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 * We don't support 0 length messages and so filter out 67 * 0 length transfers by using i2c_adapter_quirks. 68 */ 69 if (!msgs[i].len) 70 break; 71 72 /* 73 * Only 7-bit mode supported for this moment. For the address 74 * format, Please check the Virtio I2C Specification. 75 */ 76 reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); 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 reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1); 85 if (!reqs[i].buf) 86 break; 87 88 sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len); 89 90 if (msgs[i].flags & I2C_M_RD) 91 sgs[outcnt + incnt++] = &msg_buf; 92 else 93 sgs[outcnt++] = &msg_buf; 94 95 sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); 96 sgs[outcnt + incnt++] = &in_hdr; 97 98 if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) { 99 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false); 100 break; 101 } 102 } 103 104 return i; 105 } 106 107 static int virtio_i2c_complete_reqs(struct virtqueue *vq, 108 struct virtio_i2c_req *reqs, 109 struct i2c_msg *msgs, int num, 110 bool timedout) 111 { 112 struct virtio_i2c_req *req; 113 bool failed = timedout; 114 unsigned int len; 115 int i, j = 0; 116 117 for (i = 0; i < num; i++) { 118 /* Detach the ith request from the vq */ 119 req = virtqueue_get_buf(vq, &len); 120 121 /* 122 * Condition req == &reqs[i] should always meet since we have 123 * total num requests in the vq. reqs[i] can never be NULL here. 124 */ 125 if (!failed && (WARN_ON(req != &reqs[i]) || 126 req->in_hdr.status != VIRTIO_I2C_MSG_OK)) 127 failed = true; 128 129 i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], !failed); 130 131 if (!failed) 132 j++; 133 } 134 135 return timedout ? -ETIMEDOUT : j; 136 } 137 138 static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, 139 int num) 140 { 141 struct virtio_i2c *vi = i2c_get_adapdata(adap); 142 struct virtqueue *vq = vi->vq; 143 struct virtio_i2c_req *reqs; 144 unsigned long time_left; 145 int count; 146 147 reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); 148 if (!reqs) 149 return -ENOMEM; 150 151 count = virtio_i2c_prepare_reqs(vq, reqs, msgs, num); 152 if (!count) 153 goto err_free; 154 155 /* 156 * For the case where count < num, i.e. we weren't able to queue all the 157 * msgs, ideally we should abort right away and return early, but some 158 * of the messages are already sent to the remote I2C controller and the 159 * virtqueue will be left in undefined state in that case. We kick the 160 * remote here to clear the virtqueue, so we can try another set of 161 * messages later on. 162 */ 163 164 reinit_completion(&vi->completion); 165 virtqueue_kick(vq); 166 167 time_left = wait_for_completion_timeout(&vi->completion, adap->timeout); 168 if (!time_left) 169 dev_err(&adap->dev, "virtio i2c backend timeout.\n"); 170 171 count = virtio_i2c_complete_reqs(vq, reqs, msgs, count, !time_left); 172 173 err_free: 174 kfree(reqs); 175 return count; 176 } 177 178 static void virtio_i2c_del_vqs(struct virtio_device *vdev) 179 { 180 vdev->config->reset(vdev); 181 vdev->config->del_vqs(vdev); 182 } 183 184 static int virtio_i2c_setup_vqs(struct virtio_i2c *vi) 185 { 186 struct virtio_device *vdev = vi->vdev; 187 188 vi->vq = virtio_find_single_vq(vdev, virtio_i2c_msg_done, "msg"); 189 return PTR_ERR_OR_ZERO(vi->vq); 190 } 191 192 static u32 virtio_i2c_func(struct i2c_adapter *adap) 193 { 194 return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK); 195 } 196 197 static struct i2c_algorithm virtio_algorithm = { 198 .master_xfer = virtio_i2c_xfer, 199 .functionality = virtio_i2c_func, 200 }; 201 202 static const struct i2c_adapter_quirks virtio_i2c_quirks = { 203 .flags = I2C_AQ_NO_ZERO_LEN, 204 }; 205 206 static int virtio_i2c_probe(struct virtio_device *vdev) 207 { 208 struct virtio_i2c *vi; 209 int ret; 210 211 vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL); 212 if (!vi) 213 return -ENOMEM; 214 215 vdev->priv = vi; 216 vi->vdev = vdev; 217 218 init_completion(&vi->completion); 219 220 ret = virtio_i2c_setup_vqs(vi); 221 if (ret) 222 return ret; 223 224 vi->adap.owner = THIS_MODULE; 225 snprintf(vi->adap.name, sizeof(vi->adap.name), 226 "i2c_virtio at virtio bus %d", vdev->index); 227 vi->adap.algo = &virtio_algorithm; 228 vi->adap.quirks = &virtio_i2c_quirks; 229 vi->adap.dev.parent = &vdev->dev; 230 vi->adap.dev.of_node = vdev->dev.of_node; 231 i2c_set_adapdata(&vi->adap, vi); 232 233 /* 234 * Setup ACPI node for controlled devices which will be probed through 235 * ACPI. 236 */ 237 ACPI_COMPANION_SET(&vi->adap.dev, ACPI_COMPANION(vdev->dev.parent)); 238 239 ret = i2c_add_adapter(&vi->adap); 240 if (ret) 241 virtio_i2c_del_vqs(vdev); 242 243 return ret; 244 } 245 246 static void virtio_i2c_remove(struct virtio_device *vdev) 247 { 248 struct virtio_i2c *vi = vdev->priv; 249 250 i2c_del_adapter(&vi->adap); 251 virtio_i2c_del_vqs(vdev); 252 } 253 254 static struct virtio_device_id id_table[] = { 255 { VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID }, 256 {} 257 }; 258 MODULE_DEVICE_TABLE(virtio, id_table); 259 260 #ifdef CONFIG_PM_SLEEP 261 static int virtio_i2c_freeze(struct virtio_device *vdev) 262 { 263 virtio_i2c_del_vqs(vdev); 264 return 0; 265 } 266 267 static int virtio_i2c_restore(struct virtio_device *vdev) 268 { 269 return virtio_i2c_setup_vqs(vdev->priv); 270 } 271 #endif 272 273 static struct virtio_driver virtio_i2c_driver = { 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