Message-Id: <1466503374-28841-7-git-send-email-narmstrong@baylibre.com>
Date:	Tue, 21 Jun 2016 12:02:51 +0200
From:	Neil Armstrong <narmstrong@...libre.com>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	sudeep.holla@....com
Cc:	Neil Armstrong <narmstrong@...libre.com>,
	linux-amlogic@...ts.infradead.org, khilman@...libre.com,
	heiko@...ech.de, wxt@...k-chips.com, frank.wang@...k-chips.com
Subject: [RFC PATCH v2 6/9] firmware: Add legacy SCPI protocol driver

Add legacy SCPI driver based on the latest SCPI driver but modified to behave
like an earlier technology preview SCPI implementation that at least the
Amlogic GXBB ARMv8 based platform uses in it's SCP firmware implementation.

The main differences between the mainline, public and recommended SCPI
implementation are :
 - virtual channels is not implemented
 - command word is passed by the MHU instead of the virtual channel ID
 - uses "sender id" in the command word for each commands groups
 - payload size shift in command word is different
 - command word is not in SRAM, so command queuing is not possible
 - command indexes are different
 - command data structures differs
 - commands are redirected to low or high priority channels by their indexes, 
   so round-robin redirection is not possible

A clear disclaimer is added to make it clear this implementation should not
be used for new products and is only here to support already released SoCs.

Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/firmware/Kconfig       |  20 ++
 drivers/firmware/Makefile      |   1 +
 drivers/firmware/legacy_scpi.c | 644 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 665 insertions(+)
 create mode 100644 drivers/firmware/legacy_scpi.c

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 95b01f4..b9c2a33 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -31,6 +31,26 @@ config ARM_SCPI_PROTOCOL
 	  This protocol library provides interface for all the client drivers
 	  making use of the features offered by the SCP.
 
+config LEGACY_SCPI_PROTOCOL
+	bool "Legacy System Control and Power Interface (SCPI) Message Protocol"
+	default y if ARCH_MESON
+	select ARM_SCPI_FW
+	help
+	  System Control and Power Interface (SCPI) Message Protocol is
+	  defined for the purpose of communication between the Application
+	  Cores(AP) and the System Control Processor(SCP). The MHU peripheral
+	  provides a mechanism for inter-processor communication between SCP
+	  and AP.
+
+	  SCP controls most of the power managament on the Application
+	  Processors. It offers control and management of: the core/cluster
+	  power states, various power domain DVFS including the core/cluster,
+	  certain system clocks configuration, thermal sensors and many
+	  others.
+
+	  This protocol library provides interface for all the client drivers
+	  making use of the features offered by the legacy SCP protocol.
+
 config EDD
 	tristate "BIOS Enhanced Disk Drive calls determine boot disk"
 	depends on X86
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index b697462..c2cac9c 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -4,6 +4,7 @@
 obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o
 obj-$(CONFIG_SCPI_FW)		+= scpi.o
 obj-$(CONFIG_ARM_SCPI_PROTOCOL)	+= arm_scpi.o
+obj-$(CONFIG_LEGACY_SCPI_PROTOCOL) += legacy_scpi.o
 obj-$(CONFIG_DMI)		+= dmi_scan.o
 obj-$(CONFIG_DMI_SYSFS)		+= dmi-sysfs.o
 obj-$(CONFIG_EDD)		+= edd.o
diff --git a/drivers/firmware/legacy_scpi.c b/drivers/firmware/legacy_scpi.c
new file mode 100644
index 0000000..4bd3ff7
--- /dev/null
+++ b/drivers/firmware/legacy_scpi.c
@@ -0,0 +1,644 @@
+/*
+ * Legacy System Control and Power Interface (SCPI) Message Protocol driver
+ *
+ * SCPI Message Protocol is used between the System Control Processor(SCP)
+ * and the Application Processors(AP). The Message Handling Unit(MHU)
+ * provides a mechanism for inter-processor communication between SCP's
+ * Cortex M3 and AP.
+ *
+ * SCP offers control and management of the core/cluster power states,
+ * various power domain DVFS including the core/cluster, certain system
+ * clocks configuration, thermal sensors and many others.
+ *
+ * Copyright (C) 2016 BayLibre, SAS.
+ * Author: Neil Armstrong <narmstrong@...libre.com>
+ *
+ * Heavily based on arm_scpi.c from :
+ * Copyright (C) 2015 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * DISCLAIMER
+ *
+ * This SCPI implementation is based on a technology preview release
+ * and new ARMv8 SoCs implementations should use the standard SCPI
+ * implementation as defined in the ARM DUI 0922G and implemented
+ * in the arm_scpi.c driver.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/printk.h>
+#include <linux/scpi_protocol.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/spinlock.h>
+
+#define CMD_ID_SHIFT		0
+#define CMD_ID_MASK		0x7f
+#define CMD_SENDER_ID_SHIFT	8
+#define CMD_SENDER_ID_MASK	0xff
+#define CMD_DATA_SIZE_SHIFT	20
+#define CMD_DATA_SIZE_MASK	0x1ff
+#define PACK_SCPI_CMD(cmd_id, sender, tx_sz)				\
+	((((cmd_id) & CMD_ID_MASK) << CMD_ID_SHIFT) |			\
+	(((sender) & CMD_SENDER_ID_MASK) << CMD_SENDER_ID_SHIFT) |	\
+	(((tx_sz) & CMD_DATA_SIZE_MASK) << CMD_DATA_SIZE_SHIFT))
+
+#define CMD_SIZE(cmd)	(((cmd) >> CMD_DATA_SIZE_SHIFT) & CMD_DATA_SIZE_MASK)
+#define CMD_UNIQ_MASK	(CMD_TOKEN_ID_MASK << CMD_TOKEN_ID_SHIFT | CMD_ID_MASK)
+#define CMD_XTRACT_UNIQ(cmd)	((cmd) & CMD_UNIQ_MASK)
+
+#define MAX_DVFS_DOMAINS	3
+#define MAX_DVFS_OPPS		16
+#define DVFS_LATENCY(hdr)	(le32_to_cpu(hdr) >> 16)
+#define DVFS_OPP_COUNT(hdr)	((le32_to_cpu(hdr) >> 8) & 0xff)
+
+#define MAX_RX_TIMEOUT          (msecs_to_jiffies(30))
+
+enum legacy_scpi_error_codes {
+	SCPI_SUCCESS = 0, /* Success */
+	SCPI_ERR_PARAM = 1, /* Invalid parameter(s) */
+	SCPI_ERR_ALIGN = 2, /* Invalid alignment */
+	SCPI_ERR_SIZE = 3, /* Invalid size */
+	SCPI_ERR_HANDLER = 4, /* Invalid handler/callback */
+	SCPI_ERR_ACCESS = 5, /* Invalid access/permission denied */
+	SCPI_ERR_RANGE = 6, /* Value out of range */
+	SCPI_ERR_TIMEOUT = 7, /* Timeout has occurred */
+	SCPI_ERR_NOMEM = 8, /* Invalid memory area or pointer */
+	SCPI_ERR_PWRSTATE = 9, /* Invalid power state */
+	SCPI_ERR_SUPPORT = 10, /* Not supported or disabled */
+	SCPI_ERR_DEVICE = 11, /* Device error */
+	SCPI_ERR_BUSY = 12, /* Device busy */
+	SCPI_ERR_MAX
+};
+
+enum legacy_scpi_client_id {
+	SCPI_CL_NONE,
+	SCPI_CL_CLOCKS,
+	SCPI_CL_DVFS,
+	SCPI_CL_POWER,
+	SCPI_CL_THERMAL,
+	SCPI_CL_REMOTE,
+	SCPI_CL_LED_TIMER,
+	SCPI_MAX,
+};
+
+enum legacy_scpi_std_cmd {
+	SCPI_CMD_INVALID		= 0x00,
+	SCPI_CMD_SCPI_READY		= 0x01,
+	SCPI_CMD_SCPI_CAPABILITIES	= 0x02,
+	SCPI_CMD_EVENT			= 0x03,
+	SCPI_CMD_SET_CSS_PWR_STATE	= 0x04,
+	SCPI_CMD_GET_CSS_PWR_STATE	= 0x05,
+	SCPI_CMD_CFG_PWR_STATE_STAT	= 0x06,
+	SCPI_CMD_GET_PWR_STATE_STAT	= 0x07,
+	SCPI_CMD_SYS_PWR_STATE		= 0x08,
+	SCPI_CMD_L2_READY		= 0x09,
+	SCPI_CMD_SET_AP_TIMER		= 0x0a,
+	SCPI_CMD_CANCEL_AP_TIME		= 0x0b,
+	SCPI_CMD_DVFS_CAPABILITIES	= 0x0c,
+	SCPI_CMD_GET_DVFS_INFO		= 0x0d,
+	SCPI_CMD_SET_DVFS		= 0x0e,
+	SCPI_CMD_GET_DVFS		= 0x0f,
+	SCPI_CMD_GET_DVFS_STAT		= 0x10,
+	SCPI_CMD_SET_RTC		= 0x11,
+	SCPI_CMD_GET_RTC		= 0x12,
+	SCPI_CMD_CLOCK_CAPABILITIES	= 0x13,
+	SCPI_CMD_SET_CLOCK_INDEX	= 0x14,
+	SCPI_CMD_SET_CLOCK_VALUE	= 0x15,
+	SCPI_CMD_GET_CLOCK_VALUE	= 0x16,
+	SCPI_CMD_PSU_CAPABILITIES	= 0x17,
+	SCPI_CMD_SET_PSU		= 0x18,
+	SCPI_CMD_GET_PSU		= 0x19,
+	SCPI_CMD_SENSOR_CAPABILITIES	= 0x1a,
+	SCPI_CMD_SENSOR_INFO		= 0x1b,
+	SCPI_CMD_SENSOR_VALUE		= 0x1c,
+	SCPI_CMD_SENSOR_CFG_PERIODIC	= 0x1d,
+	SCPI_CMD_SENSOR_CFG_BOUNDS	= 0x1e,
+	SCPI_CMD_SENSOR_ASYNC_VALUE	= 0x1f,
+	SCPI_CMD_COUNT
+};
+
+struct legacy_scpi_xfer {
+	u32 cmd;
+	u32 status;
+	const void *tx_buf;
+	void *rx_buf;
+	unsigned int tx_len;
+	unsigned int rx_len;
+	struct completion done;
+};
+
+struct legacy_scpi_chan {
+	struct mbox_client cl;
+	struct mbox_chan *chan;
+	void __iomem *tx_payload;
+	void __iomem *rx_payload;
+	spinlock_t rx_lock; /* locking for the rx pending list */
+	struct mutex xfers_lock;
+	struct legacy_scpi_xfer t;
+};
+
+struct legacy_scpi_drvinfo {
+	int num_chans;
+	struct legacy_scpi_chan *channels;
+	struct scpi_dvfs_info *dvfs[MAX_DVFS_DOMAINS];
+};
+
+/*
+ * The SCP firmware only executes in little-endian mode, so any buffers
+ * shared through SCPI should have their contents converted to little-endian
+ */
+struct legacy_scpi_shared_mem {
+	__le32 status;
+	u8 payload[0];
+} __packed;
+
+struct scp_capabilities {
+	__le32 protocol_version;
+	__le32 event_version;
+	__le32 platform_version;
+	__le32 commands[4];
+} __packed;
+
+struct clk_get_info {
+	__le16 id;
+	__le16 flags;
+	__le32 min_rate;
+	__le32 max_rate;
+	u8 name[20];
+} __packed;
+
+struct clk_get_value {
+	__le32 rate;
+} __packed;
+
+struct clk_set_value {
+	__le32 rate;
+	__le16 id;
+	__le16 reserved;
+} __packed;
+
+struct dvfs_info {
+	__le32 header;
+	struct {
+		__le32 freq;
+		__le32 m_volt;
+	} opps[MAX_DVFS_OPPS];
+} __packed;
+
+struct dvfs_get {
+	u8 index;
+} __packed;
+
+struct dvfs_set {
+	u8 domain;
+	u8 index;
+} __packed;
+
+struct sensor_capabilities {
+	__le16 sensors;
+} __packed;
+
+struct sensor_info {
+	__le16 sensor_id;
+	u8 class;
+	u8 trigger_type;
+	char name[20];
+};
+
+struct sensor_value {
+	__le32 val;
+} __packed;
+
+static struct legacy_scpi_drvinfo *legacy_scpi_info;
+
+static int legacy_scpi_linux_errmap[SCPI_ERR_MAX] = {
+	/* better than switch case as long as return value is continuous */
+	0, /* SCPI_SUCCESS */
+	-EINVAL, /* SCPI_ERR_PARAM */
+	-ENOEXEC, /* SCPI_ERR_ALIGN */
+	-EMSGSIZE, /* SCPI_ERR_SIZE */
+	-EINVAL, /* SCPI_ERR_HANDLER */
+	-EACCES, /* SCPI_ERR_ACCESS */
+	-ERANGE, /* SCPI_ERR_RANGE */
+	-ETIMEDOUT, /* SCPI_ERR_TIMEOUT */
+	-ENOMEM, /* SCPI_ERR_NOMEM */
+	-EINVAL, /* SCPI_ERR_PWRSTATE */
+	-EOPNOTSUPP, /* SCPI_ERR_SUPPORT */
+	-EIO, /* SCPI_ERR_DEVICE */
+	-EBUSY, /* SCPI_ERR_BUSY */
+};
+
+static inline int legacy_scpi_to_linux_errno(int errno)
+{
+	if (errno >= SCPI_SUCCESS && errno < SCPI_ERR_MAX)
+		return legacy_scpi_linux_errmap[errno];
+	return -EIO;
+}
+
+static void legacy_scpi_handle_remote_msg(struct mbox_client *c, void *msg)
+{
+	struct legacy_scpi_chan *ch = container_of(c, struct legacy_scpi_chan, cl);
+	struct legacy_scpi_shared_mem *mem = ch->rx_payload;
+	unsigned long flags;
+	unsigned int len;
+
+	spin_lock_irqsave(&ch->rx_lock, flags);
+
+	len = ch->t.rx_len;
+
+	ch->t.status = le32_to_cpu(mem->status);
+	if (len)
+		memcpy_fromio(ch->t.rx_buf, mem->payload, len);
+
+	complete(&ch->t.done);
+
+	spin_unlock_irqrestore(&ch->rx_lock, flags);
+}
+
+static void legacy_scpi_tx_prepare(struct mbox_client *c, void *msg)
+{
+	struct legacy_scpi_chan *ch = container_of(c, struct legacy_scpi_chan, cl);
+
+	if (ch->t.tx_buf && ch->t.tx_len)
+		memcpy_toio(ch->tx_payload, ch->t.tx_buf, ch->t.tx_len);
+}
+
+static int high_priority_cmds[] = {
+	SCPI_CMD_GET_CSS_PWR_STATE,
+	SCPI_CMD_CFG_PWR_STATE_STAT,
+	SCPI_CMD_GET_PWR_STATE_STAT,
+	SCPI_CMD_SET_DVFS,
+	SCPI_CMD_GET_DVFS,
+	SCPI_CMD_SET_RTC,
+	SCPI_CMD_GET_RTC,
+	SCPI_CMD_SET_CLOCK_INDEX,
+	SCPI_CMD_SET_CLOCK_VALUE,
+	SCPI_CMD_GET_CLOCK_VALUE,
+	SCPI_CMD_SET_PSU,
+	SCPI_CMD_GET_PSU,
+	SCPI_CMD_SENSOR_CFG_PERIODIC,
+	SCPI_CMD_SENSOR_CFG_BOUNDS,
+};
+
+static int legacy_scpi_get_chan(u8 cmd)
+{
+	int idx;
+
+	for (idx = 0; idx < ARRAY_SIZE(high_priority_cmds); idx++)
+		if (cmd == high_priority_cmds[idx])
+			return 1;
+
+	return 0;
+}
+
+static int legacy_scpi_send_message(u8 cmd, unsigned int sender,
+				void *tx_buf, unsigned int tx_len,
+				void *rx_buf, unsigned int rx_len)
+{
+	int ret;
+	u8 chan;
+	struct legacy_scpi_xfer *msg;
+	struct legacy_scpi_chan *legacy_scpi_chan;
+
+	chan = legacy_scpi_get_chan(cmd);
+	legacy_scpi_chan = legacy_scpi_info->channels + chan;
+
+	msg = &legacy_scpi_chan->t;
+
+	msg->cmd = PACK_SCPI_CMD(cmd, sender, tx_len);
+	msg->tx_buf = tx_buf;
+	msg->tx_len = tx_len;
+	msg->rx_buf = rx_buf;
+	msg->rx_len = rx_len;
+	init_completion(&msg->done);
+
+	ret = mbox_send_message(legacy_scpi_chan->chan, &msg->cmd);
+	if (ret < 0)
+		goto out;
+
+	if (!wait_for_completion_timeout(&msg->done, MAX_RX_TIMEOUT))
+		ret = -ETIMEDOUT;
+	else
+		/* first status word */
+		ret = msg->status;
+out:
+	/* SCPI error codes > 0, translate them to Linux scale*/
+	return ret > 0 ? legacy_scpi_to_linux_errno(ret) : ret;
+}
+
+static u32 legacy_scpi_get_version(void)
+{
+	/* TOFIX */
+	return 0;
+}
+
+static unsigned long legacy_scpi_clk_get_val(u16 clk_id)
+{
+	int ret;
+	struct clk_get_value clk;
+	__le16 le_clk_id = cpu_to_le16(clk_id);
+
+	ret = legacy_scpi_send_message(SCPI_CMD_GET_CLOCK_VALUE, SCPI_CL_CLOCKS,
+				&le_clk_id, sizeof(le_clk_id),
+				&clk, sizeof(clk));
+
+	return ret ? ret : le32_to_cpu(clk.rate);
+}
+
+static int legacy_scpi_clk_set_val(u16 clk_id, unsigned long rate)
+{
+	int stat;
+	struct clk_set_value clk = {
+		.id = cpu_to_le16(clk_id),
+		.rate = cpu_to_le32(rate)
+	};
+
+	return legacy_scpi_send_message(SCPI_CMD_SET_CLOCK_VALUE, SCPI_CL_CLOCKS,
+				&clk, sizeof(clk),
+				&stat, sizeof(stat));
+}
+
+static int legacy_scpi_dvfs_get_idx(u8 domain)
+{
+	int ret;
+	struct dvfs_get dvfs;
+
+	ret = legacy_scpi_send_message(SCPI_CMD_GET_DVFS, SCPI_CL_DVFS,
+				&domain, sizeof(domain),
+				&dvfs, sizeof(dvfs));
+
+	return ret ? ret : dvfs.index;
+}
+
+static int legacy_scpi_dvfs_set_idx(u8 domain, u8 index)
+{
+	int stat;
+	struct dvfs_set dvfs = {domain, index};
+
+	return legacy_scpi_send_message(SCPI_CMD_SET_DVFS, SCPI_CL_DVFS,
+				&dvfs, sizeof(dvfs),
+				&stat, sizeof(stat));
+}
+
+static struct scpi_dvfs_info *legacy_scpi_dvfs_get_info(u8 domain)
+{
+	struct scpi_dvfs_info *info;
+	struct scpi_opp *opp;
+	struct dvfs_info buf;
+	int ret, i;
+
+	if (domain >= MAX_DVFS_DOMAINS)
+		return ERR_PTR(-EINVAL);
+
+	if (legacy_scpi_info->dvfs[domain])	/* data already populated */
+		return legacy_scpi_info->dvfs[domain];
+
+	ret = legacy_scpi_send_message(SCPI_CMD_GET_DVFS_INFO, SCPI_CL_DVFS,
+				&domain, sizeof(domain),
+				&buf, sizeof(buf));
+
+	if (ret)
+		return ERR_PTR(ret);
+
+	info = kmalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return ERR_PTR(-ENOMEM);
+
+	info->count = DVFS_OPP_COUNT(buf.header);
+	info->latency = DVFS_LATENCY(buf.header) * 1000; /* uS to nS */
+
+	info->opps = kcalloc(info->count, sizeof(*opp), GFP_KERNEL);
+	if (!info->opps) {
+		kfree(info);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	for (i = 0, opp = info->opps; i < info->count; i++, opp++) {
+		opp->freq = le32_to_cpu(buf.opps[i].freq);
+		opp->m_volt = le32_to_cpu(buf.opps[i].m_volt);
+	}
+
+	legacy_scpi_info->dvfs[domain] = info;
+	return info;
+}
+
+static int legacy_scpi_sensor_get_capability(u16 *sensors)
+{
+	struct sensor_capabilities cap_buf;
+	int ret;
+
+	ret = legacy_scpi_send_message(SCPI_CMD_SENSOR_CAPABILITIES,
+				SCPI_CL_THERMAL, NULL, 0, &cap_buf,
+				sizeof(cap_buf));
+	if (!ret)
+		*sensors = le16_to_cpu(cap_buf.sensors);
+
+	return ret;
+}
+
+static int legacy_scpi_sensor_get_info(u16 sensor_id,
+				     struct scpi_sensor_info *info)
+{
+	__le16 id = cpu_to_le16(sensor_id);
+	struct sensor_info _info;
+	int ret;
+
+	ret = legacy_scpi_send_message(SCPI_CMD_SENSOR_INFO, SCPI_CL_THERMAL,
+				&id, sizeof(id),
+				&_info, sizeof(_info));
+	if (!ret) {
+		memcpy(info, &_info, sizeof(*info));
+		info->sensor_id = le16_to_cpu(_info.sensor_id);
+	}
+
+	return ret;
+}
+
+static int legacy_scpi_sensor_get_value(u16 sensor, u64 *val)
+{
+	__le16 id = cpu_to_le16(sensor);
+	struct sensor_value buf;
+	int ret;
+
+	ret = legacy_scpi_send_message(SCPI_CMD_SENSOR_VALUE, SCPI_CL_THERMAL,
+				&id, sizeof(id),
+				&buf, sizeof(buf));
+	if (!ret)
+		*val = (u64)le32_to_cpu(buf.val);
+
+	return ret;
+}
+
+static struct scpi_ops legacy_scpi_ops = {
+	.get_version = legacy_scpi_get_version,
+	.clk_get_val = legacy_scpi_clk_get_val,
+	.clk_set_val = legacy_scpi_clk_set_val,
+	.dvfs_get_idx = legacy_scpi_dvfs_get_idx,
+	.dvfs_set_idx = legacy_scpi_dvfs_set_idx,
+	.dvfs_get_info = legacy_scpi_dvfs_get_info,
+	.sensor_get_capability = legacy_scpi_sensor_get_capability,
+	.sensor_get_info = legacy_scpi_sensor_get_info,
+	.sensor_get_value = legacy_scpi_sensor_get_value,
+};
+
+static void legacy_scpi_free_channels(struct device *dev,
+				struct legacy_scpi_chan *pchan, int count)
+{
+	int i;
+
+	for (i = 0; i < count && pchan->chan; i++, pchan++)
+		mbox_free_channel(pchan->chan);
+}
+
+static int legacy_scpi_remove(struct platform_device *pdev)
+{
+	int i;
+	struct device *dev = &pdev->dev;
+	struct legacy_scpi_drvinfo *info = platform_get_drvdata(pdev);
+
+	/* stop exporting SCPI ops */
+	legacy_scpi_info = NULL;
+
+	of_platform_depopulate(dev);
+	legacy_scpi_free_channels(dev, info->channels, info->num_chans);
+	platform_set_drvdata(pdev, NULL);
+
+	for (i = 0; i < MAX_DVFS_DOMAINS && info->dvfs[i]; i++) {
+		kfree(info->dvfs[i]->opps);
+		kfree(info->dvfs[i]);
+	}
+
+	return 0;
+}
+
+static int legacy_scpi_probe(struct platform_device *pdev)
+{
+	int count, idx, ret;
+	struct resource res;
+	struct legacy_scpi_chan *legacy_scpi_chan;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+
+	legacy_scpi_info = devm_kzalloc(dev, sizeof(*legacy_scpi_info), GFP_KERNEL);
+	if (!legacy_scpi_info)
+		return -ENOMEM;
+
+	count = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
+	if (count < 0) {
+		dev_err(dev, "no mboxes property in '%s'\n", np->full_name);
+		return -ENODEV;
+	}
+
+	legacy_scpi_chan = devm_kcalloc(dev, count,
+				sizeof(*legacy_scpi_chan), GFP_KERNEL);
+	if (!legacy_scpi_chan)
+		return -ENOMEM;
+
+	for (idx = 0; idx < count; idx++) {
+		resource_size_t size;
+		struct legacy_scpi_chan *pchan = legacy_scpi_chan + idx;
+		struct mbox_client *cl = &pchan->cl;
+		struct device_node *shmem = of_parse_phandle(np, "shmem", idx);
+
+		if (of_address_to_resource(shmem, 0, &res)) {
+			dev_err(dev, "failed to get SCPI payload mem resource\n");
+			ret = -EINVAL;
+			goto err;
+		}
+
+		size = resource_size(&res);
+
+		dev_dbg(dev, "chan%d: sram start=%llx size=%lld\n",
+				idx, res.start, size);
+
+		pchan->rx_payload = devm_ioremap(dev, res.start, size);
+		if (!pchan->rx_payload) {
+			dev_err(dev, "failed to ioremap SCPI payload\n");
+			ret = -EADDRNOTAVAIL;
+			goto err;
+		}
+		pchan->tx_payload = pchan->rx_payload + (size >> 1);
+
+		dev_dbg(dev, "chan%d: payload rx=%p tx=%p\n",
+			idx, pchan->rx_payload, pchan->tx_payload);
+
+		cl->dev = dev;
+		cl->rx_callback = legacy_scpi_handle_remote_msg;
+		cl->tx_prepare = legacy_scpi_tx_prepare;
+		cl->tx_block = true;
+		cl->tx_tout = 20;
+		cl->knows_txdone = false; /* controller can't ack */
+
+		spin_lock_init(&pchan->rx_lock);
+		mutex_init(&pchan->xfers_lock);
+
+		pchan->chan = mbox_request_channel(cl, idx);
+		if (!IS_ERR(pchan->chan))
+			continue;
+		else
+			ret = PTR_ERR(pchan->chan);
+err:
+		legacy_scpi_free_channels(dev, legacy_scpi_chan, idx);
+		legacy_scpi_info = NULL;
+		return ret;
+	}
+
+	legacy_scpi_info->channels = legacy_scpi_chan;
+	legacy_scpi_info->num_chans = count;
+	platform_set_drvdata(pdev, legacy_scpi_info);
+
+	ret = devm_scpi_ops_register(dev, &legacy_scpi_ops);
+	if (ret)
+		return ret;
+
+	return of_platform_populate(dev->of_node, NULL, NULL, dev);
+}
+
+static const struct of_device_id legacy_scpi_of_match[] = {
+	{.compatible = "arm,legacy-scpi"},
+	{.compatible = "amlogic,meson-gxbb-scpi"},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, legacy_scpi_of_match);
+
+static struct platform_driver legacy_scpi_driver = {
+	.driver = {
+		.name = "legacy-scpi",
+		.of_match_table = legacy_scpi_of_match,
+	},
+	.probe = legacy_scpi_probe,
+	.remove = legacy_scpi_remove,
+};
+module_platform_driver(legacy_scpi_driver);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@....com>");
+MODULE_AUTHOR("Neil Armstrong <narmstrong@...libre.com>");
+MODULE_DESCRIPTION("ARM Legacy SCPI mailbox protocol driver");
+MODULE_LICENSE("GPL v2");
-- 
2.7.0

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