drivers/soc/aspeed/aspeed-lpc-snoop.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2017 Google Inc
   4  *
   5  * Provides a simple driver to control the ASPEED LPC snoop interface which
   6  * allows the BMC to listen on and save the data written by
   7  * the host to an arbitrary LPC I/O port.
   8  *
   9  * Typically used by the BMC to "watch" host boot progress via port
  10  * 0x80 writes made by the BIOS during the boot process.
  11  */
  12
  13 #include <linux/bitops.h>
  14 #include <linux/clk.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/fs.h>
  17 #include <linux/kfifo.h>
  18 #include <linux/mfd/syscon.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/module.h>
  21 #include <linux/of.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/poll.h>
  24 #include <linux/regmap.h>
  25
  26 #define DEVICE_NAME     "aspeed-lpc-snoop"
  27
  28 #define NUM_SNOOP_CHANNELS 2
  29 #define SNOOP_FIFO_SIZE 2048
  30
  31 #define HICR5   0x80
  32 #define HICR5_EN_SNP0W          BIT(0)
  33 #define HICR5_ENINT_SNP0W       BIT(1)
  34 #define HICR5_EN_SNP1W          BIT(2)
  35 #define HICR5_ENINT_SNP1W       BIT(3)
  36 #define HICR6   0x84
  37 #define HICR6_STR_SNP0W         BIT(0)
  38 #define HICR6_STR_SNP1W         BIT(1)
  39 #define SNPWADR 0x90
  40 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  41 #define SNPWADR_CH0_SHIFT       0
  42 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  43 #define SNPWADR_CH1_SHIFT       16
  44 #define SNPWDR  0x94
  45 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  46 #define SNPWDR_CH0_SHIFT        0
  47 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  48 #define SNPWDR_CH1_SHIFT        8
  49 #define HICRB   0x100
  50 #define HICRB_ENSNP0D           BIT(14)
  51 #define HICRB_ENSNP1D           BIT(15)
  52
  53 struct aspeed_lpc_snoop_model_data {
  54         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  55          * can use them.
  56          */
  57         unsigned int has_hicrb_ensnp;
  58 };
  59
  60 struct aspeed_lpc_snoop_channel {
  61         struct kfifo            fifo;
  62         wait_queue_head_t       wq;
  63         struct miscdevice       miscdev;
  64 };
  65
  66 struct aspeed_lpc_snoop {
  67         struct regmap           *regmap;
  68         int                     irq;
  69         struct clk              *clk;
  70         struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
  71 };
  72
  73 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
  74 {
  75         return container_of(file->private_data,
  76                             struct aspeed_lpc_snoop_channel,
  77                             miscdev);
  78 }
  79
  80 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
  81                                 size_t count, loff_t *ppos)
  82 {
  83         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
  84         unsigned int copied;
  85         int ret = 0;
  86
  87         if (kfifo_is_empty(&chan->fifo)) {
  88                 if (file->f_flags & O_NONBLOCK)
  89                         return -EAGAIN;
  90                 ret = wait_event_interruptible(chan->wq,
  91                                 !kfifo_is_empty(&chan->fifo));
  92                 if (ret == -ERESTARTSYS)
  93                         return -EINTR;
  94         }
  95         ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
  96         if (ret)
  97                 return ret;
  98
  99         return copied;
 100 }
 101
 102 static __poll_t snoop_file_poll(struct file *file,
 103                                     struct poll_table_struct *pt)
 104 {
 105         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
 106
 107         poll_wait(file, &chan->wq, pt);
 108         return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
 109 }
 110
 111 static const struct file_operations snoop_fops = {
 112         .owner  = THIS_MODULE,
 113         .read   = snoop_file_read,
 114         .poll   = snoop_file_poll,
 115         .llseek = noop_llseek,
 116 };
 117
 118 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
 119 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
 120 {
 121         if (!kfifo_initialized(&chan->fifo))
 122                 return;
 123         if (kfifo_is_full(&chan->fifo))
 124                 kfifo_skip(&chan->fifo);
 125         kfifo_put(&chan->fifo, val);
 126         wake_up_interruptible(&chan->wq);
 127 }
 128
 129 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
 130 {
 131         struct aspeed_lpc_snoop *lpc_snoop = arg;
 132         u32 reg, data;
 133
 134         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
 135                 return IRQ_NONE;
 136
 137         /* Check if one of the snoop channels is interrupting */
 138         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
 139         if (!reg)
 140                 return IRQ_NONE;
 141
 142         /* Ack pending IRQs */
 143         regmap_write(lpc_snoop->regmap, HICR6, reg);
 144
 145         /* Read and save most recent snoop'ed data byte to FIFO */
 146         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
 147
 148         if (reg & HICR6_STR_SNP0W) {
 149                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
 150
 151                 put_fifo_with_discard(&lpc_snoop->chan[0], val);
 152         }
 153         if (reg & HICR6_STR_SNP1W) {
 154                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 155
 156                 put_fifo_with_discard(&lpc_snoop->chan[1], val);
 157         }
 158
 159         return IRQ_HANDLED;
 160 }
 161
 162 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 163                                        struct platform_device *pdev)
 164 {
 165         struct device *dev = &pdev->dev;
 166         int rc;
 167
 168         lpc_snoop->irq = platform_get_irq(pdev, 0);
 169         if (!lpc_snoop->irq)
 170                 return -ENODEV;
 171
 172         rc = devm_request_irq(dev, lpc_snoop->irq,
 173                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 174                               DEVICE_NAME, lpc_snoop);
 175         if (rc < 0) {
 176                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 177                 lpc_snoop->irq = 0;
 178                 return rc;
 179         }
 180
 181         return 0;
 182 }
 183
 184 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 185                                    struct device *dev,
 186                                    int channel, u16 lpc_port)
 187 {
 188         int rc = 0;
 189         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 190         const struct aspeed_lpc_snoop_model_data *model_data =
 191                 of_device_get_match_data(dev);
 192
 193         init_waitqueue_head(&lpc_snoop->chan[channel].wq);
 194         /* Create FIFO datastructure */
 195         rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
 196                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 197         if (rc)
 198                 return rc;
 199
 200         lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
 201         lpc_snoop->chan[channel].miscdev.name =
 202                 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
 203         lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
 204         lpc_snoop->chan[channel].miscdev.parent = dev;
 205         rc = misc_register(&lpc_snoop->chan[channel].miscdev);
 206         if (rc)
 207                 return rc;
 208
 209         /* Enable LPC snoop channel at requested port */
 210         switch (channel) {
 211         case 0:
 212                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 213                 snpwadr_mask = SNPWADR_CH0_MASK;
 214                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 215                 hicrb_en = HICRB_ENSNP0D;
 216                 break;
 217         case 1:
 218                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 219                 snpwadr_mask = SNPWADR_CH1_MASK;
 220                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 221                 hicrb_en = HICRB_ENSNP1D;
 222                 break;
 223         default:
 224                 return -EINVAL;
 225         }
 226
 227         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 228         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 229                            lpc_port << snpwadr_shift);
 230         if (model_data->has_hicrb_ensnp)
 231                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 232                                 hicrb_en, hicrb_en);
 233
 234         return rc;
 235 }
 236
 237 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 238                                      int channel)
 239 {
 240         switch (channel) {
 241         case 0:
 242                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 243                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 244                                    0);
 245                 break;
 246         case 1:
 247                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 248                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 249                                    0);
 250                 break;
 251         default:
 252                 return;
 253         }
 254
 255         kfifo_free(&lpc_snoop->chan[channel].fifo);
 256         misc_deregister(&lpc_snoop->chan[channel].miscdev);
 257 }
 258
 259 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 260 {
 261         struct aspeed_lpc_snoop *lpc_snoop;
 262         struct device *dev;
 263         struct device_node *np;
 264         u32 port;
 265         int rc;
 266
 267         dev = &pdev->dev;
 268
 269         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 270         if (!lpc_snoop)
 271                 return -ENOMEM;
 272
 273         np = pdev->dev.parent->of_node;
 274         if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
 275             !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
 276             !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
 277                 dev_err(dev, "unsupported LPC device binding\n");
 278                 return -ENODEV;
 279         }
 280
 281         lpc_snoop->regmap = syscon_node_to_regmap(np);
 282         if (IS_ERR(lpc_snoop->regmap)) {
 283                 dev_err(dev, "Couldn't get regmap\n");
 284                 return -ENODEV;
 285         }
 286
 287         dev_set_drvdata(&pdev->dev, lpc_snoop);
 288
 289         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 290         if (rc) {
 291                 dev_err(dev, "no snoop ports configured\n");
 292                 return -ENODEV;
 293         }
 294
 295         lpc_snoop->clk = devm_clk_get(dev, NULL);
 296         if (IS_ERR(lpc_snoop->clk)) {
 297                 rc = PTR_ERR(lpc_snoop->clk);
 298                 if (rc != -EPROBE_DEFER)
 299                         dev_err(dev, "couldn't get clock\n");
 300                 return rc;
 301         }
 302         rc = clk_prepare_enable(lpc_snoop->clk);
 303         if (rc) {
 304                 dev_err(dev, "couldn't enable clock\n");
 305                 return rc;
 306         }
 307
 308         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 309         if (rc)
 310                 goto err;
 311
 312         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 313         if (rc)
 314                 goto err;
 315
 316         /* Configuration of 2nd snoop channel port is optional */
 317         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 318                                        1, &port) == 0) {
 319                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 320                 if (rc) {
 321                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 322                         goto err;
 323                 }
 324         }
 325
 326         return 0;
 327
 328 err:
 329         clk_disable_unprepare(lpc_snoop->clk);
 330
 331         return rc;
 332 }
 333
 334 static void aspeed_lpc_snoop_remove(struct platform_device *pdev)
 335 {
 336         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 337
 338         /* Disable both snoop channels */
 339         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 340         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 341
 342         clk_disable_unprepare(lpc_snoop->clk);
 343 }
 344
 345 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
 346         .has_hicrb_ensnp = 0,
 347 };
 348
 349 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
 350         .has_hicrb_ensnp = 1,
 351 };
 352
 353 static const struct of_device_id aspeed_lpc_snoop_match[] = {
 354         { .compatible = "aspeed,ast2400-lpc-snoop",
 355           .data = &ast2400_model_data },
 356         { .compatible = "aspeed,ast2500-lpc-snoop",
 357           .data = &ast2500_model_data },
 358         { .compatible = "aspeed,ast2600-lpc-snoop",
 359           .data = &ast2500_model_data },
 360         { },
 361 };
 362
 363 static struct platform_driver aspeed_lpc_snoop_driver = {
 364         .driver = {
 365                 .name           = DEVICE_NAME,
 366                 .of_match_table = aspeed_lpc_snoop_match,
 367         },
 368         .probe = aspeed_lpc_snoop_probe,
 369         .remove = aspeed_lpc_snoop_remove,
 370 };
 371
 372 module_platform_driver(aspeed_lpc_snoop_driver);
 373
 374 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 375 MODULE_LICENSE("GPL");
 376 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 377 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");