[RFC PATCH 19/31] xen/arm: Introduce ARM SMC based mailbox

[Oleksandr Tyshchenko <olekstysh@gmail.com>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

This code is completely borrowed from the patch series for Linux
which hasn't been upstreamed yet:
[PATCH v2 0/3] mailbox: arm: introduce smc triggered mailbox
https://lkml.org/lkml/2017/7/23/129

I am very excited about the idea described it a link above.
This solution lets us (who plays with ARM based SoCs with
Security Extensions enabled, but without possibility to involve
some standalone co-prossesor to control PM) have SCPI based CPUFreq
in Xen on ARM with a minimal cost.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien.grall@linaro.org>
CC: Andre Przywara <andre.przywara@linaro.org>
---
 xen/arch/arm/cpufreq/arm-smc-mailbox.c | 155 +++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 xen/arch/arm/cpufreq/arm-smc-mailbox.c

diff --git a/xen/arch/arm/cpufreq/arm-smc-mailbox.c b/xen/arch/arm/cpufreq/arm-smc-mailbox.c
new file mode 100644
index 0000000..d7b61a7
--- /dev/null
+++ b/xen/arch/arm/cpufreq/arm-smc-mailbox.c
@@ -0,0 +1,155 @@
+/*
+ *  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");
-- 
2.7.4


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