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Message-ID: <c1820a08930576d19c107d8e007acb21cae07a4d.camel@codeconstruct.com.au>
Date: Wed, 25 Jun 2025 10:42:40 +0930
From: Andrew Jeffery <andrew@...econstruct.com.au>
To: Jammy Huang <jammy_huang@...eedtech.com>, jassisinghbrar@...il.com,
robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, joel@....id.au,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org
Subject: Re: [PATCH v4 2/2] mailbox: aspeed: add mailbox driver for AST27XX
series SoC
On Mon, 2025-06-23 at 10:44 +0800, Jammy Huang wrote:
> Add mailbox controller driver for AST27XX SoCs, which provides
> independent tx/rx mailbox between different processors. There are 4
> channels for each tx/rx mailbox and each channel has an 32-byte FIFO.
>
> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
> ---
> drivers/mailbox/Kconfig | 8 ++
> drivers/mailbox/Makefile | 2 +
> drivers/mailbox/ast2700-mailbox.c | 230 ++++++++++++++++++++++++++++++
> 3 files changed, 240 insertions(+)
> create mode 100644 drivers/mailbox/ast2700-mailbox.c
>
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index 68eeed660a4a..1c38cd570091 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -340,4 +340,12 @@ config THEAD_TH1520_MBOX
> kernel is running, and E902 core used for power management among other
> things.
>
> +config AST2700_MBOX
> + tristate "ASPEED AST2700 IPC driver"
> + depends on ARCH_ASPEED || COMPILE_TEST
> + help
> + Mailbox driver implementation for ASPEED AST27XX SoCs. This driver
> + can be used to send message between different processors in SoC.
> + The driver provides mailbox support for sending interrupts to the
> + clients. Say Y here if you want to build this driver.
> endif
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index 13a3448b3271..9a9add9a7548 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -72,3 +72,5 @@ obj-$(CONFIG_QCOM_CPUCP_MBOX) += qcom-cpucp-mbox.o
> obj-$(CONFIG_QCOM_IPCC) += qcom-ipcc.o
>
> obj-$(CONFIG_THEAD_TH1520_MBOX) += mailbox-th1520.o
> +
> +obj-$(CONFIG_AST2700_MBOX) += ast2700-mailbox.o
> diff --git a/drivers/mailbox/ast2700-mailbox.c b/drivers/mailbox/ast2700-mailbox.c
> new file mode 100644
> index 000000000000..64638ac67e7a
> --- /dev/null
> +++ b/drivers/mailbox/ast2700-mailbox.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright Aspeed Technology Inc. (C) 2025. All rights reserved
> + */
> +
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +/* Each bit in the register represents an IPC ID */
> +#define IPCR_TX_TRIG 0x00
> +#define IPCR_TX_ENABLE 0x04
> +#define IPCR_RX_ENABLE 0x104
> +#define IPCR_TX_STATUS 0x08
> +#define IPCR_RX_STATUS 0x108
> +#define RX_IRQ(n) BIT(0 + 1 * (n))
Seems overly complex?
> +#define RX_IRQ_MASK 0xf
> +#define IPCR_TX_DATA 0x10
> +#define IPCR_RX_DATA 0x110
> +
> +struct ast2700_mbox_data {
> + u8 num_chans;
> + u8 msg_size;
> +};
> +
> +struct ast2700_mbox {
> + struct mbox_controller mbox;
> + const struct ast2700_mbox_data *drv_data;
> + void __iomem *regs;
> +};
> +
> +static inline int ch_num(struct mbox_chan *chan)
> +{
> + return chan - chan->mbox->chans;
> +}
> +
> +static inline int ast2700_mbox_tx_done(struct ast2700_mbox *mb, int idx)
> +{
> + return !(readl(mb->regs + IPCR_TX_STATUS) & BIT(idx));
> +}
> +
> +static irqreturn_t ast2700_mbox_irq(int irq, void *p)
> +{
> + struct ast2700_mbox *mb = p;
> + void __iomem *data_reg;
> + int num_words;
> + u32 *word_data;
> + u32 status;
> + int n;
> +
> + /* Only examine channels that are currently enabled. */
> + status = readl(mb->regs + IPCR_RX_ENABLE) &
> + readl(mb->regs + IPCR_RX_STATUS);
> +
> + if (!(status & RX_IRQ_MASK))
> + return IRQ_NONE;
> +
> + for (n = 0; n < mb->mbox.num_chans; ++n) {
> + struct mbox_chan *chan = &mb->mbox.chans[n];
> +
> + if (!(status & RX_IRQ(n)))
> + continue;
> +
> + /* Read the message data */
> + for (data_reg = mb->regs + IPCR_RX_DATA + mb->drv_data->msg_size * n,
> + word_data = chan->con_priv,
> + num_words = (mb->drv_data->msg_size / sizeof(u32));
> + num_words;
> + num_words--, data_reg += sizeof(u32), word_data++)
> + *word_data = readl(data_reg);
> +
> + mbox_chan_received_data(chan, chan->con_priv);
> +
> + /* The IRQ can be cleared only once the FIFO is empty. */
> + writel(RX_IRQ(n), mb->regs + IPCR_RX_STATUS);
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int ast2700_mbox_send_data(struct mbox_chan *chan, void *data)
> +{
> + struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
> + void __iomem *data_reg;
> + u32 *word_data;
> + int num_words;
> + int idx = ch_num(chan);
> +
> + if (!(readl(mb->regs + IPCR_TX_ENABLE) & BIT(idx))) {
> + dev_warn(mb->mbox.dev, "%s: Ch-%d not enabled yet\n", __func__, idx);
> + return -EBUSY;
> + }
> +
> + if (!(ast2700_mbox_tx_done(mb, idx))) {
> + dev_warn(mb->mbox.dev, "%s: Ch-%d last data has not finished\n", __func__, idx);
> + return -EBUSY;
> + }
> +
> + /* Write the message data */
> + for (data_reg = mb->regs + IPCR_TX_DATA + mb->drv_data->msg_size * idx,
> + word_data = (u32 *)data,
> + num_words = (mb->drv_data->msg_size / sizeof(u32));
> + num_words;
> + num_words--, data_reg += sizeof(u32), word_data++)
> + writel(*word_data, data_reg);
> +
> + writel(BIT(idx), mb->regs + IPCR_TX_TRIG);
> + dev_dbg(mb->mbox.dev, "%s: Ch-%d sent\n", __func__, idx);
> +
> + return 0;
> +}
> +
> +static int ast2700_mbox_startup(struct mbox_chan *chan)
> +{
> + struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
> + int idx = ch_num(chan);
> + void __iomem *reg = mb->regs + IPCR_RX_ENABLE;
> +
> + writel(readl(reg) | BIT(idx), reg);
It seems ->startup is called with the channel spinlock held, but as
each channel is independent, the RMW sequence here could lead to
unexpected results?
I expect you need a spinlock to protect against concurrent changes to
channel state.
> +
> + return 0;
> +}
> +
> +static void ast2700_mbox_shutdown(struct mbox_chan *chan)
> +{
> + struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
> + int idx = ch_num(chan);
> + void __iomem *reg = mb->regs + IPCR_RX_ENABLE;
> +
> + writel(readl(reg) & ~BIT(idx), reg);
See comment above.
> +}
> +
> +static bool ast2700_mbox_last_tx_done(struct mbox_chan *chan)
> +{
> + struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
> + int idx = ch_num(chan);
> +
> + return ast2700_mbox_tx_done(mb, idx) ? true : false;
The ternary expression is unnecessary, we can instead do:
return !!ast2700_mbox_tx_done(mb, idx);
> +}
> +
> +static const struct mbox_chan_ops ast2700_mbox_chan_ops = {
> + .send_data = ast2700_mbox_send_data,
> + .startup = ast2700_mbox_startup,
> + .shutdown = ast2700_mbox_shutdown,
> + .last_tx_done = ast2700_mbox_last_tx_done,
> +};
> +
> +static int ast2700_mbox_probe(struct platform_device *pdev)
> +{
> + struct ast2700_mbox *mb;
> + const struct ast2700_mbox_data *drv_data;
Calling this drv_data is slightly confusing. Perhaps dev_data?
> + struct device *dev = &pdev->dev;
> + int irq, ret;
> +
> + if (!pdev->dev.of_node)
> + return -ENODEV;
> +
> + drv_data = device_get_match_data(&pdev->dev);
> +
> + mb = devm_kzalloc(dev, sizeof(*mb), GFP_KERNEL);
> + if (!mb)
> + return -ENOMEM;
> +
> + mb->mbox.chans = devm_kcalloc(&pdev->dev, drv_data->num_chans,
> + sizeof(*mb->mbox.chans), GFP_KERNEL);
> + if (!mb->mbox.chans)
> + return -ENOMEM;
> +
> + /* con_priv of each channel is used to store the message received */
> + for (int i = 0; i < drv_data->num_chans; i++) {
> + mb->mbox.chans[i].con_priv = devm_kcalloc(dev, drv_data->msg_size,
> + sizeof(u8), GFP_KERNEL);
> + if (!mb->mbox.chans[i].con_priv)
> + return -ENOMEM;
> + }
> +
> + platform_set_drvdata(pdev, mb);
> +
> + mb->regs = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(mb->regs))
> + return PTR_ERR(mb->regs);
> +
> + mb->drv_data = drv_data;
> + mb->mbox.dev = dev;
> + mb->mbox.num_chans = drv_data->num_chans;
> + mb->mbox.ops = &ast2700_mbox_chan_ops;
> + mb->mbox.txdone_irq = false;
> + mb->mbox.txdone_poll = true;
> + mb->mbox.txpoll_period = 5;
> +
> + irq = platform_get_irq(pdev, 0);
> + if (irq < 0)
> + return irq;
> +
> + ret = devm_request_irq(dev, irq, ast2700_mbox_irq, 0, dev_name(dev), mb);
> + if (ret)
> + return ret;
> +
> + return devm_mbox_controller_register(dev, &mb->mbox);
> +}
> +
> +static const struct ast2700_mbox_data ast2700_drv_data = {
Again, this is data about the device, not data about the driver.
Perhaps ast2700_dev_data?
Andrew
> + .num_chans = 4,
> + .msg_size = 0x20,
> +};
> +
> +static const struct of_device_id ast2700_mbox_of_match[] = {
> + { .compatible = "aspeed,ast2700-mailbox", .data = &ast2700_drv_data },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, ast2700_mbox_of_match);
> +
> +static struct platform_driver ast2700_mbox_driver = {
> + .driver = {
> + .name = "ast2700-mailbox",
> + .of_match_table = ast2700_mbox_of_match,
> + },
> + .probe = ast2700_mbox_probe,
> +};
> +module_platform_driver(ast2700_mbox_driver);
> +
> +MODULE_AUTHOR("Jammy Huang <jammy_huang@...eedtech.com>");
> +MODULE_DESCRIPTION("ASPEED AST2700 IPC driver");
> +MODULE_LICENSE("GPL");
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