Date:   Wed, 16 Nov 2016 18:41:33 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jassi Brar <jassisinghbrar@...il.com>
Cc:     Joseph Lo <josephl@...dia.com>, Jon Hunter <jonathanh@...dia.com>,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5] mailbox: Add Tegra HSP driver

From: Thierry Reding <treding@...dia.com>

This driver exposes a mailbox interface for interprocessor communication
using the Hardware Synchronization Primitives (HSP) module's doorbell
mechanism. There are multiple HSP instances and they provide additional
features such as shared mailboxes, shared and arbitrated semaphores.

A driver for a remote processor can use the mailbox client provided by
the HSP driver and build an IPC protocol on top of this synchronization
mechanism.

Based on work by Joseph Lo <josephl@...dia.com>.

Signed-off-by: Thierry Reding <treding@...dia.com>
---
Changes in v5:
- remove unused ->last_tx_done() callback
- get rid of extra layer of indirection
- drop useless to_tegra_hsp_channel()

Changes in v4:
- check for doorbell ring before enabling new master
- add missing space in Kconfig description
- remove unnecessary barriers
- simplify doorbell lookup
- remove debug leftovers

Changes in v3:
- use a more object oriented design
- fix some locking issues

 drivers/mailbox/Kconfig     |   9 +
 drivers/mailbox/Makefile    |   2 +
 drivers/mailbox/tegra-hsp.c | 479 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 490 insertions(+)
 create mode 100644 drivers/mailbox/tegra-hsp.c

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 11eebfe8a4cb..ceff415f201c 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -124,6 +124,15 @@ config MAILBOX_TEST
 	  Test client to help with testing new Controller driver
 	  implementations.
 
+config TEGRA_HSP_MBOX
+	bool "Tegra HSP (Hardware Synchronization Primitives) Driver"
+	depends on ARCH_TEGRA_186_SOC
+	help
+	  The Tegra HSP driver is used for the interprocessor communication
+	  between different remote processors and host processors on Tegra186
+	  and later SoCs. Say Y here if you want to have this support.
+	  If unsure say N.
+
 config XGENE_SLIMPRO_MBOX
 	tristate "APM SoC X-Gene SLIMpro Mailbox Controller"
 	depends on ARCH_XGENE
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index ace6fed8fea9..7dde4f609ae8 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -29,3 +29,5 @@ obj-$(CONFIG_XGENE_SLIMPRO_MBOX) += mailbox-xgene-slimpro.o
 obj-$(CONFIG_HI6220_MBOX)	+= hi6220-mailbox.o
 
 obj-$(CONFIG_BCM_PDC_MBOX)	+= bcm-pdc-mailbox.o
+
+obj-$(CONFIG_TEGRA_HSP_MBOX)	+= tegra-hsp.o
diff --git a/drivers/mailbox/tegra-hsp.c b/drivers/mailbox/tegra-hsp.c
new file mode 100644
index 000000000000..3724f2fcd371
--- /dev/null
+++ b/drivers/mailbox/tegra-hsp.c
@@ -0,0 +1,479 @@
+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * 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.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mailbox_controller.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <dt-bindings/mailbox/tegra186-hsp.h>
+
+#define HSP_INT_DIMENSIONING	0x380
+#define HSP_nSM_SHIFT		0
+#define HSP_nSS_SHIFT		4
+#define HSP_nAS_SHIFT		8
+#define HSP_nDB_SHIFT		12
+#define HSP_nSI_SHIFT		16
+#define HSP_nINT_MASK		0xf
+
+#define HSP_DB_TRIGGER	0x0
+#define HSP_DB_ENABLE	0x4
+#define HSP_DB_RAW	0x8
+#define HSP_DB_PENDING	0xc
+
+#define HSP_DB_CCPLEX		1
+#define HSP_DB_BPMP		3
+#define HSP_DB_MAX		7
+
+struct tegra_hsp_channel;
+struct tegra_hsp;
+
+struct tegra_hsp_channel {
+	struct tegra_hsp *hsp;
+	struct mbox_chan *chan;
+	void __iomem *regs;
+};
+
+struct tegra_hsp_doorbell {
+	struct tegra_hsp_channel channel;
+	struct list_head list;
+	const char *name;
+	unsigned int master;
+	unsigned int index;
+};
+
+struct tegra_hsp_db_map {
+	const char *name;
+	unsigned int master;
+	unsigned int index;
+};
+
+struct tegra_hsp_soc {
+	const struct tegra_hsp_db_map *map;
+};
+
+struct tegra_hsp {
+	const struct tegra_hsp_soc *soc;
+	struct mbox_controller mbox;
+	void __iomem *regs;
+	unsigned int irq;
+	unsigned int num_sm;
+	unsigned int num_as;
+	unsigned int num_ss;
+	unsigned int num_db;
+	unsigned int num_si;
+	spinlock_t lock;
+
+	struct list_head doorbells;
+};
+
+static inline struct tegra_hsp *
+to_tegra_hsp(struct mbox_controller *mbox)
+{
+	return container_of(mbox, struct tegra_hsp, mbox);
+}
+
+static inline u32 tegra_hsp_readl(struct tegra_hsp *hsp, unsigned int offset)
+{
+	return readl(hsp->regs + offset);
+}
+
+static inline void tegra_hsp_writel(struct tegra_hsp *hsp, u32 value,
+				    unsigned int offset)
+{
+	writel(value, hsp->regs + offset);
+}
+
+static inline u32 tegra_hsp_channel_readl(struct tegra_hsp_channel *channel,
+					  unsigned int offset)
+{
+	return readl(channel->regs + offset);
+}
+
+static inline void tegra_hsp_channel_writel(struct tegra_hsp_channel *channel,
+					    u32 value, unsigned int offset)
+{
+	writel(value, channel->regs + offset);
+}
+
+static bool tegra_hsp_doorbell_can_ring(struct tegra_hsp_doorbell *db)
+{
+	u32 value;
+
+	value = tegra_hsp_channel_readl(&db->channel, HSP_DB_ENABLE);
+
+	return (value & BIT(TEGRA_HSP_DB_MASTER_CCPLEX)) != 0;
+}
+
+static struct tegra_hsp_doorbell *
+__tegra_hsp_doorbell_get(struct tegra_hsp *hsp, unsigned int master)
+{
+	struct tegra_hsp_doorbell *entry;
+
+	list_for_each_entry(entry, &hsp->doorbells, list)
+		if (entry->master == master)
+			return entry;
+
+	return NULL;
+}
+
+static struct tegra_hsp_doorbell *
+tegra_hsp_doorbell_get(struct tegra_hsp *hsp, unsigned int master)
+{
+	struct tegra_hsp_doorbell *db;
+	unsigned long flags;
+
+	spin_lock_irqsave(&hsp->lock, flags);
+	db = __tegra_hsp_doorbell_get(hsp, master);
+	spin_unlock_irqrestore(&hsp->lock, flags);
+
+	return db;
+}
+
+static irqreturn_t tegra_hsp_doorbell_irq(int irq, void *data)
+{
+	struct tegra_hsp *hsp = data;
+	struct tegra_hsp_doorbell *db;
+	unsigned long master, value;
+
+	db = tegra_hsp_doorbell_get(hsp, TEGRA_HSP_DB_MASTER_CCPLEX);
+	if (!db)
+		return IRQ_NONE;
+
+	value = tegra_hsp_channel_readl(&db->channel, HSP_DB_PENDING);
+	tegra_hsp_channel_writel(&db->channel, value, HSP_DB_PENDING);
+
+	spin_lock(&hsp->lock);
+
+	for_each_set_bit(master, &value, hsp->mbox.num_chans) {
+		struct tegra_hsp_doorbell *db;
+
+		db = __tegra_hsp_doorbell_get(hsp, master);
+		/*
+		 * Depending on the bootloader chain, the CCPLEX doorbell will
+		 * have some doorbells enabled, which means that requesting an
+		 * interrupt will immediately fire.
+		 *
+		 * In that case, db->channel.chan will still be NULL here and
+		 * cause a crash if not properly guarded.
+		 *
+		 * It remains to be seen if ignoring the doorbell in that case
+		 * is the correct solution.
+		 */
+		if (db && db->channel.chan)
+			mbox_chan_received_data(db->channel.chan, NULL);
+	}
+
+	spin_unlock(&hsp->lock);
+
+	return IRQ_HANDLED;
+}
+
+static struct tegra_hsp_channel *
+tegra_hsp_doorbell_create(struct tegra_hsp *hsp, const char *name,
+			  unsigned int master, unsigned int index)
+{
+	struct tegra_hsp_doorbell *db;
+	unsigned int offset;
+	unsigned long flags;
+
+	db = kzalloc(sizeof(*db), GFP_KERNEL);
+	if (!db)
+		return ERR_PTR(-ENOMEM);
+
+	offset = (1 + (hsp->num_sm / 2) + hsp->num_ss + hsp->num_as) << 16;
+	offset += index * 0x100;
+
+	db->channel.regs = hsp->regs + offset;
+	db->channel.hsp = hsp;
+
+	db->name = kstrdup_const(name, GFP_KERNEL);
+	db->master = master;
+	db->index = index;
+
+	spin_lock_irqsave(&hsp->lock, flags);
+	list_add_tail(&db->list, &hsp->doorbells);
+	spin_unlock_irqrestore(&hsp->lock, flags);
+
+	return &db->channel;
+}
+
+static void __tegra_hsp_doorbell_destroy(struct tegra_hsp_doorbell *db)
+{
+	list_del(&db->list);
+	kfree_const(db->name);
+	kfree(db);
+}
+
+static int tegra_hsp_doorbell_send_data(struct mbox_chan *chan, void *data)
+{
+	struct tegra_hsp_doorbell *db = chan->con_priv;
+
+	tegra_hsp_channel_writel(&db->channel, 1, HSP_DB_TRIGGER);
+
+	return 0;
+}
+
+static int tegra_hsp_doorbell_startup(struct mbox_chan *chan)
+{
+	struct tegra_hsp_doorbell *db = chan->con_priv;
+	struct tegra_hsp *hsp = db->channel.hsp;
+	struct tegra_hsp_doorbell *ccplex;
+	unsigned long flags;
+	u32 value;
+
+	if (db->master >= hsp->mbox.num_chans) {
+		dev_err(hsp->mbox.dev,
+			"invalid master ID %u for HSP channel\n",
+			db->master);
+		return -EINVAL;
+	}
+
+	ccplex = tegra_hsp_doorbell_get(hsp, TEGRA_HSP_DB_MASTER_CCPLEX);
+	if (!ccplex)
+		return -ENODEV;
+
+	if (!tegra_hsp_doorbell_can_ring(db))
+		return -ENODEV;
+
+	spin_lock_irqsave(&hsp->lock, flags);
+
+	value = tegra_hsp_channel_readl(&ccplex->channel, HSP_DB_ENABLE);
+	value |= BIT(db->master);
+	tegra_hsp_channel_writel(&ccplex->channel, value, HSP_DB_ENABLE);
+
+	spin_unlock_irqrestore(&hsp->lock, flags);
+
+	return 0;
+}
+
+static void tegra_hsp_doorbell_shutdown(struct mbox_chan *chan)
+{
+	struct tegra_hsp_doorbell *db = chan->con_priv;
+	struct tegra_hsp *hsp = db->channel.hsp;
+	struct tegra_hsp_doorbell *ccplex;
+	unsigned long flags;
+	u32 value;
+
+	ccplex = tegra_hsp_doorbell_get(hsp, TEGRA_HSP_DB_MASTER_CCPLEX);
+	if (!ccplex)
+		return;
+
+	spin_lock_irqsave(&hsp->lock, flags);
+
+	value = tegra_hsp_channel_readl(&ccplex->channel, HSP_DB_ENABLE);
+	value &= ~BIT(db->master);
+	tegra_hsp_channel_writel(&ccplex->channel, value, HSP_DB_ENABLE);
+
+	spin_unlock_irqrestore(&hsp->lock, flags);
+}
+
+static const struct mbox_chan_ops tegra_hsp_doorbell_ops = {
+	.send_data = tegra_hsp_doorbell_send_data,
+	.startup = tegra_hsp_doorbell_startup,
+	.shutdown = tegra_hsp_doorbell_shutdown,
+};
+
+static struct mbox_chan *of_tegra_hsp_xlate(struct mbox_controller *mbox,
+					    const struct of_phandle_args *args)
+{
+	struct tegra_hsp_channel *channel = ERR_PTR(-ENODEV);
+	struct tegra_hsp *hsp = to_tegra_hsp(mbox);
+	unsigned int type = args->args[0];
+	unsigned int master = args->args[1];
+	struct tegra_hsp_doorbell *db;
+	struct mbox_chan *chan;
+	unsigned long flags;
+	unsigned int i;
+
+	switch (type) {
+	case TEGRA_HSP_MBOX_TYPE_DB:
+		db = tegra_hsp_doorbell_get(hsp, master);
+		if (db)
+			channel = &db->channel;
+
+		break;
+
+	default:
+		break;
+	}
+
+	if (IS_ERR(channel))
+		return ERR_CAST(channel);
+
+	spin_lock_irqsave(&hsp->lock, flags);
+
+	for (i = 0; i < hsp->mbox.num_chans; i++) {
+		chan = &hsp->mbox.chans[i];
+		if (!chan->con_priv) {
+			chan->con_priv = channel;
+			channel->chan = chan;
+			break;
+		}
+
+		chan = NULL;
+	}
+
+	spin_unlock_irqrestore(&hsp->lock, flags);
+
+	return chan ?: ERR_PTR(-EBUSY);
+}
+
+static void tegra_hsp_remove_doorbells(struct tegra_hsp *hsp)
+{
+	struct tegra_hsp_doorbell *db;
+	unsigned long flags;
+
+	spin_lock_irqsave(&hsp->lock, flags);
+
+	list_for_each_entry(db, &hsp->doorbells, list)
+		__tegra_hsp_doorbell_destroy(db);
+
+	spin_unlock_irqrestore(&hsp->lock, flags);
+}
+
+static int tegra_hsp_add_doorbells(struct tegra_hsp *hsp)
+{
+	const struct tegra_hsp_db_map *map = hsp->soc->map;
+	struct tegra_hsp_channel *channel;
+
+	while (map->name) {
+		channel = tegra_hsp_doorbell_create(hsp, map->name,
+						    map->master, map->index);
+		if (IS_ERR(channel)) {
+			tegra_hsp_remove_doorbells(hsp);
+			return PTR_ERR(channel);
+		}
+
+		map++;
+	}
+
+	return 0;
+}
+
+static int tegra_hsp_probe(struct platform_device *pdev)
+{
+	struct tegra_hsp *hsp;
+	struct resource *res;
+	u32 value;
+	int err;
+
+	hsp = devm_kzalloc(&pdev->dev, sizeof(*hsp), GFP_KERNEL);
+	if (!hsp)
+		return -ENOMEM;
+
+	hsp->soc = of_device_get_match_data(&pdev->dev);
+	INIT_LIST_HEAD(&hsp->doorbells);
+	spin_lock_init(&hsp->lock);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	hsp->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(hsp->regs))
+		return PTR_ERR(hsp->regs);
+
+	value = tegra_hsp_readl(hsp, HSP_INT_DIMENSIONING);
+	hsp->num_sm = (value >> HSP_nSM_SHIFT) & HSP_nINT_MASK;
+	hsp->num_ss = (value >> HSP_nSS_SHIFT) & HSP_nINT_MASK;
+	hsp->num_as = (value >> HSP_nAS_SHIFT) & HSP_nINT_MASK;
+	hsp->num_db = (value >> HSP_nDB_SHIFT) & HSP_nINT_MASK;
+	hsp->num_si = (value >> HSP_nSI_SHIFT) & HSP_nINT_MASK;
+
+	err = platform_get_irq_byname(pdev, "doorbell");
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to get doorbell IRQ: %d\n", err);
+		return err;
+	}
+
+	hsp->irq = err;
+
+	hsp->mbox.of_xlate = of_tegra_hsp_xlate;
+	hsp->mbox.num_chans = 32;
+	hsp->mbox.dev = &pdev->dev;
+	hsp->mbox.txdone_irq = false;
+	hsp->mbox.txdone_poll = false;
+	hsp->mbox.ops = &tegra_hsp_doorbell_ops;
+
+	hsp->mbox.chans = devm_kcalloc(&pdev->dev, hsp->mbox.num_chans,
+					sizeof(*hsp->mbox.chans),
+					GFP_KERNEL);
+	if (!hsp->mbox.chans)
+		return -ENOMEM;
+
+	err = tegra_hsp_add_doorbells(hsp);
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to add doorbells: %d\n", err);
+		return err;
+	}
+
+	platform_set_drvdata(pdev, hsp);
+
+	err = mbox_controller_register(&hsp->mbox);
+	if (err) {
+		dev_err(&pdev->dev, "failed to register mailbox: %d\n", err);
+		tegra_hsp_remove_doorbells(hsp);
+		return err;
+	}
+
+	err = devm_request_irq(&pdev->dev, hsp->irq, tegra_hsp_doorbell_irq,
+			       IRQF_NO_SUSPEND, dev_name(&pdev->dev), hsp);
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to request IRQ#%u: %d\n",
+			hsp->irq, err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int tegra_hsp_remove(struct platform_device *pdev)
+{
+	struct tegra_hsp *hsp = platform_get_drvdata(pdev);
+
+	mbox_controller_unregister(&hsp->mbox);
+	tegra_hsp_remove_doorbells(hsp);
+
+	return 0;
+}
+
+static const struct tegra_hsp_db_map tegra186_hsp_db_map[] = {
+	{ "ccplex", TEGRA_HSP_DB_MASTER_CCPLEX, HSP_DB_CCPLEX, },
+	{ "bpmp",   TEGRA_HSP_DB_MASTER_BPMP,   HSP_DB_BPMP,   },
+	{ /* sentinel */ }
+};
+
+static const struct tegra_hsp_soc tegra186_hsp_soc = {
+	.map = tegra186_hsp_db_map,
+};
+
+static const struct of_device_id tegra_hsp_match[] = {
+	{ .compatible = "nvidia,tegra186-hsp", .data = &tegra186_hsp_soc },
+	{ }
+};
+
+static struct platform_driver tegra_hsp_driver = {
+	.driver = {
+		.name = "tegra-hsp",
+		.of_match_table = tegra_hsp_match,
+	},
+	.probe = tegra_hsp_probe,
+	.remove = tegra_hsp_remove,
+};
+
+static int __init tegra_hsp_init(void)
+{
+	return platform_driver_register(&tegra_hsp_driver);
+}
+core_initcall(tegra_hsp_init);
-- 
2.10.2

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