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 * @adap: I2C adapter for this controller 26 * @vq: the virtio virtqueue for communication 27 */ 28 struct virtio_i2c { 29 struct virtio_device *vdev; 30 struct i2c_adapter adap; 31 struct virtqueue *vq; 32 }; 33 34 /** 35 * struct virtio_i2c_req - the virtio I2C request structure 36 * @completion: completion of virtio I2C message 37 * @out_hdr: the OUT header of the virtio I2C message 38 * @buf: the buffer into which data is read, or from which it's written 39 * @in_hdr: the IN header of the virtio I2C message 40 */ 41 struct virtio_i2c_req { 42 struct completion completion; 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_req *req; 51 unsigned int len; 52 53 while ((req = virtqueue_get_buf(vq, &len))) 54 complete(&req->completion); 55 } 56 57 static int virtio_i2c_prepare_reqs(struct virtqueue *vq, 58 struct virtio_i2c_req *reqs, 59 struct i2c_msg *msgs, int num) 60 { 61 struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr; 62 int i; 63 64 for (i = 0; i < num; i++) { 65 int outcnt = 0, incnt = 0; 66 67 init_completion(&reqs[i].completion); 68 69 /* 70 * Only 7-bit mode supported for this moment. For the address 71 * format, Please check the Virtio I2C Specification. 72 */ 73 reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); 74 75 if (msgs[i].flags & I2C_M_RD) 76 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD); 77 78 if (i != num - 1) 79 reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT); 80 81 sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr)); 82 sgs[outcnt++] = &out_hdr; 83 84 if (msgs[i].len) { 85 reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1); 86 if (!reqs[i].buf) 87 break; 88 89 sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len); 90 91 if (msgs[i].flags & I2C_M_RD) 92 sgs[outcnt + incnt++] = &msg_buf; 93 else 94 sgs[outcnt++] = &msg_buf; 95 } 96 97 sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); 98 sgs[outcnt + incnt++] = &in_hdr; 99 100 if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) { 101 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false); 102 break; 103 } 104 } 105 106 return i; 107 } 108 109 static int virtio_i2c_complete_reqs(struct virtqueue *vq, 110 struct virtio_i2c_req *reqs, 111 struct i2c_msg *msgs, int num) 112 { 113 bool failed = false; 114 int i, j = 0; 115 116 for (i = 0; i < num; i++) { 117 struct virtio_i2c_req *req = &reqs[i]; 118 119 wait_for_completion(&req->completion); 120 121 if (!failed && req->in_hdr.status != VIRTIO_I2C_MSG_OK) 122 failed = true; 123 124 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed); 125 126 if (!failed) 127 j++; 128 } 129 130 return j; 131 } 132 133 static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, 134 int num) 135 { 136 struct virtio_i2c *vi = i2c_get_adapdata(adap); 137 struct virtqueue *vq = vi->vq; 138 struct virtio_i2c_req *reqs; 139 int count; 140 141 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); 142 if (!reqs) 143 return -ENOMEM; 144 145 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num); 146 if (!count) 147 goto err_free; 148 149 /* 150 * For the case where count < num, i.e. we weren't able to queue all the 151 * msgs, ideally we should abort right away and return early, but some 152 * of the messages are already sent to the remote I2C controller and the 153 * virtqueue will be left in undefined state in that case. We kick the 154 * remote here to clear the virtqueue, so we can try another set of 155 * messages later on. 156 */ 157 virtqueue_kick(vq); 158 159 count = virtio_i2c_complete_reqs(vq, reqs, msgs, count); 160 161 err_free: 162 kfree(reqs); 163 return count; 164 } 165 166 static void virtio_i2c_del_vqs(struct virtio_device *vdev) 167 { 168 virtio_reset_device(vdev); 169 vdev->config->del_vqs(vdev); 170 } 171 172 static int virtio_i2c_setup_vqs(struct virtio_i2c *vi) 173 { 174 struct virtio_device *vdev = vi->vdev; 175 176 vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg"); 177 return PTR_ERR_OR_ZERO(vi->vq); 178 } 179 180 static u32 virtio_i2c_func(struct i2c_adapter *adap) 181 { 182 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 183 } 184 185 static const struct i2c_algorithm virtio_algorithm = { 186 .xfer = virtio_i2c_xfer, 187 .functionality = virtio_i2c_func, 188 }; 189 190 static int virtio_i2c_probe(struct virtio_device *vdev) 191 { 192 struct virtio_i2c *vi; 193 int ret; 194 195 if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) { 196 dev_err(&vdev->dev, "Zero-length request feature is mandatory\n"); 197 return -EINVAL; 198 } 199 200 vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL); 201 if (!vi) 202 return -ENOMEM; 203 204 vdev->priv = vi; 205 vi->vdev = vdev; 206 207 ret = virtio_i2c_setup_vqs(vi); 208 if (ret) 209 return ret; 210 211 vi->adap.owner = THIS_MODULE; 212 snprintf(vi->adap.name, sizeof(vi->adap.name), 213 "i2c_virtio at virtio bus %d", vdev->index); 214 vi->adap.algo = &virtio_algorithm; 215 vi->adap.dev.parent = &vdev->dev; 216 vi->adap.dev.of_node = vdev->dev.of_node; 217 i2c_set_adapdata(&vi->adap, vi); 218 219 /* 220 * Setup ACPI node for controlled devices which will be probed through 221 * ACPI. 222 */ 223 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent)); 224 225 ret = i2c_add_adapter(&vi->adap); 226 if (ret) 227 virtio_i2c_del_vqs(vdev); 228 229 return ret; 230 } 231 232 static void virtio_i2c_remove(struct virtio_device *vdev) 233 { 234 struct virtio_i2c *vi = vdev->priv; 235 236 i2c_del_adapter(&vi->adap); 237 virtio_i2c_del_vqs(vdev); 238 } 239 240 static const struct virtio_device_id id_table[] = { 241 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID }, 242 {} 243 }; 244 MODULE_DEVICE_TABLE(virtio, id_table); 245 246 static int virtio_i2c_freeze(struct virtio_device *vdev) 247 { 248 virtio_i2c_del_vqs(vdev); 249 return 0; 250 } 251 252 static int virtio_i2c_restore(struct virtio_device *vdev) 253 { 254 return virtio_i2c_setup_vqs(vdev->priv); 255 } 256 257 static const unsigned int features[] = { 258 VIRTIO_I2C_F_ZERO_LENGTH_REQUEST, 259 }; 260 261 static struct virtio_driver virtio_i2c_driver = { 262 .feature_table = features, 263 .feature_table_size = ARRAY_SIZE(features), 264 .id_table = id_table, 265 .probe = virtio_i2c_probe, 266 .remove = virtio_i2c_remove, 267 .driver = { 268 .name = "i2c_virtio", 269 }, 270 .freeze = pm_sleep_ptr(virtio_i2c_freeze), 271 .restore = pm_sleep_ptr(virtio_i2c_restore), 272 }; 273 module_virtio_driver(virtio_i2c_driver); 274 275 MODULE_AUTHOR("Jie Deng <jie.deng@intel.com>"); 276 MODULE_AUTHOR("Conghui Chen <conghui.chen@intel.com>"); 277 MODULE_DESCRIPTION("Virtio i2c bus driver"); 278 MODULE_LICENSE("GPL"); 279