On Wed, 2025-06-25 at 15:34 +0800, Jammy Huang wrote:

quoted

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 <redacted>
---
 drivers/mailbox/Kconfig           |   8 +
 drivers/mailbox/Makefile          |   2 +
 drivers/mailbox/ast2700-mailbox.c | 240
++++++++++++++++++++++++++++++
 3 files changed, 250 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

quoted

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

quoted

+driver
+         can be used to send message between different processors in

SoC.

quoted

+         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

quoted

 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..5470053f8139

--- /dev/null
+++ b/drivers/mailbox/ast2700-mailbox.c

@@ -0,0 +1,240 @@
+// 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_ENABLE            0x04

quoted

+#define IPCR_STATUS            0x08

#define  RX_IRQ(n)

quoted

+BIT(n) #define  RX_IRQ_MASK           0xf #define

IPCR_DATA

quoted

+0x10
+
+struct ast2700_mbox_data {
+       u8 num_chans;
+       u8 msg_size;
+};
+
+struct ast2700_mbox {
+       struct mbox_controller mbox;
+       u8 msg_size;
+       void __iomem *tx_regs;
+       void __iomem *rx_regs;
+       spinlock_t lock;
+};
+
+static inline int ch_num(struct mbox_chan *chan) {
+       return chan - chan->mbox->chans; }
+
+static inline bool ast2700_mbox_tx_done(struct ast2700_mbox *mb, int
+idx) {
+       return !(readl(mb->tx_regs + IPCR_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->rx_regs + IPCR_ENABLE) &
+                readl(mb->rx_regs + IPCR_STATUS);

Also need to lock over these reads to handle concurrent startup/shutdown?

It read-only here. I think it's fine.

quoted

+
+       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->rx_regs + IPCR_DATA +

mb->msg_size

quoted

+* n,
+                    word_data = chan->con_priv,
+                    num_words = (mb->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.

quoted

+*/
+               writel(RX_IRQ(n), mb->rx_regs + IPCR_STATUS);

Can we rather clear the status once outside the loop immediately before
return?

writel(status, mb->rx_regs + IPCR_STATUS);

I think it's better to keep current way. Because tx side could polling check rx-status
to know if tx is done. mbox_chan_received_data() here will invoke the callback registered
by mailbox-client. It could take times depending on how the callback is implemented.
Since we have 4 channels now, clear it earlier can have better performance.

quoted

+       }
+
+       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);

quoted

+       void __iomem *data_reg;
+       u32 *word_data;
+       int num_words;
+       int idx = ch_num(chan);
+
+       if (!(readl(mb->tx_regs + IPCR_ENABLE) & BIT(idx))) {
+               dev_warn(mb->mbox.dev, "%s: Ch-%d not enabled

yet\n",

quoted

+__func__, idx);
+               return -EBUSY;

-ENODEV? I wouldn't say it's busy here :)

quoted

+       }
+
+       if (!(ast2700_mbox_tx_done(mb, idx))) {
+               dev_warn(mb->mbox.dev, "%s: Ch-%d last data has

not

quoted

+finished\n", __func__, idx);
+               return -EBUSY;
+       }
+
+       /* Write the message data */
+       for (data_reg = mb->tx_regs + IPCR_DATA + mb->msg_size * idx,
+            word_data = (u32 *)data,
+            num_words = (mb->msg_size / sizeof(u32));
+            num_words;
+            num_words--, data_reg += sizeof(u32), word_data++)
+               writel(*word_data, data_reg);
+
+       writel(BIT(idx), mb->tx_regs + IPCR_TX_TRIG);
+       dev_dbg(mb->mbox.dev, "%s: Ch-%d sent\n", __func__, idx);
+
+       return 0;
+}
+

*snip*

quoted

+
+static int ast2700_mbox_probe(struct platform_device *pdev) {
+       struct ast2700_mbox *mb;
+       const struct ast2700_mbox_data *dev_data;
+       struct device *dev = &pdev->dev;
+       int irq, ret;
+
+       if (!pdev->dev.of_node)
+               return -ENODEV;
+
+       dev_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,

dev_data->num_chans,

quoted

+                                     sizeof(*mb->mbox.c
hans),

quoted

+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 < dev_data->num_chans; i++) {
+               mb->mbox.chans[i].con_priv = devm_kcalloc(dev,
+dev_data->msg_size,

+
       sizeof(u8),

quoted

+GFP_KERNEL);
+               if (!mb->mbox.chans[i].con_priv)
+                       return -ENOMEM;
+       }
+
+       platform_set_drvdata(pdev, mb);
+
+       mb->tx_regs = devm_platform_ioremap_resource(pdev, 0);

See the thought about reg-names on the binding.

Agree.

Andrew

Regards
Jammy