[PATCH net-next v7 3/7] arch: x86: add IPC mailbox accessor function and add SoC register access

[Choong Yong Liang <yong.liang.choong@linux.intel.com>]

From: "David E. Box" <david.e.box@linux.intel.com>

- Exports intel_pmc_ipc() for host access to the PMC IPC mailbox
- Add support to use IPC command allows host to access SoC registers
through PMC firmware that are otherwise inaccessible to the host due to
security policies.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Chao Qin <chao.qin@intel.com>
Signed-off-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
---
 MAINTAINERS                                   |  2 +
 arch/x86/Kconfig                              |  9 +++
 arch/x86/platform/intel/Makefile              |  1 +
 arch/x86/platform/intel/pmc_ipc.c             | 75 +++++++++++++++++++
 .../linux/platform_data/x86/intel_pmc_ipc.h   | 34 +++++++++
 5 files changed, 121 insertions(+)
 create mode 100644 arch/x86/platform/intel/pmc_ipc.c
 create mode 100644 include/linux/platform_data/x86/intel_pmc_ipc.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d1086e53a317..7a0681f83449 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11862,8 +11862,10 @@ M:	Rajneesh Bhardwaj <irenic.rajneesh@gmail.com>
 M:	David E Box <david.e.box@intel.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
+F:	arch/x86/platform/intel/pmc_ipc.c
 F:	Documentation/ABI/testing/sysfs-platform-intel-pmc
 F:	drivers/platform/x86/intel/pmc/
+F:	linux/platform_data/x86/intel_pmc_ipc.h
 
 INTEL PMIC GPIO DRIVERS
 M:	Andy Shevchenko <andy@kernel.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 87198d957e2f..631c1f10776c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -688,6 +688,15 @@ config X86_AMD_PLATFORM_DEVICE
 	  I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
 	  implemented under PINCTRL subsystem.
 
+config INTEL_PMC_IPC
+	tristate "Intel Core SoC Power Management Controller IPC mailbox"
+	depends on ACPI
+	help
+	  This option enables sideband register access support for Intel SoC
+	  power management controller IPC mailbox.
+
+	  If you don't require the option or are in doubt, say N.
+
 config IOSF_MBI
 	tristate "Intel SoC IOSF Sideband support for SoC platforms"
 	depends on PCI
diff --git a/arch/x86/platform/intel/Makefile b/arch/x86/platform/intel/Makefile
index dbee3b00f9d0..2f1805556d0c 100644
--- a/arch/x86/platform/intel/Makefile
+++ b/arch/x86/platform/intel/Makefile
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_IOSF_MBI)			+= iosf_mbi.o
+obj-$(CONFIG_INTEL_PMC_IPC)		+= pmc_ipc.o
diff --git a/arch/x86/platform/intel/pmc_ipc.c b/arch/x86/platform/intel/pmc_ipc.c
new file mode 100644
index 000000000000..a96234982710
--- /dev/null
+++ b/arch/x86/platform/intel/pmc_ipc.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Intel Core SoC Power Management Controller IPC mailbox
+ *
+ * Copyright (c) 2023, Intel Corporation.
+ * All Rights Reserved.
+ *
+ * Authors: Choong Yong Liang <yong.liang.choong@linux.intel.com>
+ *          David E. Box <david.e.box@linux.intel.com>
+ */
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/platform_data/x86/intel_pmc_ipc.h>
+
+#define PMC_IPCS_PARAM_COUNT           7
+
+int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, u32 *rbuf)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object params[PMC_IPCS_PARAM_COUNT] = {
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+		{.type = ACPI_TYPE_INTEGER,},
+	};
+	struct acpi_object_list arg_list = { PMC_IPCS_PARAM_COUNT, params };
+	union acpi_object *obj;
+	int status;
+
+	if (!ipc_cmd || !rbuf)
+		return -EINVAL;
+
+	/*
+	 * 0: IPC Command
+	 * 1: IPC Sub Command
+	 * 2: Size
+	 * 3-6: Write Buffer for offset
+	 */
+	params[0].integer.value = ipc_cmd->cmd;
+	params[1].integer.value = ipc_cmd->sub_cmd;
+	params[2].integer.value = ipc_cmd->size;
+	params[3].integer.value = ipc_cmd->wbuf[0];
+	params[4].integer.value = ipc_cmd->wbuf[1];
+	params[5].integer.value = ipc_cmd->wbuf[2];
+	params[6].integer.value = ipc_cmd->wbuf[3];
+
+	status = acpi_evaluate_object(NULL, "\\IPCS", &arg_list, &buffer);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	obj = buffer.pointer;
+	/* Check if the number of elements in package is 5 */
+	if (obj && obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+		const union acpi_object *objs = obj->package.elements;
+
+		if ((u8)objs[0].integer.value != 0)
+			return -EINVAL;
+
+		rbuf[0] = objs[1].integer.value;
+		rbuf[1] = objs[2].integer.value;
+		rbuf[2] = objs[3].integer.value;
+		rbuf[3] = objs[4].integer.value;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(intel_pmc_ipc);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Intel PMC IPC Mailbox accessor");
diff --git a/include/linux/platform_data/x86/intel_pmc_ipc.h b/include/linux/platform_data/x86/intel_pmc_ipc.h
new file mode 100644
index 000000000000..d47b89f873fc
--- /dev/null
+++ b/include/linux/platform_data/x86/intel_pmc_ipc.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Intel Core SoC Power Management Controller Header File
+ *
+ * Copyright (c) 2023, Intel Corporation.
+ * All Rights Reserved.
+ *
+ * Authors: Choong Yong Liang <yong.liang.choong@linux.intel.com>
+ *          David E. Box <david.e.box@linux.intel.com>
+ */
+#ifndef INTEL_PMC_IPC_H
+#define INTEL_PMC_IPC_H
+
+#define IPC_SOC_REGISTER_ACCESS			0xAA
+#define IPC_SOC_SUB_CMD_READ			0x00
+#define IPC_SOC_SUB_CMD_WRITE			0x01
+
+struct pmc_ipc_cmd {
+	u32 cmd;
+	u32 sub_cmd;
+	u32 size;
+	u32 wbuf[4];
+};
+
+/**
+ * intel_pmc_ipc() - PMC IPC Mailbox accessor
+ * @ipc_cmd:  struct pmc_ipc_cmd prepared with input to send
+ * @rbuf:     Allocated u32[4] array for returned IPC data
+ *
+ * Return: 0 on success. Non-zero on mailbox error
+ */
+int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, u32 *rbuf);
+
+#endif /* INTEL_PMC_IPC_H */
-- 
2.34.1