1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Virtio I2C Bus Driver 4 * 5 * The Virtio I2C Specification: 6 * https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex 7 * 8 * Copyright (c) 2021 Intel Corporation. All rights reserved. 9 */ 10 11 #include <linux/acpi.h> 12 #include <linux/completion.h> 13 #include <linux/err.h> 14 #include <linux/i2c.h> 15 #include <linux/kernel.h> 16 #include <linux/module.h> 17 #include <linux/virtio.h> 18 #include <linux/virtio_ids.h> 19 #include <linux/virtio_config.h> 20 #include <linux/virtio_i2c.h> 21 22 /** 23 * struct virtio_i2c - virtio I2C data 24 * @vdev: virtio device for this controller 25 * @completion: completion of virtio I2C message 26 * @adap: I2C adapter for this controller 27 * @vq: the virtio virtqueue for communication 28 */ 29 struct virtio_i2c { 30 struct virtio_device *vdev; 31 struct completion completion; 32 struct i2c_adapter adap; 33 struct virtqueue *vq; 34 }; 35 36 /** 37 * struct virtio_i2c_req - the virtio I2C request structure 38 * @out_hdr: the OUT header of the virtio I2C message 39 * @buf: the buffer into which data is read, or from which it's written 40 * @in_hdr: the IN header of the virtio I2C message 41 */ 42 struct virtio_i2c_req { 43 struct virtio_i2c_out_hdr out_hdr ____cacheline_aligned; 44 uint8_t *buf ____cacheline_aligned; 45 struct virtio_i2c_in_hdr in_hdr ____cacheline_aligned; 46 }; 47 48 static void virtio_i2c_msg_done(struct virtqueue *vq) 49 { 50 struct virtio_i2c *vi = vq->vdev->priv; 51 52 complete(&vi->completion); 53 } 54 55 static int virtio_i2c_prepare_reqs(struct virtqueue *vq, 56 struct virtio_i2c_req *reqs, 57 struct i2c_msg *msgs, int num) 58 { 59 struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr; 60 int i; 61 62 for (i = 0; i < num; i++) { 63 int outcnt = 0, incnt = 0; 64 65 /* 66 * Only 7-bit mode supported for this moment. For the address 67 * format, Please check the Virtio I2C Specification. 68 */ 69 reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); 70 71 if (msgs[i].flags & I2C_M_RD) 72 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD); 73 74 if (i != num - 1) 75 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT); 76 77 sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr)); 78 sgs[outcnt++] = &out_hdr; 79 80 if (msgs[i].len) { 81 reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1); 82 if (!reqs[i].buf) 83 break; 84 85 sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len); 86 87 if (msgs[i].flags & I2C_M_RD) 88 sgs[outcnt + incnt++] = &msg_buf; 89 else 90 sgs[outcnt++] = &msg_buf; 91 } 92 93 sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); 94 sgs[outcnt + incnt++] = &in_hdr; 95 96 if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) { 97 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false); 98 break; 99 } 100 } 101 102 return i; 103 } 104 105 static int virtio_i2c_complete_reqs(struct virtqueue *vq, 106 struct virtio_i2c_req *reqs, 107 struct i2c_msg *msgs, int num, 108 bool timedout) 109 { 110 struct virtio_i2c_req *req; 111 bool failed = timedout; 112 unsigned int len; 113 int i, j = 0; 114 115 for (i = 0; i < num; i++) { 116 /* Detach the ith request from the vq */ 117 req = virtqueue_get_buf(vq, &len); 118 119 /* 120 * Condition req == &reqs[i] should always meet since we have 121 * total num requests in the vq. reqs[i] can never be NULL here. 122 */ 123 if (!failed && (WARN_ON(req != &reqs[i]) || 124 req->in_hdr.status != VIRTIO_I2C_MSG_OK)) 125 failed = true; 126 127 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed); 128 129 if (!failed) 130 j++; 131 } 132 133 return timedout ? -ETIMEDOUT : j; 134 } 135 136 static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, 137 int num) 138 { 139 struct virtio_i2c *vi = i2c_get_adapdata(adap); 140 struct virtqueue *vq = vi->vq; 141 struct virtio_i2c_req *reqs; 142 unsigned long time_left; 143 int count; 144 145 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); 146 if (!reqs) 147 return -ENOMEM; 148 149 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num); 150 if (!count) 151 goto err_free; 152 153 /* 154 * For the case where count < num, i.e. we weren't able to queue all the 155 * msgs, ideally we should abort right away and return early, but some 156 * of the messages are already sent to the remote I2C controller and the 157 * virtqueue will be left in undefined state in that case. We kick the 158 * remote here to clear the virtqueue, so we can try another set of 159 * messages later on. 160 */ 161 162 reinit_completion(&vi->completion); 163 virtqueue_kick(vq); 164 165 time_left = wait_for_completion_timeout(&vi->completion, adap->timeout); 166 if (!time_left) 167 dev_err(&adap->dev, "virtio i2c backend timeout.\n"); 168 169 count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left); 170 171 err_free: 172 kfree(reqs); 173 return count; 174 } 175 176 static void virtio_i2c_del_vqs(struct virtio_device *vdev) 177 { 178 vdev->config->reset(vdev); 179 vdev->config->del_vqs(vdev); 180 } 181 182 static int virtio_i2c_setup_vqs(struct virtio_i2c *vi) 183 { 184 struct virtio_device *vdev = vi->vdev; 185 186 vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg"); 187 return PTR_ERR_OR_ZERO(vi->vq); 188 } 189 190 static u32 virtio_i2c_func(struct i2c_adapter *adap) 191 { 192 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 193 } 194 195 static struct i2c_algorithm virtio_algorithm = { 196 .master_xfer = virtio_i2c_xfer, 197 .functionality = virtio_i2c_func, 198 }; 199 200 static int virtio_i2c_probe(struct virtio_device *vdev) 201 { 202 struct virtio_i2c *vi; 203 int ret; 204 205 if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) { 206 dev_err(&vdev->dev, "Zero-length request feature is mandatory\n"); 207 return -EINVAL; 208 } 209 210 vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL); 211 if (!vi) 212 return -ENOMEM; 213 214 vdev->priv = vi; 215 vi->vdev = vdev; 216 217 init_completion(&vi->completion); 218 219 ret = virtio_i2c_setup_vqs(vi); 220 if (ret) 221 return ret; 222 223 vi->adap.owner = THIS_MODULE; 224 snprintf(vi->adap.name, sizeof(vi->adap.name), 225 "i2c_virtio at virtio bus %d", vdev->index); 226 vi->adap.algo = &virtio_algorithm; 227 vi->adap.dev.parent = &vdev->dev; 228 vi->adap.dev.of_node = vdev->dev.of_node; 229 i2c_set_adapdata(&vi->adap, vi); 230 231 /* 232 * Setup ACPI node for controlled devices which will be probed through 233 * ACPI. 234 */ 235 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent)); 236 237 ret = i2c_add_adapter(&vi->adap); 238 if (ret) 239 virtio_i2c_del_vqs(vdev); 240 241 return ret; 242 } 243 244 static void virtio_i2c_remove(struct virtio_device *vdev) 245 { 246 struct virtio_i2c *vi = vdev->priv; 247 248 i2c_del_adapter(&vi->adap); 249 virtio_i2c_del_vqs(vdev); 250 } 251 252 static struct virtio_device_id id_table[] = { 253 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID }, 254 {} 255 }; 256 MODULE_DEVICE_TABLE(virtio, id_table); 257 258 #ifdef CONFIG_PM_SLEEP 259 static int virtio_i2c_freeze(struct virtio_device *vdev) 260 { 261 virtio_i2c_del_vqs(vdev); 262 return 0; 263 } 264 265 static int virtio_i2c_restore(struct virtio_device *vdev) 266 { 267 return virtio_i2c_setup_vqs(vdev->priv); 268 } 269 #endif 270 271 static const unsigned int features[] = { 272 VIRTIO_I2C_F_ZERO_LENGTH_REQUEST, 273 }; 274 275 static struct virtio_driver virtio_i2c_driver = { 276 .feature_table = features, 277 .feature_table_size = ARRAY_SIZE(features), 278 .id_table = id_table, 279 .probe = virtio_i2c_probe, 280 .remove = virtio_i2c_remove, 281 .driver = { 282 .name = "i2c_virtio", 283 }, 284 #ifdef CONFIG_PM_SLEEP 285 .freeze = virtio_i2c_freeze, 286 .restore = virtio_i2c_restore, 287 #endif 288 }; 289 module_virtio_driver(virtio_i2c_driver); 290 291 MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>"); 292 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>"); 293 MODULE_DESCRIPTION("Virtio i2c bus driver"); 294 MODULE_LICENSE("GPL"); 295