegra_aon_ivc_echo_show, tegra_aon_ivc_echo_tx);
+
+static void tegra_aon_ivc_echo_rx(struct mbox_client *cl, void *data)
+{
+	struct tegra_aon_mbox_msg *msg = data;
+	struct tegra_aon_ivc_echo_data *drvdata = container_of(cl,
+					struct tegra_aon_ivc_echo_data,
+					cl);
+	memcpy(drvdata->rx_data, msg->data, IVC_FRAME_SIZE);
+}
+
+static int tegra_aon_ivc_echo_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct device *dev = &pdev->dev;
+	struct tegra_aon_ivc_echo_data *drvdata;
+
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+	dev_set_drvdata(dev, drvdata);
+	drvdata->cl.dev = dev;
+	drvdata->cl.tx_block = true;
+	drvdata->cl.tx_tout = TX_BLOCK_PERIOD;
+	drvdata->cl.knows_txdone = false;
+	drvdata->cl.rx_callback = tegra_aon_ivc_echo_rx;
+	drvdata->mbox = mbox_request_channel(&drvdata->cl, 0);
+	if (IS_ERR(drvdata->mbox)) {
+		ret = PTR_ERR(drvdata->mbox);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "mbox_request_channel failed. Error %d\n",
+									ret);
+		return ret;
+	}
+
+	ret = device_create_file(dev, &dev_attr_data_channel);
+	if (ret) {
+		dev_err(dev, "Failed to create device file. Error %d\n", ret);
+		mbox_free_channel(drvdata->mbox);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int tegra_aon_ivc_echo_remove(struct platform_device *pdev)
+{
+	struct tegra_aon_ivc_echo_data *drvdata = dev_get_drvdata(&pdev->dev);
+
+	device_remove_file(&pdev->dev, &dev_attr_data_channel);
+	mbox_free_channel(drvdata->mbox);
+
+	return 0;
+}
+
+static const struct of_device_id tegra_aon_ivc_echo_match[] = {
+	{ .compatible = "nvidia,tegra186-aon-ivc-echo", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tegra_aon_ivc_echo_match);
+
+static struct platform_driver tegra_aon_ivc_echo_driver = {
+	.probe = tegra_aon_ivc_echo_probe,
+	.remove = tegra_aon_ivc_echo_remove,
+	.driver = {
+		.name = "tegra-aon-ivc-echo",
+		.of_match_table = tegra_aon_ivc_echo_match,
+	},
+};
+module_platform_driver(tegra_aon_ivc_echo_driver);
+MODULE_LICENSE("GPL v2");