i2c: amd-asf: Add ACPI support for AMD ASF Controller

The AMD ASF controller is presented to the operating system as an ACPI
device. The AMD ASF driver can use ACPI to obtain information about the
ASF controller's attributes, such as the ASF address space and interrupt
number, and to handle ASF interrupts.

Currently, the piix4 driver assumes that a specific port address is
designated for AUX operations. However, with the introduction of ASF, the
same port address may also be used by the ASF controller. Therefore, a
check needs to be added to ensure that if ASF is advertised and enabled in
ACPI, the AUX port should not be configured.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Co-developed-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

drivers/i2c/busses/Kconfig

@@ -95,6 +95,22 @@ config I2C_AMD_MP2
 	  This driver can also be built as modules.  If so, the modules will
 	  be called i2c-amd-mp2-pci and i2c-amd-mp2-plat.
 
+config I2C_AMD_ASF
+	tristate "AMD ASF I2C Controller Support"
+	depends on I2C_PIIX4
+	help
+	  This option enables support for the AMD ASF (Alert Standard Format)
+	  I2C controller. The AMD ASF controller is an SMBus controller with
+	  built-in ASF functionality, allowing it to issue generic SMBus
+	  packets and communicate with the DASH controller using MCTP over
+	  ASF.
+
+	  If you have an AMD system with ASF support and want to enable this
+	  functionality, say Y or M here. If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called i2c_amd_asf_plat.
+
 config I2C_HIX5HD2
 	tristate "Hix5hd2 high-speed I2C driver"
 	depends on ARCH_HISI || ARCH_HIX5HD2 || COMPILE_TEST

drivers/i2c/busses/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
 # Embedded system I2C/SMBus host controller drivers
 obj-$(CONFIG_I2C_ALTERA)	+= i2c-altera.o
 obj-$(CONFIG_I2C_AMD_MP2)	+= i2c-amd-mp2-pci.o i2c-amd-mp2-plat.o
+obj-$(CONFIG_I2C_AMD_ASF)	+= i2c-amd-asf-plat.o
 obj-$(CONFIG_I2C_ASPEED)	+= i2c-aspeed.o
 obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 i2c-at91-objs			:= i2c-at91-core.o i2c-at91-master.o

drivers/i2c/busses/i2c-amd-asf-plat.c

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AMD Alert Standard Format Platform Driver
+ *
+ * Copyright (c) 2024, Advanced Micro Devices, Inc.
+ * All Rights Reserved.
+ *
+ * Authors: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
+ *	    Sanket Goswami <Sanket.Goswami@amd.com>
+ */
+
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/gfp_types.h>
+#include <linux/i2c.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/sprintf.h>
+
+#include "i2c-piix4.h"
+
+struct amd_asf_dev {
+	struct i2c_adapter adap;
+	struct sb800_mmio_cfg mmio_cfg;
+	struct resource *port_addr;
+};
+
+static int amd_asf_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct amd_asf_dev *asf_dev;
+
+	asf_dev = devm_kzalloc(dev, sizeof(*asf_dev), GFP_KERNEL);
+	if (!asf_dev)
+		return dev_err_probe(dev, -ENOMEM, "Failed to allocate memory\n");
+
+	asf_dev->mmio_cfg.use_mmio = true;
+	asf_dev->port_addr = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (!asf_dev->port_addr)
+		return dev_err_probe(dev, -EINVAL, "missing IO resources\n");
+
+	asf_dev->adap.owner = THIS_MODULE;
+	asf_dev->adap.dev.parent = dev;
+
+	i2c_set_adapdata(&asf_dev->adap, asf_dev);
+	snprintf(asf_dev->adap.name, sizeof(asf_dev->adap.name), "AMD ASF adapter");
+
+	return devm_i2c_add_adapter(dev, &asf_dev->adap);
+}
+
+static const struct acpi_device_id amd_asf_acpi_ids[] = {
+	{ "AMDI001A" },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, amd_asf_acpi_ids);
+
+static struct platform_driver amd_asf_driver = {
+	.driver = {
+		.name = "i2c-amd-asf",
+		.acpi_match_table = amd_asf_acpi_ids,
+	},
+	.probe = amd_asf_probe,
+};
+module_platform_driver(amd_asf_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("AMD Alert Standard Format Driver");

drivers/i2c/busses/i2c-piix4.c

@@ -87,6 +87,7 @@
 
 #define SB800_PIIX4_FCH_PM_ADDR			0xFED80300
 #define SB800_PIIX4_FCH_PM_SIZE			8
+#define SB800_ASF_ACPI_PATH			"\\_SB.ASFC"
 
 /* insmod parameters */
 
@@ -1024,6 +1025,9 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
 	int retval;
 	bool is_sb800 = false;
+	bool is_asf = false;
+	acpi_status status;
+	acpi_handle handle;
 
 	if ((dev->vendor == PCI_VENDOR_ID_ATI &&
 	     dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
@@ -1086,10 +1090,16 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
 		}
 	}
 
+	status = acpi_get_handle(NULL, (acpi_string)SB800_ASF_ACPI_PATH, &handle);
+	if (ACPI_SUCCESS(status))
+		is_asf = true;
+
 	if (dev->vendor == PCI_VENDOR_ID_AMD &&
 	    (dev->device == PCI_DEVICE_ID_AMD_HUDSON2_SMBUS ||
 	     dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS)) {
-		retval = piix4_setup_sb800(dev, id, 1);
+		/* Do not setup AUX port if ASF is enabled */
+		if (!is_asf)
+			retval = piix4_setup_sb800(dev, id, 1);
 	}
 
 	if (retval > 0) {