drivers/firmware/arm_scmi/smc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * System Control and Management Interface (SCMI) Message SMC/HVC
   4  * Transport driver
   5  *
   6  * Copyright 2020 NXP
   7  */
   8
   9 #include <linux/arm-smccc.h>
  10 #include <linux/atomic.h>
  11 #include <linux/device.h>
  12 #include <linux/err.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/mutex.h>
  15 #include <linux/of.h>
  16 #include <linux/of_address.h>
  17 #include <linux/of_irq.h>
  18 #include <linux/processor.h>
  19 #include <linux/slab.h>
  20
  21 #include "common.h"
  22
  23 /*
  24  * The shmem address is split into 4K page and offset.
  25  * This is to make sure the parameters fit in 32bit arguments of the
  26  * smc/hvc call to keep it uniform across smc32/smc64 conventions.
  27  * This however limits the shmem address to 44 bit.
  28  *
  29  * These optional parameters can be used to distinguish among multiple
  30  * scmi instances that are using the same smc-id.
  31  * The page parameter is passed in r1/x1/w1 register and the offset parameter
  32  * is passed in r2/x2/w2 register.
  33  */
  34
  35 #define SHMEM_SIZE (SZ_4K)
  36 #define SHMEM_SHIFT 12
  37 #define SHMEM_PAGE(x) (_UL((x) >> SHMEM_SHIFT))
  38 #define SHMEM_OFFSET(x) ((x) & (SHMEM_SIZE - 1))
  39
  40 /**
  41  * struct scmi_smc - Structure representing a SCMI smc transport
  42  *
  43  * @irq: An optional IRQ for completion
  44  * @cinfo: SCMI channel info
  45  * @shmem: Transmit/Receive shared memory area
  46  * @shmem_lock: Lock to protect access to Tx/Rx shared memory area.
  47  *              Used when NOT operating in atomic mode.
  48  * @inflight: Atomic flag to protect access to Tx/Rx shared memory area.
  49  *            Used when operating in atomic mode.
  50  * @func_id: smc/hvc call function id
  51  * @param_page: 4K page number of the shmem channel
  52  * @param_offset: Offset within the 4K page of the shmem channel
  53  */
  54
  55 struct scmi_smc {
  56         int irq;
  57         struct scmi_chan_info *cinfo;
  58         struct scmi_shared_mem __iomem *shmem;
  59         /* Protect access to shmem area */
  60         struct mutex shmem_lock;
  61 #define INFLIGHT_NONE   MSG_TOKEN_MAX
  62         atomic_t inflight;
  63         u32 func_id;
  64         u32 param_page;
  65         u32 param_offset;
  66 };
  67
  68 static irqreturn_t smc_msg_done_isr(int irq, void *data)
  69 {
  70         struct scmi_smc *scmi_info = data;
  71
  72         scmi_rx_callback(scmi_info->cinfo,
  73                          shmem_read_header(scmi_info->shmem), NULL);
  74
  75         return IRQ_HANDLED;
  76 }
  77
  78 static bool smc_chan_available(struct device_node *of_node, int idx)
  79 {
  80         struct device_node *np = of_parse_phandle(of_node, "shmem", 0);
  81         if (!np)
  82                 return false;
  83
  84         of_node_put(np);
  85         return true;
  86 }
  87
  88 static inline void smc_channel_lock_init(struct scmi_smc *scmi_info)
  89 {
  90         if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
  91                 atomic_set(&scmi_info->inflight, INFLIGHT_NONE);
  92         else
  93                 mutex_init(&scmi_info->shmem_lock);
  94 }
  95
  96 static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight)
  97 {
  98         int ret;
  99
 100         ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq);
 101
 102         return ret == INFLIGHT_NONE;
 103 }
 104
 105 static inline void
 106 smc_channel_lock_acquire(struct scmi_smc *scmi_info,
 107                          struct scmi_xfer *xfer __maybe_unused)
 108 {
 109         if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
 110                 spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight));
 111         else
 112                 mutex_lock(&scmi_info->shmem_lock);
 113 }
 114
 115 static inline void smc_channel_lock_release(struct scmi_smc *scmi_info)
 116 {
 117         if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
 118                 atomic_set(&scmi_info->inflight, INFLIGHT_NONE);
 119         else
 120                 mutex_unlock(&scmi_info->shmem_lock);
 121 }
 122
 123 static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 124                           bool tx)
 125 {
 126         struct device *cdev = cinfo->dev;
 127         struct scmi_smc *scmi_info;
 128         resource_size_t size;
 129         struct resource res;
 130         struct device_node *np;
 131         u32 func_id;
 132         int ret;
 133
 134         if (!tx)
 135                 return -ENODEV;
 136
 137         scmi_info = devm_kzalloc(dev, sizeof(*scmi_info), GFP_KERNEL);
 138         if (!scmi_info)
 139                 return -ENOMEM;
 140
 141         np = of_parse_phandle(cdev->of_node, "shmem", 0);
 142         if (!of_device_is_compatible(np, "arm,scmi-shmem")) {
 143                 of_node_put(np);
 144                 return -ENXIO;
 145         }
 146
 147         ret = of_address_to_resource(np, 0, &res);
 148         of_node_put(np);
 149         if (ret) {
 150                 dev_err(cdev, "failed to get SCMI Tx shared memory\n");
 151                 return ret;
 152         }
 153
 154         size = resource_size(&res);
 155         scmi_info->shmem = devm_ioremap(dev, res.start, size);
 156         if (!scmi_info->shmem) {
 157                 dev_err(dev, "failed to ioremap SCMI Tx shared memory\n");
 158                 return -EADDRNOTAVAIL;
 159         }
 160
 161         ret = of_property_read_u32(dev->of_node, "arm,smc-id", &func_id);
 162         if (ret < 0)
 163                 return ret;
 164
 165         if (of_device_is_compatible(dev->of_node, "arm,scmi-smc-param")) {
 166                 scmi_info->param_page = SHMEM_PAGE(res.start);
 167                 scmi_info->param_offset = SHMEM_OFFSET(res.start);
 168         }
 169         /*
 170          * If there is an interrupt named "a2p", then the service and
 171          * completion of a message is signaled by an interrupt rather than by
 172          * the return of the SMC call.
 173          */
 174         scmi_info->irq = of_irq_get_byname(cdev->of_node, "a2p");
 175         if (scmi_info->irq > 0) {
 176                 ret = request_irq(scmi_info->irq, smc_msg_done_isr,
 177                                   IRQF_NO_SUSPEND, dev_name(dev), scmi_info);
 178                 if (ret) {
 179                         dev_err(dev, "failed to setup SCMI smc irq\n");
 180                         return ret;
 181                 }
 182         } else {
 183                 cinfo->no_completion_irq = true;
 184         }
 185
 186         scmi_info->func_id = func_id;
 187         scmi_info->cinfo = cinfo;
 188         smc_channel_lock_init(scmi_info);
 189         cinfo->transport_info = scmi_info;
 190
 191         return 0;
 192 }
 193
 194 static int smc_chan_free(int id, void *p, void *data)
 195 {
 196         struct scmi_chan_info *cinfo = p;
 197         struct scmi_smc *scmi_info = cinfo->transport_info;
 198
 199         /* Ignore any possible further reception on the IRQ path */
 200         if (scmi_info->irq > 0)
 201                 free_irq(scmi_info->irq, scmi_info);
 202
 203         cinfo->transport_info = NULL;
 204         scmi_info->cinfo = NULL;
 205
 206         return 0;
 207 }
 208
 209 static int smc_send_message(struct scmi_chan_info *cinfo,
 210                             struct scmi_xfer *xfer)
 211 {
 212         struct scmi_smc *scmi_info = cinfo->transport_info;
 213         struct arm_smccc_res res;
 214         unsigned long page = scmi_info->param_page;
 215         unsigned long offset = scmi_info->param_offset;
 216
 217         /*
 218          * Channel will be released only once response has been
 219          * surely fully retrieved, so after .mark_txdone()
 220          */
 221         smc_channel_lock_acquire(scmi_info, xfer);
 222
 223         shmem_tx_prepare(scmi_info->shmem, xfer, cinfo);
 224
 225         arm_smccc_1_1_invoke(scmi_info->func_id, page, offset, 0, 0, 0, 0, 0,
 226                              &res);
 227
 228         /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
 229         if (res.a0) {
 230                 smc_channel_lock_release(scmi_info);
 231                 return -EOPNOTSUPP;
 232         }
 233
 234         return 0;
 235 }
 236
 237 static void smc_fetch_response(struct scmi_chan_info *cinfo,
 238                                struct scmi_xfer *xfer)
 239 {
 240         struct scmi_smc *scmi_info = cinfo->transport_info;
 241
 242         shmem_fetch_response(scmi_info->shmem, xfer);
 243 }
 244
 245 static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret,
 246                             struct scmi_xfer *__unused)
 247 {
 248         struct scmi_smc *scmi_info = cinfo->transport_info;
 249
 250         smc_channel_lock_release(scmi_info);
 251 }
 252
 253 static const struct scmi_transport_ops scmi_smc_ops = {
 254         .chan_available = smc_chan_available,
 255         .chan_setup = smc_chan_setup,
 256         .chan_free = smc_chan_free,
 257         .send_message = smc_send_message,
 258         .mark_txdone = smc_mark_txdone,
 259         .fetch_response = smc_fetch_response,
 260 };
 261
 262 const struct scmi_desc scmi_smc_desc = {
 263         .ops = &scmi_smc_ops,
 264         .max_rx_timeout_ms = 30,
 265         .max_msg = 20,
 266         .max_msg_size = 128,
 267         /*
 268          * Setting .sync_cmds_atomic_replies to true for SMC assumes that,
 269          * once the SMC instruction has completed successfully, the issued
 270          * SCMI command would have been already fully processed by the SCMI
 271          * platform firmware and so any possible response value expected
 272          * for the issued command will be immmediately ready to be fetched
 273          * from the shared memory area.
 274          */
 275         .sync_cmds_completed_on_ret = true,
 276         .atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE),
 277 };