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 { 109 struct virtio_i2c_req *req; 110 bool failed = false; 111 unsigned int len; 112 int i, j = 0; 113 114 for (i = 0; i < num; i++) { 115 /* Detach the ith request from the vq */ 116 req = virtqueue_get_buf(vq, &len); 117 118 /* 119 * Condition req == &reqs[i] should always meet since we have 120 * total num requests in the vq. reqs[i] can never be NULL here. 121 */ 122 if (!failed && (WARN_ON(req != &reqs[i]) || 123 req->in_hdr.status != VIRTIO_I2C_MSG_OK)) 124 failed = true; 125 126 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed); 127 128 if (!failed) 129 j++; 130 } 131 132 return j; 133 } 134 135 static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, 136 int num) 137 { 138 struct virtio_i2c *vi = i2c_get_adapdata(adap); 139 struct virtqueue *vq = vi->vq; 140 struct virtio_i2c_req *reqs; 141 int count; 142 143 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); 144 if (!reqs) 145 return -ENOMEM; 146 147 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num); 148 if (!count) 149 goto err_free; 150 151 /* 152 * For the case where count < num, i.e. we weren't able to queue all the 153 * msgs, ideally we should abort right away and return early, but some 154 * of the messages are already sent to the remote I2C controller and the 155 * virtqueue will be left in undefined state in that case. We kick the 156 * remote here to clear the virtqueue, so we can try another set of 157 * messages later on. 158 */ 159 160 reinit_completion(&vi->completion); 161 virtqueue_kick(vq); 162 163 wait_for_completion(&vi->completion); 164 165 count = virtio_i2c_complete_reqs(vq, reqs, msgs, count); 166 167 err_free: 168 kfree(reqs); 169 return count; 170 } 171 172 static void virtio_i2c_del_vqs(struct virtio_device *vdev) 173 { 174 vdev->config->reset(vdev); 175 vdev->config->del_vqs(vdev); 176 } 177 178 static int virtio_i2c_setup_vqs(struct virtio_i2c *vi) 179 { 180 struct virtio_device *vdev = vi->vdev; 181 182 vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg"); 183 return PTR_ERR_OR_ZERO(vi->vq); 184 } 185 186 static u32 virtio_i2c_func(struct i2c_adapter *adap) 187 { 188 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 189 } 190 191 static struct i2c_algorithm virtio_algorithm = { 192 .master_xfer = virtio_i2c_xfer, 193 .functionality = virtio_i2c_func, 194 }; 195 196 static int virtio_i2c_probe(struct virtio_device *vdev) 197 { 198 struct virtio_i2c *vi; 199 int ret; 200 201 if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) { 202 dev_err(&vdev->dev, "Zero-length request feature is mandatory\n"); 203 return -EINVAL; 204 } 205 206 vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL); 207 if (!vi) 208 return -ENOMEM; 209 210 vdev->priv = vi; 211 vi->vdev = vdev; 212 213 init_completion(&vi->completion); 214 215 ret = virtio_i2c_setup_vqs(vi); 216 if (ret) 217 return ret; 218 219 vi->adap.owner = THIS_MODULE; 220 snprintf(vi->adap.name, sizeof(vi->adap.name), 221 "i2c_virtio at virtio bus %d", vdev->index); 222 vi->adap.algo = &virtio_algorithm; 223 vi->adap.dev.parent = &vdev->dev; 224 vi->adap.dev.of_node = vdev->dev.of_node; 225 i2c_set_adapdata(&vi->adap, vi); 226 227 /* 228 * Setup ACPI node for controlled devices which will be probed through 229 * ACPI. 230 */ 231 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent)); 232 233 ret = i2c_add_adapter(&vi->adap); 234 if (ret) 235 virtio_i2c_del_vqs(vdev); 236 237 return ret; 238 } 239 240 static void virtio_i2c_remove(struct virtio_device *vdev) 241 { 242 struct virtio_i2c *vi = vdev->priv; 243 244 i2c_del_adapter(&vi->adap); 245 virtio_i2c_del_vqs(vdev); 246 } 247 248 static struct virtio_device_id id_table[] = { 249 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID }, 250 {} 251 }; 252 MODULE_DEVICE_TABLE(virtio, id_table); 253 254 #ifdef CONFIG_PM_SLEEP 255 static int virtio_i2c_freeze(struct virtio_device *vdev) 256 { 257 virtio_i2c_del_vqs(vdev); 258 return 0; 259 } 260 261 static int virtio_i2c_restore(struct virtio_device *vdev) 262 { 263 return virtio_i2c_setup_vqs(vdev->priv); 264 } 265 #endif 266 267 static const unsigned int features[] = { 268 VIRTIO_I2C_F_ZERO_LENGTH_REQUEST, 269 }; 270 271 static struct virtio_driver virtio_i2c_driver = { 272 .feature_table = features, 273 .feature_table_size = ARRAY_SIZE(features), 274 .id_table = id_table, 275 .probe = virtio_i2c_probe, 276 .remove = virtio_i2c_remove, 277 .driver = { 278 .name = "i2c_virtio", 279 }, 280 #ifdef CONFIG_PM_SLEEP 281 .freeze = virtio_i2c_freeze, 282 .restore = virtio_i2c_restore, 283 #endif 284 }; 285 module_virtio_driver(virtio_i2c_driver); 286 287 MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>"); 288 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>"); 289 MODULE_DESCRIPTION("Virtio i2c bus driver"); 290 MODULE_LICENSE("GPL"); 291