[PATCH RFC v2 1/3] mailbox: mediatek: Add mtk-vcp-mailbox driver

[Jjian Zhou <jjian.zhou@mediatek.com>]

Add mtk-vcp-mailbox driver to support the communication with
VCP remote microprocessor.

Signed-off-by: Jjian Zhou <jjian.zhou@mediatek.com>
---
 drivers/mailbox/Kconfig                 |   9 ++
 drivers/mailbox/Makefile                |   2 +
 drivers/mailbox/mtk-vcp-mailbox.c       | 179 ++++++++++++++++++++++++
 include/linux/mailbox/mtk-vcp-mailbox.h |  34 +++++
 4 files changed, 224 insertions(+)
 create mode 100644 drivers/mailbox/mtk-vcp-mailbox.c
 create mode 100644 include/linux/mailbox/mtk-vcp-mailbox.h

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index ed52db272f4d..ffc4a5491462 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -275,6 +275,15 @@ config MTK_CMDQ_MBOX
 	  critical time limitation, such as updating display configuration
 	  during the vblank.
 
+config MTK_VCP_MBOX
+	tristate "MediaTek VCP Mailbox Support"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	help
+	  Say yes here to add support for the MediaTek VCP mailbox driver.
+	  The mailbox implementation provides access from the application
+	  processor to the MediaTek Video Processing Unit.
+	  If unsure say N.
+
 config ZYNQMP_IPI_MBOX
 	tristate "Xilinx ZynqMP IPI Mailbox"
 	depends on ARCH_ZYNQMP && OF
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 9a1542b55539..75a200a9d2d2 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -59,6 +59,8 @@ obj-$(CONFIG_MTK_ADSP_MBOX)	+= mtk-adsp-mailbox.o
 
 obj-$(CONFIG_MTK_CMDQ_MBOX)	+= mtk-cmdq-mailbox.o
 
+obj-$(CONFIG_MTK_VCP_MBOX)	+= mtk-vcp-mailbox.o
+
 obj-$(CONFIG_ZYNQMP_IPI_MBOX)	+= zynqmp-ipi-mailbox.o
 
 obj-$(CONFIG_SUN6I_MSGBOX)	+= sun6i-msgbox.o
diff --git a/drivers/mailbox/mtk-vcp-mailbox.c b/drivers/mailbox/mtk-vcp-mailbox.c
new file mode 100644
index 000000000000..fd7a123c71c8
--- /dev/null
+++ b/drivers/mailbox/mtk-vcp-mailbox.c
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025 MediaTek Corporation. All rights reserved.
+ * Author: Jjian Zhou <jjian.zhou.@mediatek.com>
+ */
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox/mtk-vcp-mailbox.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct mtk_vcp_mbox_priv {
+	void __iomem *base;
+	struct device *dev;
+	struct mbox_controller mbox;
+	const struct mtk_vcp_mbox_cfg *cfg;
+	struct mtk_ipi_info ipi_recv;
+};
+
+struct mtk_vcp_mbox_cfg {
+	u32 set_in;
+	u32 clr_out;
+};
+
+static inline struct mtk_vcp_mbox_priv *get_mtk_vcp_mbox_priv(struct mbox_controller *mbox)
+{
+	return container_of(mbox, struct mtk_vcp_mbox_priv, mbox);
+}
+
+static irqreturn_t mtk_vcp_mbox_irq_thread(int irq, void *data)
+{
+	struct mbox_chan *chan = data;
+	struct mtk_vcp_mbox_priv *priv = get_mtk_vcp_mbox_priv(chan->mbox);
+
+	/* get irq status */
+	priv->ipi_recv.irq_status = readl(priv->base + priv->cfg->clr_out);
+
+	__ioread32_copy(priv->ipi_recv.msg, priv->base, MAX_SLOT_NUM);
+
+	mbox_chan_received_data(chan, &priv->ipi_recv);
+
+	/* clear irq status */
+	writel(priv->ipi_recv.irq_status, priv->base + priv->cfg->clr_out);
+
+	return IRQ_HANDLED;
+}
+
+static struct mbox_chan *mtk_vcp_mbox_xlate(struct mbox_controller *mbox,
+					    const struct of_phandle_args *sp)
+{
+	if (sp->args_count)
+		return NULL;
+
+	return mbox->chans;
+}
+
+static int mtk_vcp_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+	struct mtk_vcp_mbox_priv *priv = get_mtk_vcp_mbox_priv(chan->mbox);
+	struct mtk_ipi_info *ipi_info = data;
+	u32 status;
+
+	if (!ipi_info->msg) {
+		dev_err(priv->dev, "msg buffer is NULL.\n");
+		return -ENOMEM;
+	}
+
+	status = readl(priv->base + priv->cfg->set_in) & BIT(ipi_info->index);
+	if (status) {
+		dev_err(priv->dev, "mailbox IPI %d is busy.\n", ipi_info->id);
+		return -EBUSY;
+	}
+
+	if (ipi_info->slot_ofs + ipi_info->len > MBOX_SLOT_MAX_SIZE)
+		return -EINVAL;
+	__iowrite32_copy(priv->base + ipi_info->slot_ofs, ipi_info->msg,
+			 ipi_info->len);
+
+	writel(BIT(ipi_info->index), priv->base + priv->cfg->set_in);
+
+	return 0;
+}
+
+static bool mtk_vcp_mbox_last_tx_done(struct mbox_chan *chan)
+{
+	struct mtk_ipi_info *ipi_info = chan->active_req;
+	struct mtk_vcp_mbox_priv *priv = get_mtk_vcp_mbox_priv(chan->mbox);
+	u32 op;
+
+	op = readl(priv->base + priv->cfg->set_in) & BIT(ipi_info->index);
+	return !op;
+}
+
+static const struct mbox_chan_ops mtk_vcp_mbox_chan_ops = {
+	.send_data	= mtk_vcp_mbox_send_data,
+	.last_tx_done	= mtk_vcp_mbox_last_tx_done,
+};
+
+static int mtk_vcp_mbox_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mtk_vcp_mbox_priv *priv;
+	struct mbox_controller *mbox;
+	int ret, irq;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = dev;
+	mbox = &priv->mbox;
+	mbox->dev = dev;
+	mbox->ops = &mtk_vcp_mbox_chan_ops;
+	mbox->txdone_irq = false;
+	mbox->txdone_poll = true;
+	mbox->of_xlate = mtk_vcp_mbox_xlate;
+	mbox->num_chans = 1;
+	mbox->chans = devm_kzalloc(dev, sizeof(*mbox->chans), GFP_KERNEL);
+	if (!mbox->chans)
+		return -ENOMEM;
+
+	priv->ipi_recv.msg = devm_kzalloc(dev, sizeof(u8) * MBOX_SLOT_MAX_SIZE,
+					  GFP_KERNEL);
+	if (!priv->ipi_recv.msg)
+		return -ENOMEM;
+
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->cfg = of_device_get_match_data(dev);
+	if (!priv->cfg)
+		return -EINVAL;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_threaded_irq(dev, irq, NULL,
+					mtk_vcp_mbox_irq_thread, IRQF_ONESHOT,
+					dev_name(dev), mbox->chans);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	dev_dbg(dev, "MTK VCP mailbox initialized\n");
+
+	return devm_mbox_controller_register(dev, &priv->mbox);
+}
+
+static const struct mtk_vcp_mbox_cfg mt8196_cfg = {
+	.set_in		= 0x100,
+	.clr_out	= 0x10C,
+};
+
+static const struct of_device_id mtk_vcp_mbox_of_match[] = {
+	{ .compatible = "mediatek,mt8196-vcp-mbox", .data = &mt8196_cfg },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mtk_vcp_mbox_of_match);
+
+static struct platform_driver mtk_vcp_mbox_driver = {
+	.probe		= mtk_vcp_mbox_probe,
+	.driver = {
+		.name	= "mtk_vcp_mbox",
+		.of_match_table = mtk_vcp_mbox_of_match,
+	},
+};
+module_platform_driver(mtk_vcp_mbox_driver);
+
+MODULE_AUTHOR("Jjian Zhou <jjian.zhou@mediatek.com>");
+MODULE_DESCRIPTION("MTK VCP Mailbox Controller");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mailbox/mtk-vcp-mailbox.h b/include/linux/mailbox/mtk-vcp-mailbox.h
new file mode 100644
index 000000000000..953499b7cfeb
--- /dev/null
+++ b/include/linux/mailbox/mtk-vcp-mailbox.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR MIT) */
+/*
+ * Copyright (c) 2024 MediaTek Inc.
+ */
+
+#ifndef __MTK_VCP_MAILBOX_H__
+#define __MTK_VCP_MAILBOX_H__
+
+#define MBOX_SLOT_MAX_SIZE	0x100 /* mbox max slot size */
+#define MAX_SLOT_NUM	64
+
+/**
+ * struct mtk_ipi_info - channel table that belong to mtk_ipi_device
+ * @msg: The share buffer between IPC and mailbox driver
+ * @len: Message length
+ * @id: IPI number
+ * @recv_opt: Recv option,  0:receive ,1: response
+ * @index: The pin groups number of the mailbox channel
+ * @slot_ofs: Slot offset of the mailbox channel
+ * @irq_status: Indicate which pin groups triggered the interrupt
+ *
+ * It is used between IPC with mailbox driver.
+ */
+struct mtk_ipi_info {
+	void *msg;
+	u32 len;
+	u32 id;
+	u32 recv_opt;
+	u32 index;
+	u32 slot_ofs;
+	u32 irq_status;
+};
+
+#endif
-- 
2.45.2