[PATCH net-next v2 1/5] platform/x86: intel_pmc_core: Add IPC mailbox accessor function and add SoC register access

[Choong Yong Liang]

From: "David E. Box" <david.e.box@xxxxxxxxxxxxxxx>

- Exports intel_pmc_core_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@xxxxxxxxxxxxxxx>
Signed-off-by: Chao Qin <chao.qin@xxxxxxxxx>
Signed-off-by: Choong Yong Liang <yong.liang.choong@xxxxxxxxxxxxxxx>
---
 MAINTAINERS                                   |  1 +
 drivers/platform/x86/intel/pmc/core.c         | 60 +++++++++++++++++++
 .../linux/platform_data/x86/intel_pmc_core.h  | 41 +++++++++++++
 3 files changed, 102 insertions(+)
 create mode 100644 include/linux/platform_data/x86/intel_pmc_core.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 069e176d607a..8a034dee9da9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10648,6 +10648,7 @@ L:	platform-driver-x86@xxxxxxxxxxxxxxx
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-platform-intel-pmc
 F:	drivers/platform/x86/intel/pmc/
+F:	linux/platform_data/x86/intel_pmc_core.h
 
 INTEL PMIC GPIO DRIVERS
 M:	Andy Shevchenko <andy@xxxxxxxxxx>
diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
index 5a36b3f77bc5..6fb1b0f453d8 100644
--- a/drivers/platform/x86/intel/pmc/core.c
+++ b/drivers/platform/x86/intel/pmc/core.c
@@ -20,6 +20,7 @@
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/suspend.h>
+#include <linux/platform_data/x86/intel_pmc_core.h>
 
 #include <asm/cpu_device_id.h>
 #include <asm/intel-family.h>
@@ -28,6 +29,8 @@
 
 #include "core.h"
 
+#define PMC_IPCS_PARAM_COUNT           7
+
 /* Maximum number of modes supported by platfoms that has low power mode capability */
 const char *pmc_lpm_modes[] = {
 	"S0i2.0",
@@ -53,6 +56,63 @@ const struct pmc_bit_map msr_map[] = {
 	{}
 };
 
+int intel_pmc_core_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_core_ipc);
+
 static inline u32 pmc_core_reg_read(struct pmc *pmc, int reg_offset)
 {
 	return readl(pmc->regbase + reg_offset);
diff --git a/include/linux/platform_data/x86/intel_pmc_core.h b/include/linux/platform_data/x86/intel_pmc_core.h
new file mode 100644
index 000000000000..9bb3394fedcf
--- /dev/null
+++ b/include/linux/platform_data/x86/intel_pmc_core.h
@@ -0,0 +1,41 @@
+/* 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@xxxxxxxxxxxxxxx>
+ *          David E. Box <david.e.box@xxxxxxxxxxxxxxx>
+ */
+#ifndef INTEL_PMC_CORE_H
+#define INTEL_PMC_CORE_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];
+};
+
+#if IS_ENABLED(CONFIG_INTEL_PMC_CORE)
+/**
+ * intel_pmc_core_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_core_ipc(struct pmc_ipc_cmd *ipc_cmd, u32 *rbuf);
+#else
+static inline int intel_pmc_core_ipc(struct pmc_ipc_cmd *ipc_cmd, u32 *rbuf)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_INTEL_PMC_CORE */
+
+#endif /* INTEL_PMC_CORE_H */
-- 
2.25.1