Re: [PATCH 3/3] mailbox: mediatek: Add mtk-apu-mailbox driver

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 24/10/24 11:25, Karl.Li ha scritto:
> From: Karl Li <karl.li@mediatek.com>
> 
> Add mtk-apu-mailbox driver to support the communication with
> APU remote microprocessor.
> 
> Also, the mailbox hardware contains extra spare (scratch) registers
> that other hardware blocks use to communicate through.
> Expose these with custom mtk_apu_mbox_(read|write)() functions.
> 
> Signed-off-by: Karl Li <karl.li@mediatek.com>
> ---
>   drivers/mailbox/Kconfig                 |   9 +
>   drivers/mailbox/Makefile                |   2 +
>   drivers/mailbox/mtk-apu-mailbox.c       | 222 ++++++++++++++++++++++++
>   include/linux/mailbox/mtk-apu-mailbox.h |  20 +++
>   4 files changed, 253 insertions(+)
>   create mode 100644 drivers/mailbox/mtk-apu-mailbox.c
>   create mode 100644 include/linux/mailbox/mtk-apu-mailbox.h
> 
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index 6fb995778636..2338e08a110a 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -240,6 +240,15 @@ config MTK_ADSP_MBOX
>             between processors with ADSP. It will place the message to share
>   	  buffer and will access the ipc control.
>   
> +config MTK_APU_MBOX
> +	tristate "MediaTek APU Mailbox Support"
> +	depends on ARCH_MEDIATEK || COMPILE_TEST
> +	help
> +	  Say yes here to add support for the MediaTek APU Mailbox
> +	  driver. The mailbox implementation provides access from the
> +	  application processor to the MediaTek AI Processing Unit.
> +	  If unsure say N.
> +
>   config MTK_CMDQ_MBOX
>   	tristate "MediaTek CMDQ Mailbox Support"
>   	depends on ARCH_MEDIATEK || COMPILE_TEST
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index 3c3c27d54c13..6b6dcc78d644 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -53,6 +53,8 @@ obj-$(CONFIG_STM32_IPCC) 	+= stm32-ipcc.o
>   
>   obj-$(CONFIG_MTK_ADSP_MBOX)	+= mtk-adsp-mailbox.o
>   
> +obj-$(CONFIG_MTK_APU_MBOX)	+= mtk-apu-mailbox.o
> +
>   obj-$(CONFIG_MTK_CMDQ_MBOX)	+= mtk-cmdq-mailbox.o
>   
>   obj-$(CONFIG_ZYNQMP_IPI_MBOX)	+= zynqmp-ipi-mailbox.o
> diff --git a/drivers/mailbox/mtk-apu-mailbox.c b/drivers/mailbox/mtk-apu-mailbox.c
> new file mode 100644
> index 000000000000..b347ebd34ef7
> --- /dev/null
> +++ b/drivers/mailbox/mtk-apu-mailbox.c
> @@ -0,0 +1,222 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024 MediaTek Inc.
> + */
> +
> +#include <asm/io.h>
> +#include <linux/bits.h>
> +#include <linux/interrupt.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/mailbox/mtk-apu-mailbox.h>
> +#include <linux/platform_device.h>
> +
> +#define INBOX		(0x0)
> +#define OUTBOX		(0x20)
> +#define INBOX_IRQ	(0xc0)
> +#define OUTBOX_IRQ	(0xc4)
> +#define INBOX_IRQ_MASK	(0xd0)
> +
> +#define SPARE_OFF_START	(0x40)
> +#define SPARE_OFF_END	(0xB0)
> +
> +struct mtk_apu_mailbox {
> +	struct device *dev;
> +	void __iomem *regs;
> +	struct mbox_controller controller;

struct mbox_controller mbox;

...it's shorter and consistent with at least other MTK mailbox drivers.

> +	u32 msgs[MSG_MBOX_SLOTS];

Just reuse struct mtk_apu_mailbox_msg instead.....

> +};
> +
> +struct mtk_apu_mailbox *g_mbox;

That global struct must disappear - and if you use the mailbox API correctly
it's even simple.

Also, you want something like....

static inline struct mtk_apu_mailbox *get_mtk_apu_mailbox(struct mbox_controller *mbox)
{
	return container_of(mbox, struct mtk_apu_mailbox, mbox);
}

> +
> +static irqreturn_t mtk_apu_mailbox_irq_top_half(int irq, void *dev_id)
> +{
static irqreturn_t mtk_apu_mailbox_irq(int irq, void *data)
{
	struct mbox_chan *chan = data;
	struct mtk_apu_mailbox = get_mtk_apu_mailbox(chan->mbox);

> +	struct mtk_apu_mailbox *mbox = dev_id;
> +	struct mbox_chan *link = &mbox->controller.chans[0];
> +	int i;
> +
> +	for (i = 0; i < MSG_MBOX_SLOTS; i++)
> +		mbox->msgs[i] = readl(mbox->regs + OUTBOX + i * sizeof(u32));
> +
> +	mbox_chan_received_data(link, &mbox->msgs);
> +
> +	return IRQ_WAKE_THREAD;
> +}
> +
> +static irqreturn_t mtk_apu_mailbox_irq_btm_half(int irq, void *dev_id)

....mtk_apu_mailbox_irq_thread(...)

> +{
> +	struct mtk_apu_mailbox *mbox = dev_id;
> +	struct mbox_chan *link = &mbox->controller.chans[0];
> +
> +	mbox_chan_received_data_bh(link, &mbox->msgs);

I don't think that you really need this _bh variant, looks more like you wanted
to have two callbacks instead of one.

You can instead have one callback and vary functionality based based on reading
a variable to decide what to actually do inside. Not a big deal.

> +	writel(readl(mbox->regs + OUTBOX_IRQ), mbox->regs + OUTBOX_IRQ);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int mtk_apu_mailbox_send_data(struct mbox_chan *chan, void *data)
> +{
> +	struct mtk_apu_mailbox *mbox = container_of(chan->mbox,
> +						    struct mtk_apu_mailbox,
> +						    controller);
> +	struct mtk_apu_mailbox_msg *msg = data;
> +	int i;
> +
> +	if (msg->send_cnt <= 0 || msg->send_cnt > MSG_MBOX_SLOTS) {
> +		dev_err(mbox->dev, "%s: invalid send_cnt %d\n", __func__, msg->send_cnt);
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 *	Mask lowest "send_cnt-1" interrupts bits, so the interrupt on the other side
> +	 *	triggers only after the last data slot is written (sent).
> +	 */
> +	writel(GENMASK(msg->send_cnt - 2, 0), mbox->regs + INBOX_IRQ_MASK);
> +	for (i = 0; i < msg->send_cnt; i++)
> +		writel(msg->data[i], mbox->regs + INBOX + i * sizeof(u32));
> +
> +	return 0;
> +}
> +
> +static bool mtk_apu_mailbox_last_tx_done(struct mbox_chan *chan)
> +{
> +	struct mtk_apu_mailbox *mbox = container_of(chan->mbox,
> +						    struct mtk_apu_mailbox,
> +						    controller);
> +
> +	return readl(mbox->regs + INBOX_IRQ) == 0;
> +}
> +
> +static const struct mbox_chan_ops mtk_apu_mailbox_ops = {
> +	.send_data = mtk_apu_mailbox_send_data,
> +	.last_tx_done = mtk_apu_mailbox_last_tx_done,
> +};
> +
> +/**
> + * mtk_apu_mbox_write - Write value to specifice mtk_apu_mbox spare register.
> + * @val: Value to be written.
> + * @offset: Offset of the spare register.
> + *
> + * Return: 0 if successful
> + *	   negative value if error happened
> + */
> +int mtk_apu_mbox_write(u32 val, u32 offset)
> +{
> +	if (!g_mbox) {
> +		pr_err("mtk apu mbox was not initialized, stop writing register\n");
> +		return -ENODEV;
> +	}
> +
> +	if (offset < SPARE_OFF_START || offset >= SPARE_OFF_END) {
> +		dev_err(g_mbox->dev, "Invalid offset %d for mtk apu mbox spare register\n", offset);
> +		return -EINVAL;
> +	}
> +
> +	writel(val, g_mbox->regs + offset);

There's something odd in what you're doing here, why would you ever need
a function that performs a writel just like that? What's the purpose?

What are you writing to the spare registers?
For which reason?

I think you can avoid (read this as: you *have to* avoid) having such a
function around.

> +	return 0;
> +}
> +EXPORT_SYMBOL_NS(mtk_apu_mbox_write, MTK_APU_MAILBOX);
> +
> +/**
> + * mtk_apu_mbox_read - Read value to specifice mtk_apu_mbox spare register.
> + * @offset: Offset of the spare register.
> + * @val: Pointer to store read value.
> + *
> + * Return: 0 if successful
> + *	   negative value if error happened
> + */
> +int mtk_apu_mbox_read(u32 offset, u32 *val)
> +{
> +	if (!g_mbox) {
> +		pr_err("mtk apu mbox was not initialized, stop reading register\n");
> +		return -ENODEV;
> +	}
> +
> +	if (offset < SPARE_OFF_START || offset >= SPARE_OFF_END) {
> +		dev_err(g_mbox->dev, "Invalid offset %d for mtk apu mbox spare register\n", offset);
> +		return -EINVAL;
> +	}
> +
> +	*val = readl(g_mbox->regs + offset);
> +

Same goes for this one.

> +	return 0;
> +}
> +EXPORT_SYMBOL_NS(mtk_apu_mbox_read, MTK_APU_MAILBOX);
> +
> +static int mtk_apu_mailbox_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mtk_apu_mailbox *mbox;
> +	int irq = -1, ret = 0;
> +
> +	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
> +	if (!mbox)
> +		return -ENOMEM;
> +
> +	mbox->dev = dev;
> +	platform_set_drvdata(pdev, mbox);
> +

Please move the platform_get_irq call here or anyway before registering the
mbox controller: in case anything goes wrong, devm won't have to unregister
the mbox afterwards because it never got registered in the first place.

> +	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(mbox->regs))
> +		return PTR_ERR(mbox->regs);
> +
> +	mbox->controller.txdone_irq = false;
> +	mbox->controller.txdone_poll = true;
> +	mbox->controller.txpoll_period = 1;
> +	mbox->controller.ops = &mtk_apu_mailbox_ops;
> +	mbox->controller.dev = dev;
> +	/*
> +	 * Here we only register 1 mbox channel.
> +	 * The remaining channels are used by other modules.

What other modules? I don't really see any - so please at least explain that in the
commit description.

> +	 */
> +	mbox->controller.num_chans = 1;
> +	mbox->controller.chans = devm_kcalloc(dev, mbox->controller.num_chans,
> +					      sizeof(*mbox->controller.chans),
> +					      GFP_KERNEL);
> +	if (!mbox->controller.chans)
> +		return -ENOMEM;
> +
> +	ret = devm_mbox_controller_register(dev, &mbox->controller);
> +	if (ret)
> +		return ret;
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	ret = devm_request_threaded_irq(dev, irq, mtk_apu_mailbox_irq_top_half,
> +					mtk_apu_mailbox_irq_btm_half, IRQF_ONESHOT,
> +					dev_name(dev), mbox);

pass mbox->chans to the isr

> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to request IRQ\n");
> +
> +	g_mbox = mbox;
> +
> +	dev_dbg(dev, "registered mtk apu mailbox\n");
> +
> +	return 0;
> +}
> +
> +static void mtk_apu_mailbox_remove(struct platform_device *pdev)
> +{
> +	g_mbox = NULL;
> +}
> +
> +static const struct of_device_id mtk_apu_mailbox_of_match[] = {
> +	{ .compatible = "mediatek,mt8188-apu-mailbox" },
> +	{ .compatible = "mediatek,mt8196-apu-mailbox" },

Just mediatek,mt8188-apu-mailbox is fine; you can allow mt8196==mt8188 in the
binding instead.

> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mtk_apu_mailbox_of_match);
> +
> +static struct platform_driver mtk_apu_mailbox_driver = {
> +	.probe = mtk_apu_mailbox_probe,
> +	.remove = mtk_apu_mailbox_remove,

You don't need this remove callback, since g_mbox has to disappear :-)

> +	.driver = {
> +		.name = "mtk-apu-mailbox",
> +		.of_match_table = mtk_apu_mailbox_of_match,
> +	},
> +};
> +
> +module_platform_driver(mtk_apu_mailbox_driver);
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("MediaTek APU Mailbox Driver");
> diff --git a/include/linux/mailbox/mtk-apu-mailbox.h b/include/linux/mailbox/mtk-apu-mailbox.h
> new file mode 100644
> index 000000000000..d1457d16ce9b
> --- /dev/null
> +++ b/include/linux/mailbox/mtk-apu-mailbox.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2024 MediaTek Inc.
> + *
> + */
> +
> +#ifndef __MTK_APU_MAILBOX_H__
> +#define __MTK_APU_MAILBOX_H__
> +
> +#define MSG_MBOX_SLOTS	(8)
> +
> +struct mtk_apu_mailbox_msg {
> +	int send_cnt;

u8 data_cnt;

> +	u32 data[MSG_MBOX_SLOTS];

With hardcoded slots, what happens when we get a new chip in the future that
supports more slots?

Please think about this now and make the implementation flexible before that
happens because, at a later time, it'll be harder.

Regards,
Angelo

> +};
> +
> +int mtk_apu_mbox_write(u32 val, u32 offset);
> +int mtk_apu_mbox_read(u32 offset, u32 *val);
> +
> +#endif /* __MTK_APU_MAILBOX_H__ */