// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2025 Intel Corporation
 */

#include <linux/component.h>
#include <linux/mei_cl_bus.h>
#include <linux/module.h>
#include <linux/overflow.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/uuid.h>

#include <drm/intel/i915_component.h>
#include <drm/intel/intel_lb_mei_interface.h>

#include "mkhi.h"

/**
 * DOC: Late Binding Firmware Update/Upload
 *
 * Late Binding is a firmware update/upload mechanism that allows configuration
 * payloads to be securely delivered and applied at runtime, rather than
 * being embedded in the system firmware image (e.g., IFWI or SPI flash).
 *
 * This mechanism is used to update device-level configuration such as:
 * - Fan controller
 * - Voltage regulator (VR)
 *
 * Key Characteristics:
 * ---------------------
 * - Runtime Delivery:
 *   Firmware blobs are loaded by the host driver (e.g., Xe KMD)
 *   after the GPU or SoC has booted.
 *
 * - Secure and Authenticated:
 *   All payloads are signed and verified by the authentication firmware.
 *
 * - No Firmware Flashing Required:
 *   Updates are applied in volatile memory and do not require SPI flash
 *   modification or system reboot.
 *
 * - Re-entrant:
 *   Multiple updates of the same or different types can be applied
 *   sequentially within a single boot session.
 *
 * - Version Controlled:
 *   Each payload includes version and security version number (SVN)
 *   metadata to support anti-rollback enforcement.
 *
 * Upload Flow:
 * ------------
 * 1. Host driver (KMD or user-space tool) loads the late binding firmware.
 * 2. Firmware is passed to the MEI interface and forwarded to
 *    authentication firmware.
 * 3. Authentication firmware authenticates the payload and extracts
 *    command and data arrays.
 * 4. Authentication firmware delivers the configuration to PUnit/PCODE.
 * 5. Status is returned back to the host via MEI.
 */

#define INTEL_LB_CMD    0x12
#define INTEL_LB_RSP    (INTEL_LB_CMD | 0x80)

#define INTEL_LB_SEND_TIMEOUT_MSEC 3000
#define INTEL_LB_RECV_TIMEOUT_MSEC 3000

/**
 * struct mei_lb_req - Late Binding request structure
 * @header: MKHI message header (see struct mkhi_msg_hdr)
 * @type: Type of the Late Binding payload
 * @flags: Flags to be passed to the authentication firmware (e.g. %INTEL_LB_FLAGS_IS_PERSISTENT)
 * @reserved: Reserved for future use by authentication firmware, must be set to 0
 * @payload_size: Size of the payload data in bytes
 * @payload: Payload data to be sent to the authentication firmware
 */
struct mei_lb_req {
        struct mkhi_msg_hdr header;
        __le32 type;
        __le32 flags;
        __le32 reserved[2];
        __le32 payload_size;
        u8 payload[] __counted_by(payload_size);
} __packed;

/**
 * struct mei_lb_rsp - Late Binding response structure
 * @header: MKHI message header (see struct mkhi_msg_hdr)
 * @type: Type of the Late Binding payload
 * @reserved: Reserved for future use by authentication firmware, must be set to 0
 * @status: Status returned by authentication firmware (see &enum intel_lb_status)
 */
struct mei_lb_rsp {
        struct mkhi_msg_hdr header;
        __le32 type;
        __le32 reserved[2];
        __le32 status;
} __packed;

static bool mei_lb_check_response(const struct device *dev, ssize_t bytes,
                                  struct mei_lb_rsp *rsp)
{
        /*
         * Received message size may be smaller than the full message size when
         * reply contains only MKHI header with result field set to the error code.
         * Check the header size and content first to output exact error, if needed,
         * and then process to the whole message.
         */
        if (bytes < sizeof(rsp->header)) {
                dev_err(dev, "Received less than header size from the firmware: %zd < %zu\n",
                        bytes, sizeof(rsp->header));
                return false;
        }
        if (rsp->header.group_id != MKHI_GROUP_ID_GFX) {
                dev_err(dev, "Mismatch group id: 0x%x instead of 0x%x\n",
                        rsp->header.group_id, MKHI_GROUP_ID_GFX);
                return false;
        }
        if (rsp->header.command != INTEL_LB_RSP) {
                dev_err(dev, "Mismatch command: 0x%x instead of 0x%x\n",
                        rsp->header.command, INTEL_LB_RSP);
                return false;
        }
        if (rsp->header.result) {
                dev_err(dev, "Error in result: 0x%x\n", rsp->header.result);
                return false;
        }
        if (bytes < sizeof(*rsp)) {
                dev_err(dev, "Received less than message size from the firmware: %zd < %zu\n",
                        bytes, sizeof(*rsp));
                return false;
        }

        return true;
}

static int mei_lb_push_payload(struct device *dev, u32 type, u32 flags,
                               const void *payload, size_t payload_size)
{
        struct mei_cl_device *cldev;
        struct mei_lb_req *req = NULL;
        struct mei_lb_rsp rsp;
        size_t req_size;
        ssize_t bytes;
        int ret;

        cldev = to_mei_cl_device(dev);

        ret = mei_cldev_enable(cldev);
        if (ret) {
                dev_dbg(dev, "Failed to enable firmware client. %d\n", ret);
                return ret;
        }

        req_size = struct_size(req, payload, payload_size);
        if (req_size > mei_cldev_mtu(cldev)) {
                dev_err(dev, "Payload is too big: %zu\n", payload_size);
                ret = -EMSGSIZE;
                goto end;
        }

        req = kmalloc(req_size, GFP_KERNEL);
        if (!req) {
                ret = -ENOMEM;
                goto end;
        }

        req->header.group_id = MKHI_GROUP_ID_GFX;
        req->header.command = INTEL_LB_CMD;
        req->type = cpu_to_le32(type);
        req->flags = cpu_to_le32(flags);
        req->reserved[0] = 0;
        req->reserved[1] = 0;
        req->payload_size = cpu_to_le32(payload_size);
        memcpy(req->payload, payload, payload_size);

        bytes = mei_cldev_send_timeout(cldev, (u8 *)req, req_size,
                                       INTEL_LB_SEND_TIMEOUT_MSEC);
        if (bytes < 0) {
                dev_err(dev, "Failed to send late binding request to firmware. %zd\n", bytes);
                ret = bytes;
                goto end;
        }

        bytes = mei_cldev_recv_timeout(cldev, (u8 *)&rsp, sizeof(rsp),
                                       INTEL_LB_RECV_TIMEOUT_MSEC);
        if (bytes < 0) {
                dev_err(dev, "Failed to receive late binding reply from MEI firmware. %zd\n",
                        bytes);
                ret = bytes;
                goto end;
        }
        if (!mei_lb_check_response(dev, bytes, &rsp)) {
                dev_err(dev, "Bad response from the firmware. header: %02x %02x %02x %02x\n",
                        rsp.header.group_id, rsp.header.command,
                        rsp.header.reserved, rsp.header.result);
                ret = -EPROTO;
                goto end;
        }

        dev_dbg(dev, "status = %u\n", le32_to_cpu(rsp.status));
        ret = (int)le32_to_cpu(rsp.status);
end:
        mei_cldev_disable(cldev);
        kfree(req);
        return ret;
}

static const struct intel_lb_component_ops mei_lb_ops = {
        .push_payload = mei_lb_push_payload,
};

static int mei_lb_component_master_bind(struct device *dev)
{
        return component_bind_all(dev, (void *)&mei_lb_ops);
}

static void mei_lb_component_master_unbind(struct device *dev)
{
        component_unbind_all(dev, (void *)&mei_lb_ops);
}

static const struct component_master_ops mei_lb_component_master_ops = {
        .bind = mei_lb_component_master_bind,
        .unbind = mei_lb_component_master_unbind,
};

static int mei_lb_component_match(struct device *dev, int subcomponent,
                                  void *data)
{
        /*
         * This function checks if requester is Intel %PCI_CLASS_DISPLAY_VGA or
         * %PCI_CLASS_DISPLAY_OTHER device, and checks if the requester is the
         * grand parent of mei_if i.e. late bind MEI device
         */
        struct device *base = data;
        struct pci_dev *pdev;

        if (!dev)
                return 0;

        if (!dev_is_pci(dev))
                return 0;

        pdev = to_pci_dev(dev);

        if (pdev->vendor != PCI_VENDOR_ID_INTEL)
                return 0;

        if (pdev->class != (PCI_CLASS_DISPLAY_VGA << 8) &&
            pdev->class != (PCI_CLASS_DISPLAY_OTHER << 8))
                return 0;

        if (subcomponent != INTEL_COMPONENT_LB)
                return 0;

        base = base->parent;
        if (!base) /* mei device */
                return 0;

        base = base->parent; /* pci device */

        return !!base && dev == base;
}

static int mei_lb_probe(struct mei_cl_device *cldev,
                        const struct mei_cl_device_id *id)
{
        struct component_match *master_match = NULL;
        int ret;

        component_match_add_typed(&cldev->dev, &master_match,
                                  mei_lb_component_match, &cldev->dev);
        if (IS_ERR_OR_NULL(master_match))
                return -ENOMEM;

        ret = component_master_add_with_match(&cldev->dev,
                                              &mei_lb_component_master_ops,
                                              master_match);
        if (ret < 0)
                dev_err(&cldev->dev, "Failed to add late binding master component. %d\n", ret);

        return ret;
}

static void mei_lb_remove(struct mei_cl_device *cldev)
{
        component_master_del(&cldev->dev, &mei_lb_component_master_ops);
}

#define MEI_GUID_MKHI UUID_LE(0xe2c2afa2, 0x3817, 0x4d19, \
                              0x9d, 0x95, 0x6, 0xb1, 0x6b, 0x58, 0x8a, 0x5d)

static const struct mei_cl_device_id mei_lb_tbl[] = {
        { .uuid = MEI_GUID_MKHI, .version = MEI_CL_VERSION_ANY },
        { }
};
MODULE_DEVICE_TABLE(mei, mei_lb_tbl);

static struct mei_cl_driver mei_lb_driver = {
        .id_table = mei_lb_tbl,
        .name = "mei_lb",
        .probe = mei_lb_probe,
        .remove = mei_lb_remove,
};

module_mei_cl_driver(mei_lb_driver);

MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("MEI Late Binding Firmware Update/Upload");