[v2,4/4] mailbox: arm_mhu: Add ARM MHU doorbell driver

diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 60d224b723a1..2e06e02b2e03 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -5,7 +5,7 @@  obj-$(CONFIG_MAILBOX)		+= mailbox.o
 
 obj-$(CONFIG_MAILBOX_TEST)	+= mailbox-test.o
 
-obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o
+obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o arm_mhu_db.o
 
 obj-$(CONFIG_IMX_MBOX)	+= imx-mailbox.o
 
diff --git a/drivers/mailbox/arm_mhu_db.c b/drivers/mailbox/arm_mhu_db.c
new file mode 100644
index 000000000000..275efe4cca0c
--- /dev/null
+++ b/drivers/mailbox/arm_mhu_db.c
@@ -0,0 +1,354 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2013-2015 Fujitsu Semiconductor Ltd.
+ * Copyright (C) 2015 Linaro Ltd.
+ * Based on ARM MHU driver by Jassi Brar <jaswinder.singh@linaro.org>
+ * Copyright (C) 2020 ARM Ltd.
+ */
+
+#include <linux/amba/bus.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+#define INTR_STAT_OFS	0x0
+#define INTR_SET_OFS	0x8
+#define INTR_CLR_OFS	0x10
+
+#define MHU_LP_OFFSET	0x0
+#define MHU_HP_OFFSET	0x20
+#define MHU_SEC_OFFSET	0x200
+#define TX_REG_OFFSET	0x100
+
+#define MHU_CHANS	3	/* Secure, Non-Secure High and Low Priority */
+#define MHU_CHAN_MAX	20	/* Max channels to save on unused RAM */
+#define MHU_NUM_DOORBELLS	32
+
+struct mhu_db_link {
+	unsigned int irq;
+	void __iomem *tx_reg;
+	void __iomem *rx_reg;
+};
+
+struct arm_mhu {
+	void __iomem *base;
+	struct mhu_db_link mlink[MHU_CHANS];
+	struct mbox_controller mbox;
+	struct device *dev;
+};
+
+/**
+ * ARM MHU Mailbox allocated channel information
+ *
+ * @mhu: Pointer to parent mailbox device
+ * @pchan: Physical channel within which this doorbell resides in
+ * @doorbell: doorbell number pertaining to this channel
+ */
+struct mhu_db_channel {
+	struct arm_mhu *mhu;
+	unsigned int pchan;
+	unsigned int doorbell;
+};
+
+static inline struct mbox_chan *
+mhu_db_mbox_to_channel(struct mbox_controller *mbox, unsigned int pchan,
+		       unsigned int doorbell)
+{
+	int i;
+	struct mhu_db_channel *chan_info;
+
+	for (i = 0; i < mbox->num_chans; i++) {
+		chan_info = mbox->chans[i].con_priv;
+		if (chan_info && chan_info->pchan == pchan &&
+		    chan_info->doorbell == doorbell)
+			return &mbox->chans[i];
+	}
+
+	return NULL;
+}
+
+static void mhu_db_mbox_clear_irq(struct mbox_chan *chan)
+{
+	struct mhu_db_channel *chan_info = chan->con_priv;
+	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].rx_reg;
+
+	writel_relaxed(BIT(chan_info->doorbell), base + INTR_CLR_OFS);
+}
+
+static unsigned int mhu_db_mbox_irq_to_pchan_num(struct arm_mhu *mhu, int irq)
+{
+	unsigned int pchan;
+
+	for (pchan = 0; pchan < MHU_CHANS; pchan++)
+		if (mhu->mlink[pchan].irq == irq)
+			break;
+	return pchan;
+}
+
+static struct mbox_chan *
+mhu_db_mbox_irq_to_channel(struct arm_mhu *mhu, unsigned int pchan)
+{
+	unsigned long bits;
+	unsigned int doorbell;
+	struct mbox_chan *chan = NULL;
+	struct mbox_controller *mbox = &mhu->mbox;
+	void __iomem *base = mhu->mlink[pchan].rx_reg;
+
+	bits = readl_relaxed(base + INTR_STAT_OFS);
+	if (!bits)
+		/* No IRQs fired in specified physical channel */
+		return NULL;
+
+	/* An IRQ has fired, find the associated channel */
+	for (doorbell = 0; bits; doorbell++) {
+		if (!test_and_clear_bit(doorbell, &bits))
+			continue;
+
+		chan = mhu_db_mbox_to_channel(mbox, pchan, doorbell);
+		if (chan)
+			break;
+		dev_err(mbox->dev,
+			"Channel not registered: pchan: %d doorbell: %d\n",
+			pchan, doorbell);
+	}
+
+	return chan;
+}
+
+static irqreturn_t mhu_db_mbox_rx_handler(int irq, void *data)
+{
+	struct mbox_chan *chan;
+	struct arm_mhu *mhu = data;
+	unsigned int pchan = mhu_db_mbox_irq_to_pchan_num(mhu, irq);
+
+	while (NULL != (chan = mhu_db_mbox_irq_to_channel(mhu, pchan))) {
+		mbox_chan_received_data(chan, NULL);
+		mhu_db_mbox_clear_irq(chan);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static bool mhu_db_last_tx_done(struct mbox_chan *chan)
+{
+	struct mhu_db_channel *chan_info = chan->con_priv;
+	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].tx_reg;
+
+	if (readl_relaxed(base + INTR_STAT_OFS) & BIT(chan_info->doorbell))
+		return false;
+
+	return true;
+}
+
+static int mhu_db_send_data(struct mbox_chan *chan, void *data)
+{
+	struct mhu_db_channel *chan_info = chan->con_priv;
+	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].tx_reg;
+
+	/* Send event to co-processor */
+	writel_relaxed(BIT(chan_info->doorbell), base + INTR_SET_OFS);
+
+	return 0;
+}
+
+static int mhu_db_startup(struct mbox_chan *chan)
+{
+	mhu_db_mbox_clear_irq(chan);
+	return 0;
+}
+
+static void mhu_db_shutdown(struct mbox_chan *chan)
+{
+	struct mhu_db_channel *chan_info = chan->con_priv;
+	struct mbox_controller *mbox = &chan_info->mhu->mbox;
+	int i;
+
+	for (i = 0; i < mbox->num_chans; i++)
+		if (chan == &mbox->chans[i])
+			break;
+
+	if (mbox->num_chans == i) {
+		dev_warn(mbox->dev, "Request to free non-existent channel\n");
+		return;
+	}
+
+	/* Reset channel */
+	mhu_db_mbox_clear_irq(chan);
+	kfree(chan->con_priv);
+	chan->con_priv = NULL;
+}
+
+static struct mbox_chan *mhu_db_mbox_xlate(struct mbox_controller *mbox,
+					   const struct of_phandle_args *spec)
+{
+	struct arm_mhu *mhu = dev_get_drvdata(mbox->dev);
+	struct mhu_db_channel *chan_info;
+	struct mbox_chan *chan;
+	unsigned int pchan = spec->args[0];
+	unsigned int doorbell = spec->args[1];
+	int i;
+
+	/* Bounds checking */
+	if (pchan >= MHU_CHANS || doorbell >= MHU_NUM_DOORBELLS) {
+		dev_err(mbox->dev,
+			"Invalid channel requested pchan: %d doorbell: %d\n",
+			pchan, doorbell);
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* Is requested channel free? */
+	chan = mhu_db_mbox_to_channel(mbox, pchan, doorbell);
+	if (chan) {
+		dev_err(mbox->dev, "Channel in use: pchan: %d doorbell: %d\n",
+			pchan, doorbell);
+		return ERR_PTR(-EBUSY);
+	}
+
+	/* Find the first free slot */
+	for (i = 0; i < mbox->num_chans; i++)
+		if (!mbox->chans[i].con_priv)
+			break;
+
+	if (mbox->num_chans == i) {
+		dev_err(mbox->dev, "No free channels left\n");
+		return ERR_PTR(-EBUSY);
+	}
+
+	chan = &mbox->chans[i];
+
+	chan_info = devm_kzalloc(mbox->dev, sizeof(*chan_info), GFP_KERNEL);
+	if (!chan_info)
+		return ERR_PTR(-ENOMEM);
+
+	chan_info->mhu = mhu;
+	chan_info->pchan = pchan;
+	chan_info->doorbell = doorbell;
+
+	chan->con_priv = chan_info;
+
+	dev_dbg(mbox->dev, "mbox: created channel phys: %d doorbell: %d\n",
+		pchan, doorbell);
+
+	return chan;
+}
+
+static const struct mbox_chan_ops mhu_db_ops = {
+	.send_data = mhu_db_send_data,
+	.startup = mhu_db_startup,
+	.shutdown = mhu_db_shutdown,
+	.last_tx_done = mhu_db_last_tx_done,
+};
+
+static int mhu_db_probe(struct amba_device *adev, const struct amba_id *id)
+{
+	u32 cell_count;
+	int i, err, max_chans;
+	struct arm_mhu *mhu;
+	struct mbox_chan *chans;
+	struct device *dev = &adev->dev;
+	struct device_node *np = dev->of_node;
+	int mhu_reg[MHU_CHANS] = {
+		MHU_LP_OFFSET, MHU_HP_OFFSET, MHU_SEC_OFFSET,
+	};
+
+	if (!of_device_is_compatible(np, "arm,mhu-doorbell"))
+		return -ENODEV;
+
+	err = of_property_read_u32(np, "#mbox-cells", &cell_count);
+	if (err) {
+		dev_err(dev, "failed to read #mbox-cells in '%pOF'\n", np);
+		return err;
+	}
+
+	if (cell_count == 2) {
+		max_chans = MHU_CHAN_MAX;
+	} else {
+		dev_err(dev, "incorrect value of #mbox-cells in '%pOF'\n", np);
+		return -EINVAL;
+	}
+
+	mhu = devm_kzalloc(dev, sizeof(*mhu), GFP_KERNEL);
+	if (!mhu)
+		return -ENOMEM;
+
+	mhu->base = devm_ioremap_resource(dev, &adev->res);
+	if (IS_ERR(mhu->base)) {
+		dev_err(dev, "ioremap failed\n");
+		return PTR_ERR(mhu->base);
+	}
+
+	chans = devm_kcalloc(dev, max_chans, sizeof(*chans), GFP_KERNEL);
+	if (!chans)
+		return -ENOMEM;
+
+	mhu->dev = dev;
+	mhu->mbox.dev = dev;
+	mhu->mbox.chans = chans;
+	mhu->mbox.num_chans = max_chans;
+	mhu->mbox.txdone_irq = false;
+	mhu->mbox.txdone_poll = true;
+	mhu->mbox.txpoll_period = 1;
+
+	mhu->mbox.of_xlate = mhu_db_mbox_xlate;
+	amba_set_drvdata(adev, mhu);
+
+	mhu->mbox.ops = &mhu_db_ops;
+
+	err = devm_mbox_controller_register(dev, &mhu->mbox);
+	if (err) {
+		dev_err(dev, "Failed to register mailboxes %d\n", err);
+		return err;
+	}
+
+	for (i = 0; i < MHU_CHANS; i++) {
+		int irq = mhu->mlink[i].irq = adev->irq[i];
+
+		if (irq <= 0) {
+			dev_dbg(dev, "No IRQ found for Channel %d\n", i);
+			continue;
+		}
+
+		mhu->mlink[i].rx_reg = mhu->base + mhu_reg[i];
+		mhu->mlink[i].tx_reg = mhu->mlink[i].rx_reg + TX_REG_OFFSET;
+
+		err = devm_request_threaded_irq(dev, irq, NULL,
+						mhu_db_mbox_rx_handler,
+						IRQF_ONESHOT, "mhu_db_link", mhu);
+		if (err) {
+			dev_err(dev, "Can't claim IRQ %d\n", irq);
+			mbox_controller_unregister(&mhu->mbox);
+			return err;
+		}
+	}
+
+	dev_info(dev, "ARM MHU Doorbell mailbox registered\n");
+	return 0;
+}
+
+static struct amba_id mhu_ids[] = {
+	{
+		.id	= 0x1bb098,
+		.mask	= 0xffffff,
+	},
+	{ 0, 0 },
+};
+MODULE_DEVICE_TABLE(amba, mhu_ids);
+
+static struct amba_driver arm_mhu_db_driver = {
+	.drv = {
+		.name	= "mhu-doorbell",
+	},
+	.id_table	= mhu_ids,
+	.probe		= mhu_db_probe,
+};
+module_amba_driver(arm_mhu_db_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ARM MHU Doorbell Driver");
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");