drivers/firmware/arm_scmi/mailbox.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * System Control and Management Interface (SCMI) Message Mailbox Transport
   4  * driver.
   5  *
   6  * Copyright (C) 2019 ARM Ltd.
   7  */
   8
   9 #include <linux/err.h>
  10 #include <linux/device.h>
  11 #include <linux/mailbox_client.h>
  12 #include <linux/of.h>
  13 #include <linux/of_address.h>
  14 #include <linux/slab.h>
  15
  16 #include "common.h"
  17
  18 /**
  19  * struct scmi_mailbox - Structure representing a SCMI mailbox transport
  20  *
  21  * @cl: Mailbox Client
  22  * @chan: Transmit/Receive mailbox channel
  23  * @cinfo: SCMI channel info
  24  * @shmem: Transmit/Receive shared memory area
  25  */
  26 struct scmi_mailbox {
  27         struct mbox_client cl;
  28         struct mbox_chan *chan;
  29         struct scmi_chan_info *cinfo;
  30         struct scmi_shared_mem __iomem *shmem;
  31 };
  32
  33 #define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
  34
  35 static void tx_prepare(struct mbox_client *cl, void *m)
  36 {
  37         struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
  38
  39         shmem_tx_prepare(smbox->shmem, m);
  40 }
  41
  42 static void rx_callback(struct mbox_client *cl, void *m)
  43 {
  44         struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
  45
  46         scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem));
  47 }
  48
  49 static bool mailbox_chan_available(struct device *dev, int idx)
  50 {
  51         return !of_parse_phandle_with_args(dev->of_node, "mboxes",
  52                                            "#mbox-cells", idx, NULL);
  53 }
  54
  55 static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
  56                               bool tx)
  57 {
  58         const char *desc = tx ? "Tx" : "Rx";
  59         struct device *cdev = cinfo->dev;
  60         struct scmi_mailbox *smbox;
  61         struct device_node *shmem;
  62         int ret, idx = tx ? 0 : 1;
  63         struct mbox_client *cl;
  64         resource_size_t size;
  65         struct resource res;
  66
  67         smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
  68         if (!smbox)
  69                 return -ENOMEM;
  70
  71         shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
  72         ret = of_address_to_resource(shmem, 0, &res);
  73         of_node_put(shmem);
  74         if (ret) {
  75                 dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
  76                 return ret;
  77         }
  78
  79         size = resource_size(&res);
  80         smbox->shmem = devm_ioremap(dev, res.start, size);
  81         if (!smbox->shmem) {
  82                 dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
  83                 return -EADDRNOTAVAIL;
  84         }
  85
  86         cl = &smbox->cl;
  87         cl->dev = cdev;
  88         cl->tx_prepare = tx ? tx_prepare : NULL;
  89         cl->rx_callback = rx_callback;
  90         cl->tx_block = false;
  91         cl->knows_txdone = tx;
  92
  93         smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
  94         if (IS_ERR(smbox->chan)) {
  95                 ret = PTR_ERR(smbox->chan);
  96                 if (ret != -EPROBE_DEFER)
  97                         dev_err(cdev, "failed to request SCMI %s mailbox\n",
  98                                 tx ? "Tx" : "Rx");
  99                 return ret;
 100         }
 101
 102         cinfo->transport_info = smbox;
 103         smbox->cinfo = cinfo;
 104
 105         return 0;
 106 }
 107
 108 static int mailbox_chan_free(int id, void *p, void *data)
 109 {
 110         struct scmi_chan_info *cinfo = p;
 111         struct scmi_mailbox *smbox = cinfo->transport_info;
 112
 113         if (smbox && !IS_ERR(smbox->chan)) {
 114                 mbox_free_channel(smbox->chan);
 115                 cinfo->transport_info = NULL;
 116                 smbox->chan = NULL;
 117                 smbox->cinfo = NULL;
 118         }
 119
 120         scmi_free_channel(cinfo, data, id);
 121
 122         return 0;
 123 }
 124
 125 static int mailbox_send_message(struct scmi_chan_info *cinfo,
 126                                 struct scmi_xfer *xfer)
 127 {
 128         struct scmi_mailbox *smbox = cinfo->transport_info;
 129         int ret;
 130
 131         ret = mbox_send_message(smbox->chan, xfer);
 132
 133         /* mbox_send_message returns non-negative value on success, so reset */
 134         if (ret > 0)
 135                 ret = 0;
 136
 137         return ret;
 138 }
 139
 140 static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret)
 141 {
 142         struct scmi_mailbox *smbox = cinfo->transport_info;
 143
 144         /*
 145          * NOTE: we might prefer not to need the mailbox ticker to manage the
 146          * transfer queueing since the protocol layer queues things by itself.
 147          * Unfortunately, we have to kick the mailbox framework after we have
 148          * received our message.
 149          */
 150         mbox_client_txdone(smbox->chan, ret);
 151 }
 152
 153 static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
 154                                    struct scmi_xfer *xfer)
 155 {
 156         struct scmi_mailbox *smbox = cinfo->transport_info;
 157
 158         shmem_fetch_response(smbox->shmem, xfer);
 159 }
 160
 161 static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
 162                                        size_t max_len, struct scmi_xfer *xfer)
 163 {
 164         struct scmi_mailbox *smbox = cinfo->transport_info;
 165
 166         shmem_fetch_notification(smbox->shmem, max_len, xfer);
 167 }
 168
 169 static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
 170 {
 171         struct scmi_mailbox *smbox = cinfo->transport_info;
 172
 173         shmem_clear_channel(smbox->shmem);
 174 }
 175
 176 static bool
 177 mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
 178 {
 179         struct scmi_mailbox *smbox = cinfo->transport_info;
 180
 181         return shmem_poll_done(smbox->shmem, xfer);
 182 }
 183
 184 static const struct scmi_transport_ops scmi_mailbox_ops = {
 185         .chan_available = mailbox_chan_available,
 186         .chan_setup = mailbox_chan_setup,
 187         .chan_free = mailbox_chan_free,
 188         .send_message = mailbox_send_message,
 189         .mark_txdone = mailbox_mark_txdone,
 190         .fetch_response = mailbox_fetch_response,
 191         .fetch_notification = mailbox_fetch_notification,
 192         .clear_channel = mailbox_clear_channel,
 193         .poll_done = mailbox_poll_done,
 194 };
 195
 196 const struct scmi_desc scmi_mailbox_desc = {
 197         .ops = &scmi_mailbox_ops,
 198         .max_rx_timeout_ms = 30, /* We may increase this if required */
 199         .max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
 200         .max_msg_size = 128,
 201 };