firmware: imx: add SCU firmware driver support

The System Controller Firmware (SCFW) is a low-level system function
which runs on a dedicated Cortex-M core to provide power, clock, and
resource management. It exists on some i.MX8 processors. e.g. i.MX8QM
(QM, QP), and i.MX8QX (QXP, DX).

This patch implements the SCU firmware IPC function and the common
message sending API sc_call_rpc.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/firmware/Kconfig

@@ -289,6 +289,7 @@ config HAVE_ARM_SMCCC
 source "drivers/firmware/broadcom/Kconfig"
 source "drivers/firmware/google/Kconfig"
 source "drivers/firmware/efi/Kconfig"
+source "drivers/firmware/imx/Kconfig"
 source "drivers/firmware/meson/Kconfig"
 source "drivers/firmware/tegra/Kconfig"
 

drivers/firmware/Makefile

@@ -31,4 +31,5 @@ obj-y				+= meson/
 obj-$(CONFIG_GOOGLE_FIRMWARE)	+= google/
 obj-$(CONFIG_EFI)		+= efi/
 obj-$(CONFIG_UEFI_CPER)		+= efi/
+obj-y				+= imx/
 obj-y				+= tegra/

drivers/firmware/imx/Kconfig

+config IMX_SCU
+	bool "IMX SCU Protocol driver"
+	depends on IMX_MBOX
+	help
+	  The System Controller Firmware (SCFW) is a low-level system function
+	  which runs on a dedicated Cortex-M core to provide power, clock, and
+	  resource management. It exists on some i.MX8 processors. e.g. i.MX8QM
+	  (QM, QP), and i.MX8QX (QXP, DX).
+
+	  This driver manages the IPC interface between host CPU and the
+	  SCU firmware running on M4.

drivers/firmware/imx/Makefile

+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_IMX_SCU)	+= imx-scu.o

drivers/firmware/imx/imx-scu.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2018 NXP
+ *  Author: Dong Aisheng <aisheng.dong@nxp.com>
+ *
+ * Implementation of the SCU IPC functions using MUs (client side).
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/firmware/imx/types.h>
+#include <linux/firmware/imx/ipc.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+#define SCU_MU_CHAN_NUM		8
+#define MAX_RX_TIMEOUT		(msecs_to_jiffies(30))
+
+struct imx_sc_chan {
+	struct imx_sc_ipc *sc_ipc;
+
+	struct mbox_client cl;
+	struct mbox_chan *ch;
+	int idx;
+};
+
+struct imx_sc_ipc {
+	/* SCU uses 4 Tx and 4 Rx channels */
+	struct imx_sc_chan chans[SCU_MU_CHAN_NUM];
+	struct device *dev;
+	struct mutex lock;
+	struct completion done;
+
+	/* temporarily store the SCU msg */
+	u32 *msg;
+	u8 rx_size;
+	u8 count;
+};
+
+/*
+ * This type is used to indicate error response for most functions.
+ */
+enum imx_sc_error_codes {
+	IMX_SC_ERR_NONE = 0,	/* Success */
+	IMX_SC_ERR_VERSION = 1,	/* Incompatible API version */
+	IMX_SC_ERR_CONFIG = 2,	/* Configuration error */
+	IMX_SC_ERR_PARM = 3,	/* Bad parameter */
+	IMX_SC_ERR_NOACCESS = 4,	/* Permission error (no access) */
+	IMX_SC_ERR_LOCKED = 5,	/* Permission error (locked) */
+	IMX_SC_ERR_UNAVAILABLE = 6,	/* Unavailable (out of resources) */
+	IMX_SC_ERR_NOTFOUND = 7,	/* Not found */
+	IMX_SC_ERR_NOPOWER = 8,	/* No power */
+	IMX_SC_ERR_IPC = 9,		/* Generic IPC error */
+	IMX_SC_ERR_BUSY = 10,	/* Resource is currently busy/active */
+	IMX_SC_ERR_FAIL = 11,	/* General I/O failure */
+	IMX_SC_ERR_LAST
+};
+
+static int imx_sc_linux_errmap[IMX_SC_ERR_LAST] = {
+	0,	 /* IMX_SC_ERR_NONE */
+	-EINVAL, /* IMX_SC_ERR_VERSION */
+	-EINVAL, /* IMX_SC_ERR_CONFIG */
+	-EINVAL, /* IMX_SC_ERR_PARM */
+	-EACCES, /* IMX_SC_ERR_NOACCESS */
+	-EACCES, /* IMX_SC_ERR_LOCKED */
+	-ERANGE, /* IMX_SC_ERR_UNAVAILABLE */
+	-EEXIST, /* IMX_SC_ERR_NOTFOUND */
+	-EPERM,	 /* IMX_SC_ERR_NOPOWER */
+	-EPIPE,	 /* IMX_SC_ERR_IPC */
+	-EBUSY,	 /* IMX_SC_ERR_BUSY */
+	-EIO,	 /* IMX_SC_ERR_FAIL */
+};
+
+static struct imx_sc_ipc *imx_sc_ipc_handle;
+
+static inline int imx_sc_to_linux_errno(int errno)
+{
+	if (errno >= IMX_SC_ERR_NONE && errno < IMX_SC_ERR_LAST)
+		return imx_sc_linux_errmap[errno];
+	return -EIO;
+}
+
+/*
+ * Get the default handle used by SCU
+ */
+int imx_scu_get_handle(struct imx_sc_ipc **ipc)
+{
+	if (!imx_sc_ipc_handle)
+		return -EPROBE_DEFER;
+
+	*ipc = imx_sc_ipc_handle;
+	return 0;
+}
+EXPORT_SYMBOL(imx_scu_get_handle);
+
+static void imx_scu_rx_callback(struct mbox_client *c, void *msg)
+{
+	struct imx_sc_chan *sc_chan = container_of(c, struct imx_sc_chan, cl);
+	struct imx_sc_ipc *sc_ipc = sc_chan->sc_ipc;
+	struct imx_sc_rpc_msg *hdr;
+	u32 *data = msg;
+
+	if (sc_chan->idx == 0) {
+		hdr = msg;
+		sc_ipc->rx_size = hdr->size;
+		dev_dbg(sc_ipc->dev, "msg rx size %u\n", sc_ipc->rx_size);
+		if (sc_ipc->rx_size > 4)
+			dev_warn(sc_ipc->dev, "RPC does not support receiving over 4 words: %u\n",
+				 sc_ipc->rx_size);
+	}
+
+	sc_ipc->msg[sc_chan->idx] = *data;
+	sc_ipc->count++;
+
+	dev_dbg(sc_ipc->dev, "mu %u msg %u 0x%x\n", sc_chan->idx,
+		sc_ipc->count, *data);
+
+	if ((sc_ipc->rx_size != 0) && (sc_ipc->count == sc_ipc->rx_size))
+		complete(&sc_ipc->done);
+}
+
+static int imx_scu_ipc_write(struct imx_sc_ipc *sc_ipc, void *msg)
+{
+	struct imx_sc_rpc_msg *hdr = msg;
+	struct imx_sc_chan *sc_chan;
+	u32 *data = msg;
+	int ret;
+	int i;
+
+	/* Check size */
+	if (hdr->size > IMX_SC_RPC_MAX_MSG)
+		return -EINVAL;
+
+	dev_dbg(sc_ipc->dev, "RPC SVC %u FUNC %u SIZE %u\n", hdr->svc,
+		hdr->func, hdr->size);
+
+	for (i = 0; i < hdr->size; i++) {
+		sc_chan = &sc_ipc->chans[i % 4];
+		ret = mbox_send_message(sc_chan->ch, &data[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * RPC command/response
+ */
+int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
+{
+	struct imx_sc_rpc_msg *hdr;
+	int ret;
+
+	if (WARN_ON(!sc_ipc || !msg))
+		return -EINVAL;
+
+	mutex_lock(&sc_ipc->lock);
+	reinit_completion(&sc_ipc->done);
+
+	sc_ipc->msg = msg;
+	sc_ipc->count = 0;
+	ret = imx_scu_ipc_write(sc_ipc, msg);
+	if (ret < 0) {
+		dev_err(sc_ipc->dev, "RPC send msg failed: %d\n", ret);
+		goto out;
+	}
+
+	if (have_resp) {
+		if (!wait_for_completion_timeout(&sc_ipc->done,
+						 MAX_RX_TIMEOUT)) {
+			dev_err(sc_ipc->dev, "RPC send msg timeout\n");
+			mutex_unlock(&sc_ipc->lock);
+			return -ETIMEDOUT;
+		}
+
+		/* response status is stored in hdr->func field */
+		hdr = msg;
+		ret = hdr->func;
+	}
+
+out:
+	mutex_unlock(&sc_ipc->lock);
+
+	dev_dbg(sc_ipc->dev, "RPC SVC done\n");
+
+	return imx_sc_to_linux_errno(ret);
+}
+EXPORT_SYMBOL(imx_scu_call_rpc);
+
+static int imx_scu_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct imx_sc_ipc *sc_ipc;
+	struct imx_sc_chan *sc_chan;
+	struct mbox_client *cl;
+	char *chan_name;
+	int ret;
+	int i;
+
+	sc_ipc = devm_kzalloc(dev, sizeof(*sc_ipc), GFP_KERNEL);
+	if (!sc_ipc)
+		return -ENOMEM;
+
+	for (i = 0; i < SCU_MU_CHAN_NUM; i++) {
+		if (i < 4)
+			chan_name = kasprintf(GFP_KERNEL, "tx%d", i);
+		else
+			chan_name = kasprintf(GFP_KERNEL, "rx%d", i - 4);
+
+		if (!chan_name)
+			return -ENOMEM;
+
+		sc_chan = &sc_ipc->chans[i];
+		cl = &sc_chan->cl;
+		cl->dev = dev;
+		cl->tx_block = false;
+		cl->knows_txdone = true;
+		cl->rx_callback = imx_scu_rx_callback;
+
+		sc_chan->sc_ipc = sc_ipc;
+		sc_chan->idx = i % 4;
+		sc_chan->ch = mbox_request_channel_byname(cl, chan_name);
+		if (IS_ERR(sc_chan->ch)) {
+			ret = PTR_ERR(sc_chan->ch);
+			if (ret != -EPROBE_DEFER)
+				dev_err(dev, "Failed to request mbox chan %s ret %d\n",
+					chan_name, ret);
+			return ret;
+		}
+
+		dev_dbg(dev, "request mbox chan %s\n", chan_name);
+		/* chan_name is not used anymore by framework */
+		kfree(chan_name);
+	}
+
+	sc_ipc->dev = dev;
+	mutex_init(&sc_ipc->lock);
+	init_completion(&sc_ipc->done);
+
+	imx_sc_ipc_handle = sc_ipc;
+
+	dev_info(dev, "NXP i.MX SCU Initialized\n");
+
+	return devm_of_platform_populate(dev);
+}
+
+static const struct of_device_id imx_scu_match[] = {
+	{ .compatible = "fsl,imx-scu", },
+	{ /* Sentinel */ }
+};
+
+static struct platform_driver imx_scu_driver = {
+	.driver = {
+		.name = "imx-scu",
+		.of_match_table = imx_scu_match,
+	},
+	.probe = imx_scu_probe,
+};
+builtin_platform_driver(imx_scu_driver);
+
+MODULE_AUTHOR("Dong Aisheng <aisheng.dong@nxp.com>");
+MODULE_DESCRIPTION("IMX SCU firmware protocol driver");
+MODULE_LICENSE("GPL v2");

include/linux/firmware/imx/ipc.h

+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2018 NXP
+ *
+ * Header file for the IPC implementation.
+ */
+
+#ifndef _SC_IPC_H
+#define _SC_IPC_H
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+#define IMX_SC_RPC_VERSION	1
+#define IMX_SC_RPC_MAX_MSG	8
+
+struct imx_sc_ipc;
+
+enum imx_sc_rpc_svc {
+	IMX_SC_RPC_SVC_UNKNOWN = 0,
+	IMX_SC_RPC_SVC_RETURN = 1,
+	IMX_SC_RPC_SVC_PM = 2,
+	IMX_SC_RPC_SVC_RM = 3,
+	IMX_SC_RPC_SVC_TIMER = 5,
+	IMX_SC_RPC_SVC_PAD = 6,
+	IMX_SC_RPC_SVC_MISC = 7,
+	IMX_SC_RPC_SVC_IRQ = 8,
+	IMX_SC_RPC_SVC_ABORT = 9
+};
+
+struct imx_sc_rpc_msg {
+	uint8_t ver;
+	uint8_t size;
+	uint8_t svc;
+	uint8_t func;
+};
+
+/*
+ * This is an function to send an RPC message over an IPC channel.
+ * It is called by client-side SCFW API function shims.
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in,out] msg         handle to a message
+ * @param[in]     have_resp   response flag
+ *
+ * If have_resp is true then this function waits for a response
+ * and returns the result in msg.
+ */
+int imx_scu_call_rpc(struct imx_sc_ipc *ipc, void *msg, bool have_resp);
+
+/*
+ * This function gets the default ipc handle used by SCU
+ *
+ * @param[out]	ipc	sc ipc handle
+ *
+ * @return Returns an error code (0 = success, failed if < 0)
+ */
+int imx_scu_get_handle(struct imx_sc_ipc **ipc);
+#endif /* _SC_IPC_H */

include/linux/firmware/imx/sci.h

+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Copyright 2017~2018 NXP
+ *
+ * Header file containing the public System Controller Interface (SCI)
+ * definitions.
+ */
+
+#ifndef _SC_SCI_H
+#define _SC_SCI_H
+
+#include <linux/firmware/imx/ipc.h>
+#include <linux/firmware/imx/types.h>
+
+#endif /* _SC_SCI_H */