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Message-ID:
<TYZPR06MB656881C7D0CB77C9051149C9F17BA@TYZPR06MB6568.apcprd06.prod.outlook.com>
Date: Wed, 25 Jun 2025 03:05:43 +0000
From: Jammy Huang <jammy_huang@...eedtech.com>
To: Andrew Jeffery <andrew@...econstruct.com.au>, "jassisinghbrar@...il.com"
<jassisinghbrar@...il.com>, "robh@...nel.org" <robh@...nel.org>,
"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org"
<conor+dt@...nel.org>, "joel@....id.au" <joel@....id.au>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-aspeed@...ts.ozlabs.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?
Agree.
>
> > +#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.
Agree.
>
> > +
> > + 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.
OK.
>
> > +}
> > +
> > +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);
>
OK, I will let ast2700_mbox_tx_done return bool to simplify it.
> > +}
> > +
> > +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?
OK.
>
> > + 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.c
> hans),
> > +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?
Agree.
>
> 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");
Best Regards
Jammy
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