Re: [PATCH v5 2/2] mailbox: mediatek: Add mtk-vcp-mailbox driver

Chen-Yu Tsai
2025-08-22T14:18:13Z

On Fri, Aug 22, 2025 at 10:12 AM Jjian Zhou <jjian.zhou@mediatek.com> wrote:
>
> Add mtk-vcp-mailbox driver to support the communication with
> VCP remote microprocessor.
>
> Signed-off-by: Jjian Zhou <jjian.zhou@mediatek.com>

Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>

A couple minor comments below.

> ---
> drivers/mailbox/Kconfig | 9 ++
> drivers/mailbox/Makefile | 2 +
> drivers/mailbox/mtk-vcp-mailbox.c | 174 ++++++++++++++++++++++++
> include/linux/mailbox/mtk-vcp-mailbox.h | 32 +++++
> 4 files changed, 217 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 02432d4a5ccd..c28bdb855663 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -294,6 +294,15 @@ 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 Video Companion Processor 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 98a68f838486..07278871d254 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -63,6 +63,8 @@ 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..6f48215896d2
> --- /dev/null
> +++ b/drivers/mailbox/mtk-vcp-mailbox.c
> @@ -0,0 +1,174 @@
> +// 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);

Since there's only one mailbox, you can just pass the private data,
instead of passing the mbox_chan.

> +
> + /* get irq status */
> + priv->ipi_recv.irq_status = readl(priv->base + priv->cfg->clr_out);
> +
> + __ioread32_copy(priv->ipi_recv.msg, priv->base, MBOX_SLOT_MAX_SIZE / 4);
> +
> + 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 -EINVAL;
> + }
> +
> + status = readl(priv->base + priv->cfg->set_in) & BIT(ipi_info->index);
> + if (status) {
> + dev_warn(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);
> +
> + return !(readl(priv->base + priv->cfg->set_in) & BIT(ipi_info->index));
> +}
> +
> +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, 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);
> +
> + return devm_mbox_controller_register(dev, &priv->mbox);
> +}
> +
> +static const struct mtk_vcp_mbox_cfg mt8196_cfg = {
> + .set_in = 0x100,
> + .clr_out = 0x10C,

^ use lowercase for hex numbers.

> +};
> +
> +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..143fb0d06e30
> --- /dev/null
> +++ b/include/linux/mailbox/mtk-vcp-mailbox.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR MIT) */
> +/*
> + * Copyright (c) 2025 MediaTek Inc.
> + */
> +
> +#ifndef __MTK_VCP_MAILBOX_H__
> +#define __MTK_VCP_MAILBOX_H__
> +
> +#define MBOX_SLOT_MAX_SIZE 0x100 /* mbox max slot size */
> +
> +/**
> + * struct mtk_ipi_info - mailbox message info for mtk-vcp-mailbox
> + * @msg: The share buffer between IPC and mailbox driver
> + * @len: Message length
> + * @id: This is for identification purposes and not actually used
> + * by the mailbox hardware.
> + * @index: The signal number of the mailbox message.
> + * @slot_ofs: Data slot offset.
> + * @irq_status: Captures incoming signals for the RX path.
> + *
> + * It is used between IPC with mailbox driver.
> + */
> +struct mtk_ipi_info {
> + void *msg;
> + u32 len;
> + u32 id;
> + u32 index;
> + u32 slot_ofs;
> + u32 irq_status;
> +};
> +
> +#endif
> --
> 2.46.0
>