drivers/firmware/arm_scmi/msg.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * For transports using message passing.
   4  *
   5  * Derived from shm.c.
   6  *
   7  * Copyright (C) 2019-2024 ARM Ltd.
   8  * Copyright (C) 2020-2021 OpenSynergy GmbH
   9  */
  10
  11 #include <linux/types.h>
  12
  13 #include "common.h"
  14
  15 /*
  16  * struct scmi_msg_payld - Transport SDU layout
  17  *
  18  * The SCMI specification requires all parameters, message headers, return
  19  * arguments or any protocol data to be expressed in little endian format only.
  20  */
  21 struct scmi_msg_payld {
  22         __le32 msg_header;
  23         __le32 msg_payload[];
  24 };
  25
  26 /**
  27  * msg_command_size() - Actual size of transport SDU for command.
  28  *
  29  * @xfer: message which core has prepared for sending
  30  *
  31  * Return: transport SDU size.
  32  */
  33 static size_t msg_command_size(struct scmi_xfer *xfer)
  34 {
  35         return sizeof(struct scmi_msg_payld) + xfer->tx.len;
  36 }
  37
  38 /**
  39  * msg_response_size() - Maximum size of transport SDU for response.
  40  *
  41  * @xfer: message which core has prepared for sending
  42  *
  43  * Return: transport SDU size.
  44  */
  45 static size_t msg_response_size(struct scmi_xfer *xfer)
  46 {
  47         return sizeof(struct scmi_msg_payld) + sizeof(__le32) + xfer->rx.len;
  48 }
  49
  50 /**
  51  * msg_tx_prepare() - Set up transport SDU for command.
  52  *
  53  * @msg: transport SDU for command
  54  * @xfer: message which is being sent
  55  */
  56 static void msg_tx_prepare(struct scmi_msg_payld *msg, struct scmi_xfer *xfer)
  57 {
  58         msg->msg_header = cpu_to_le32(pack_scmi_header(&xfer->hdr));
  59         if (xfer->tx.buf)
  60                 memcpy(msg->msg_payload, xfer->tx.buf, xfer->tx.len);
  61 }
  62
  63 /**
  64  * msg_read_header() - Read SCMI header from transport SDU.
  65  *
  66  * @msg: transport SDU
  67  *
  68  * Return: SCMI header
  69  */
  70 static u32 msg_read_header(struct scmi_msg_payld *msg)
  71 {
  72         return le32_to_cpu(msg->msg_header);
  73 }
  74
  75 /**
  76  * msg_fetch_response() - Fetch response SCMI payload from transport SDU.
  77  *
  78  * @msg: transport SDU with response
  79  * @len: transport SDU size
  80  * @xfer: message being responded to
  81  */
  82 static void msg_fetch_response(struct scmi_msg_payld *msg,
  83                                size_t len, struct scmi_xfer *xfer)
  84 {
  85         size_t prefix_len = sizeof(*msg) + sizeof(msg->msg_payload[0]);
  86
  87         xfer->hdr.status = le32_to_cpu(msg->msg_payload[0]);
  88         xfer->rx.len = min_t(size_t, xfer->rx.len,
  89                              len >= prefix_len ? len - prefix_len : 0);
  90
  91         /* Take a copy to the rx buffer.. */
  92         memcpy(xfer->rx.buf, &msg->msg_payload[1], xfer->rx.len);
  93 }
  94
  95 /**
  96  * msg_fetch_notification() - Fetch notification payload from transport SDU.
  97  *
  98  * @msg: transport SDU with notification
  99  * @len: transport SDU size
 100  * @max_len: maximum SCMI payload size to fetch
 101  * @xfer: notification message
 102  */
 103 static void msg_fetch_notification(struct scmi_msg_payld *msg, size_t len,
 104                                    size_t max_len, struct scmi_xfer *xfer)
 105 {
 106         xfer->rx.len = min_t(size_t, max_len,
 107                              len >= sizeof(*msg) ? len - sizeof(*msg) : 0);
 108
 109         /* Take a copy to the rx buffer.. */
 110         memcpy(xfer->rx.buf, msg->msg_payload, xfer->rx.len);
 111 }
 112
 113 static const struct scmi_message_operations scmi_msg_ops = {
 114         .tx_prepare = msg_tx_prepare,
 115         .command_size = msg_command_size,
 116         .response_size = msg_response_size,
 117         .read_header = msg_read_header,
 118         .fetch_response = msg_fetch_response,
 119         .fetch_notification = msg_fetch_notification,
 120 };
 121
 122 const struct scmi_message_operations *scmi_message_operations_get(void)
 123 {
 124         return &scmi_msg_ops;
 125 }