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+/*
+ * Copyright (C) 2016,2017 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This device provides a mechanism for emulating a mailbox by using
+ * smc calls, allowing a "mailbox" consumer to sit in firmware running
+ * on the same core.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/arm-smccc.h>
+
+#define ARM_SMC_MBOX_USE_HVC BIT(0)
+
+struct arm_smc_chan_data {
+ u32 function_id;
+ u32 flags;
+};
+
+static int arm_smc_send_data(struct mbox_chan *link, void *data)
+{
+ struct arm_smc_chan_data *chan_data = link->con_priv;
+ u32 function_id = chan_data->function_id;
+ struct arm_smccc_res res;
+ u32 msg = *(u32 *)data;
+
+ if (chan_data->flags & ARM_SMC_MBOX_USE_HVC)
+ arm_smccc_hvc(function_id, msg, 0, 0, 0, 0, 0, 0, &res);
+ else
+ arm_smccc_smc(function_id, msg, 0, 0, 0, 0, 0, 0, &res);
+
+ mbox_chan_received_data(link, (void *)res.a0);
+
+ return 0;
+}
+
+/* This mailbox is synchronous, so we are always done. */
+static bool arm_smc_last_tx_done(struct mbox_chan *link)
+{
+ return true;
+}
+
+static const struct mbox_chan_ops arm_smc_mbox_chan_ops = {
+ .send_data = arm_smc_send_data,
+ .last_tx_done = arm_smc_last_tx_done
+};
+
+static int arm_smc_mbox_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct mbox_controller *mbox;
+ struct arm_smc_chan_data *chan_data;
+ const char *method;
+ bool use_hvc = false;
+ int ret, i;
+
+ ret = of_property_count_elems_of_size(dev->of_node, "arm,func-ids",
+ sizeof(u32));
+ if (ret < 0)
+ return ret;
+
+ if (!of_property_read_string(dev->of_node, "method", &method)) {
+ if (!strcmp("hvc", method)) {
+ use_hvc = true;
+ } else if (!strcmp("smc", method)) {
+ use_hvc = false;
+ } else {
+ dev_warn(dev, "invalid \"method\" property: %s\n",
+ method);
+
+ return -EINVAL;
+ }
+ }
+
+ mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+ if (!mbox)
+ return -ENOMEM;
+
+ mbox->num_chans = ret;
+ mbox->chans = devm_kcalloc(dev, mbox->num_chans, sizeof(*mbox->chans),
+ GFP_KERNEL);
+ if (!mbox->chans)
+ return -ENOMEM;
+
+ chan_data = devm_kcalloc(dev, mbox->num_chans, sizeof(*chan_data),
+ GFP_KERNEL);
+ if (!chan_data)
+ return -ENOMEM;
+
+ for (i = 0; i < mbox->num_chans; i++) {
+ u32 function_id;
+
+ ret = of_property_read_u32_index(dev->of_node,
+ "arm,func-ids", i,
+ &function_id);
+ if (ret)
+ return ret;
+
+ chan_data[i].function_id = function_id;
+ if (use_hvc)
+ chan_data[i].flags |= ARM_SMC_MBOX_USE_HVC;
+ mbox->chans[i].con_priv = &chan_data[i];
+ }
+
+ mbox->txdone_poll = true;
+ mbox->txdone_irq = false;
+ mbox->txpoll_period = 1;
+ mbox->ops = &arm_smc_mbox_chan_ops;
+ mbox->dev = dev;
+
+ ret = mbox_controller_register(mbox);
+ if (ret)
+ return ret;
+
+ platform_set_drvdata(pdev, mbox);
+ dev_info(dev, "ARM SMC mailbox enabled with %d chan%s.\n",
+ mbox->num_chans, mbox->num_chans == 1 ? "" : "s");
+
+ return ret;
+}
+
+static int arm_smc_mbox_remove(struct platform_device *pdev)
+{
+ struct mbox_controller *mbox = platform_get_drvdata(pdev);
+
+ mbox_controller_unregister(mbox);
+ return 0;
+}
+
+static const struct of_device_id arm_smc_mbox_of_match[] = {
+ { .compatible = "arm,smc-mbox", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, arm_smc_mbox_of_match);
+
+static struct platform_driver arm_smc_mbox_driver = {
+ .driver = {
+ .name = "arm-smc-mbox",
+ .of_match_table = arm_smc_mbox_of_match,
+ },
+ .probe = arm_smc_mbox_probe,
+ .remove = arm_smc_mbox_remove,
+};
+module_platform_driver(arm_smc_mbox_driver);
+
+MODULE_AUTHOR("Andre Przywara <andre.przywara@arm.com>");
+MODULE_DESCRIPTION("Generic ARM smc mailbox driver");
+MODULE_LICENSE("GPL v2");