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

Choong Yong Liang
2025-02-06T13:20:37Z

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