[PATCH 2/7] soc: aspeed: Introduce core eSPI controller support

[aspeedyh <yh_chung@aspeedtech.com>]

Add core eSPI controller support and common code for ASPEED SoCs. The
eSPI engine is a slave device in BMC to communicate with the Host over
the eSPI interface.

The initial support includes basic eSPI driver probe/remove operations,
and provides operators for ASPEED SoCs to implement their own eSPI slave
device drivers that are different among SoC models.

Signed-off-by: aspeedyh <yh_chung@aspeedtech.com>
---
 drivers/soc/aspeed/Kconfig            |   7 ++
 drivers/soc/aspeed/Makefile           |   1 +
 drivers/soc/aspeed/espi/Makefile      |   1 +
 drivers/soc/aspeed/espi/aspeed-espi.c | 143 ++++++++++++++++++++++++++++++++++
 drivers/soc/aspeed/espi/aspeed-espi.h |  27 +++++++
 5 files changed, 179 insertions(+)

diff --git a/drivers/soc/aspeed/Kconfig b/drivers/soc/aspeed/Kconfig
index f579ee0b5afa..677812fab11a 100644
--- a/drivers/soc/aspeed/Kconfig
+++ b/drivers/soc/aspeed/Kconfig
@@ -52,6 +52,13 @@ config ASPEED_SOCINFO
 	help
 	  Say yes to support decoding of ASPEED BMC information.
 
+config ASPEED_ESPI
+	tristate "ASPEED eSPI slave driver"
+	help
+	  Enable driver support for Aspeed eSPI controller. The eSPI controller
+	  plays as a slave device in BMC to communicate with the Host over the
+	  eSPI interface using peripheral, virtual wire, out of band, and flash
+	  channels.
 endmenu
 
 endif
diff --git a/drivers/soc/aspeed/Makefile b/drivers/soc/aspeed/Makefile
index b35d74592964..79d794de428a 100644
--- a/drivers/soc/aspeed/Makefile
+++ b/drivers/soc/aspeed/Makefile
@@ -4,3 +4,4 @@ obj-$(CONFIG_ASPEED_LPC_SNOOP)		+= aspeed-lpc-snoop.o
 obj-$(CONFIG_ASPEED_UART_ROUTING)	+= aspeed-uart-routing.o
 obj-$(CONFIG_ASPEED_P2A_CTRL)		+= aspeed-p2a-ctrl.o
 obj-$(CONFIG_ASPEED_SOCINFO)		+= aspeed-socinfo.o
+obj-$(CONFIG_ASPEED_ESPI)		+= espi/
diff --git a/drivers/soc/aspeed/espi/Makefile b/drivers/soc/aspeed/espi/Makefile
new file mode 100644
index 000000000000..d96dc030e23b
--- /dev/null
+++ b/drivers/soc/aspeed/espi/Makefile
@@ -0,0 +1 @@
+obj-y += aspeed-espi.o
diff --git a/drivers/soc/aspeed/espi/aspeed-espi.c b/drivers/soc/aspeed/espi/aspeed-espi.c
new file mode 100644
index 000000000000..15d58b38bbe4
--- /dev/null
+++ b/drivers/soc/aspeed/espi/aspeed-espi.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Unified Aspeed eSPI driver framework for different generation SoCs
+ */
+
+#include <linux/clk.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+
+#include "aspeed-espi.h"
+
+struct aspeed_espi_ops {
+	void (*espi_pre_init)(struct aspeed_espi *espi);
+	void (*espi_post_init)(struct aspeed_espi *espi);
+	void (*espi_deinit)(struct aspeed_espi *espi);
+	irqreturn_t (*espi_isr)(int irq, void *espi);
+};
+
+static const struct of_device_id aspeed_espi_of_matches[] = {
+	{ }
+};
+MODULE_DEVICE_TABLE(of, aspeed_espi_of_matches);
+
+static int aspeed_espi_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *match;
+	struct aspeed_espi *espi;
+	struct resource *res;
+	struct device *dev;
+	int rc;
+
+	dev = &pdev->dev;
+	espi = devm_kzalloc(dev, sizeof(*espi), GFP_KERNEL);
+	if (!espi)
+		return -ENOMEM;
+
+	espi->dev = dev;
+	match = of_match_device(aspeed_espi_of_matches, dev);
+	if (!match)
+		return -ENODEV;
+
+	espi->pdev = pdev;
+	espi->ops = match->data;
+	if (!espi->ops || !espi->ops->espi_isr)
+		return -EINVAL;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(dev, "cannot get resource\n");
+		return -ENODEV;
+	}
+
+	espi->regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(espi->regs)) {
+		dev_err(dev, "cannot map registers\n");
+		return PTR_ERR(espi->regs);
+	}
+
+	espi->irq = platform_get_irq(pdev, 0);
+	if (espi->irq < 0) {
+		dev_err(dev, "cannot get IRQ number\n");
+		return espi->irq;
+	}
+
+	espi->rst = devm_reset_control_get_optional(dev, NULL);
+	if (IS_ERR(espi->rst)) {
+		dev_err(dev, "cannot get reset control\n");
+		return PTR_ERR(espi->rst);
+	}
+
+	espi->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(espi->clk)) {
+		dev_err(dev, "cannot get clock control\n");
+		return PTR_ERR(espi->clk);
+	}
+
+	rc = clk_prepare_enable(espi->clk);
+	if (rc) {
+		dev_err(dev, "cannot enable clocks\n");
+		return rc;
+	}
+
+	if (espi->ops->espi_pre_init)
+		espi->ops->espi_pre_init(espi);
+
+	rc = devm_request_irq(dev, espi->irq, espi->ops->espi_isr, 0,
+			      dev_name(dev), espi);
+	if (rc) {
+		dev_err(dev, "cannot request IRQ\n");
+		goto err_deinit;
+	}
+
+	if (espi->ops->espi_post_init)
+		espi->ops->espi_post_init(espi);
+
+	platform_set_drvdata(pdev, espi);
+
+	dev_info(dev, "module loaded\n");
+
+	return 0;
+
+err_deinit:
+	if (espi->ops->espi_deinit)
+		espi->ops->espi_deinit(espi);
+	clk_disable_unprepare(espi->clk);
+
+	return rc;
+}
+
+static void aspeed_espi_remove(struct platform_device *pdev)
+{
+	struct aspeed_espi *espi;
+
+	espi = platform_get_drvdata(pdev);
+
+	if (!espi)
+		return;
+
+	if (espi->ops->espi_deinit)
+		espi->ops->espi_deinit(espi);
+
+	clk_disable_unprepare(espi->clk);
+}
+
+static struct platform_driver aspeed_espi_driver = {
+	.driver = {
+		.name = "aspeed-espi",
+		.of_match_table = aspeed_espi_of_matches,
+	},
+	.probe = aspeed_espi_probe,
+	.remove = aspeed_espi_remove,
+};
+
+module_platform_driver(aspeed_espi_driver);
+
+MODULE_AUTHOR("Aspeed Technology Inc.");
+MODULE_DESCRIPTION("Aspeed eSPI controller");
+MODULE_LICENSE("GPL");
diff --git a/drivers/soc/aspeed/espi/aspeed-espi.h b/drivers/soc/aspeed/espi/aspeed-espi.h
new file mode 100644
index 000000000000..f4ad7f61fef6
--- /dev/null
+++ b/drivers/soc/aspeed/espi/aspeed-espi.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Unified eSPI driver header file and data structures
+ * Copyright 2026 Aspeed Technology Inc.
+ */
+#ifndef ASPEED_ESPI_H
+#define ASPEED_ESPI_H
+
+#include <linux/irqreturn.h>
+#include <linux/miscdevice.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#define DEVICE_NAME		"aspeed-espi"
+
+struct aspeed_espi {
+	struct platform_device *pdev;
+	struct device *dev;
+	void __iomem *regs;
+	struct reset_control *rst;
+	struct clk *clk;
+	int dev_id;
+	int irq;
+	const struct aspeed_espi_ops *ops;
+};
+
+#endif

-- 
2.34.1