interconnect: qcom: Add interconnect RPM over SMD driver

On some Qualcomm SoCs, there is a remote processor, which controls some of
the Network-On-Chip interconnect resources. Other CPUs express their needs
by communicating with this processor. Add a driver to handle communication
with this remote processor.

Reviewed-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Georgi Djakov <[e-mail]>

drivers/interconnect/qcom/Kconfig

···
 	help
 	  This is a driver for the Qualcomm Network-on-Chip on sdm845-based
 	  platforms.
+
+config INTERCONNECT_QCOM_SMD_RPM
+	tristate

drivers/interconnect/qcom/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 
 qnoc-sdm845-objs			:= sdm845.o
+icc-smd-rpm-objs			:= smd-rpm.o
 
 obj-$(CONFIG_INTERCONNECT_QCOM_SDM845) += qnoc-sdm845.o
+obj-$(CONFIG_INTERCONNECT_QCOM_SMD_RPM) += icc-smd-rpm.o

drivers/interconnect/qcom/smd-rpm.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RPM over SMD communication wrapper for interconnects
+ *
+ * Copyright (C) 2019 Linaro Ltd
+ * Author: Georgi Djakov <[e-mail]>
+ */
+
+#include <linux/interconnect-provider.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/soc/qcom/smd-rpm.h>
+
+#include "smd-rpm.h"
+
+#define RPM_KEY_BW		0x00007762
+
+static struct qcom_smd_rpm *icc_smd_rpm;
+
+struct icc_rpm_smd_req {
+	__le32 key;
+	__le32 nbytes;
+	__le32 value;
+};
+
+bool qcom_icc_rpm_smd_available(void)
+{
+	return !!icc_smd_rpm;
+}
+EXPORT_SYMBOL_GPL(qcom_icc_rpm_smd_available);
+
+int qcom_icc_rpm_smd_send(int ctx, int rsc_type, int id, u32 val)
+{
+	struct icc_rpm_smd_req req = {
+		.key = cpu_to_le32(RPM_KEY_BW),
+		.nbytes = cpu_to_le32(sizeof(u32)),
+		.value = cpu_to_le32(val),
+	};
+
+	return qcom_rpm_smd_write(icc_smd_rpm, ctx, rsc_type, id, &req,
+				  sizeof(req));
+}
+EXPORT_SYMBOL_GPL(qcom_icc_rpm_smd_send);
+
+static int qcom_icc_rpm_smd_remove(struct platform_device *pdev)
+{
+	icc_smd_rpm = NULL;
+
+	return 0;
+}
+
+static int qcom_icc_rpm_smd_probe(struct platform_device *pdev)
+{
+	icc_smd_rpm = dev_get_drvdata(pdev->dev.parent);
+
+	if (!icc_smd_rpm) {
+		dev_err(&pdev->dev, "unable to retrieve handle to RPM\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static struct platform_driver qcom_interconnect_rpm_smd_driver = {
+	.driver = {
+		.name		= "icc_smd_rpm",
+	},
+	.probe = qcom_icc_rpm_smd_probe,
+	.remove = qcom_icc_rpm_smd_remove,
+};
+module_platform_driver(qcom_interconnect_rpm_smd_driver);
+MODULE_AUTHOR("Georgi Djakov <[e-mail]>");
+MODULE_DESCRIPTION("Qualcomm SMD RPM interconnect proxy driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:icc_smd_rpm");

drivers/interconnect/qcom/smd-rpm.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2019, Linaro Ltd.
+ * Author: Georgi Djakov <[e-mail]>
+ */
+
+#ifndef __DRIVERS_INTERCONNECT_QCOM_SMD_RPM_H
+#define __DRIVERS_INTERCONNECT_QCOM_SMD_RPM_H
+
+#include <linux/soc/qcom/smd-rpm.h>
+
+bool qcom_icc_rpm_smd_available(void);
+int qcom_icc_rpm_smd_send(int ctx, int rsc_type, int id, u32 val);
+
+#endif