drivers/misc/aspeed-lpc-snoop.c

   1 /*
   2  * Copyright 2017 Google Inc
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  *
   9  * Provides a simple driver to control the ASPEED LPC snoop interface which
  10  * allows the BMC to listen on and save the data written by
  11  * the host to an arbitrary LPC I/O port.
  12  *
  13  * Typically used by the BMC to "watch" host boot progress via port
  14  * 0x80 writes made by the BIOS during the boot process.
  15  */
  16
  17 #include <linux/bitops.h>
  18 #include <linux/clk.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/fs.h>
  21 #include <linux/kfifo.h>
  22 #include <linux/mfd/syscon.h>
  23 #include <linux/miscdevice.h>
  24 #include <linux/module.h>
  25 #include <linux/of.h>
  26 #include <linux/of_device.h>
  27 #include <linux/platform_device.h>
  28 #include <linux/poll.h>
  29 #include <linux/regmap.h>
  30
  31 #define DEVICE_NAME     "aspeed-lpc-snoop"
  32
  33 #define NUM_SNOOP_CHANNELS 2
  34 #define SNOOP_FIFO_SIZE 2048
  35
  36 #define HICR5   0x0
  37 #define HICR5_EN_SNP0W          BIT(0)
  38 #define HICR5_ENINT_SNP0W       BIT(1)
  39 #define HICR5_EN_SNP1W          BIT(2)
  40 #define HICR5_ENINT_SNP1W       BIT(3)
  41
  42 #define HICR6   0x4
  43 #define HICR6_STR_SNP0W         BIT(0)
  44 #define HICR6_STR_SNP1W         BIT(1)
  45 #define SNPWADR 0x10
  46 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  47 #define SNPWADR_CH0_SHIFT       0
  48 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  49 #define SNPWADR_CH1_SHIFT       16
  50 #define SNPWDR  0x14
  51 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  52 #define SNPWDR_CH0_SHIFT        0
  53 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  54 #define SNPWDR_CH1_SHIFT        8
  55 #define HICRB   0x80
  56 #define HICRB_ENSNP0D           BIT(14)
  57 #define HICRB_ENSNP1D           BIT(15)
  58
  59 struct aspeed_lpc_snoop_model_data {
  60         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  61          * can use them.
  62          */
  63         unsigned int has_hicrb_ensnp;
  64 };
  65
  66 struct aspeed_lpc_snoop_channel {
  67         struct kfifo            fifo;
  68         wait_queue_head_t       wq;
  69         struct miscdevice       miscdev;
  70 };
  71
  72 struct aspeed_lpc_snoop {
  73         struct regmap           *regmap;
  74         int                     irq;
  75         struct clk              *clk;
  76         struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
  77 };
  78
  79 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
  80 {
  81         return container_of(file->private_data,
  82                             struct aspeed_lpc_snoop_channel,
  83                             miscdev);
  84 }
  85
  86 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
  87                                 size_t count, loff_t *ppos)
  88 {
  89         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
  90         unsigned int copied;
  91         int ret = 0;
  92
  93         if (kfifo_is_empty(&chan->fifo)) {
  94                 if (file->f_flags & O_NONBLOCK)
  95                         return -EAGAIN;
  96                 ret = wait_event_interruptible(chan->wq,
  97                                 !kfifo_is_empty(&chan->fifo));
  98                 if (ret == -ERESTARTSYS)
  99                         return -EINTR;
 100         }
 101         ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
 102         if (ret)
 103                 return ret;
 104
 105         return copied;
 106 }
 107
 108 static __poll_t snoop_file_poll(struct file *file,
 109                                     struct poll_table_struct *pt)
 110 {
 111         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
 112
 113         poll_wait(file, &chan->wq, pt);
 114         return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
 115 }
 116
 117 static const struct file_operations snoop_fops = {
 118         .owner  = THIS_MODULE,
 119         .read   = snoop_file_read,
 120         .poll   = snoop_file_poll,
 121         .llseek = noop_llseek,
 122 };
 123
 124 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
 125 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
 126 {
 127         if (!kfifo_initialized(&chan->fifo))
 128                 return;
 129         if (kfifo_is_full(&chan->fifo))
 130                 kfifo_skip(&chan->fifo);
 131         kfifo_put(&chan->fifo, val);
 132         wake_up_interruptible(&chan->wq);
 133 }
 134
 135 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
 136 {
 137         struct aspeed_lpc_snoop *lpc_snoop = arg;
 138         u32 reg, data;
 139
 140         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
 141                 return IRQ_NONE;
 142
 143         /* Check if one of the snoop channels is interrupting */
 144         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
 145         if (!reg)
 146                 return IRQ_NONE;
 147
 148         /* Ack pending IRQs */
 149         regmap_write(lpc_snoop->regmap, HICR6, reg);
 150
 151         /* Read and save most recent snoop'ed data byte to FIFO */
 152         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
 153
 154         if (reg & HICR6_STR_SNP0W) {
 155                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
 156
 157                 put_fifo_with_discard(&lpc_snoop->chan[0], val);
 158         }
 159         if (reg & HICR6_STR_SNP1W) {
 160                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 161
 162                 put_fifo_with_discard(&lpc_snoop->chan[1], val);
 163         }
 164
 165         return IRQ_HANDLED;
 166 }
 167
 168 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 169                                        struct platform_device *pdev)
 170 {
 171         struct device *dev = &pdev->dev;
 172         int rc;
 173
 174         lpc_snoop->irq = platform_get_irq(pdev, 0);
 175         if (!lpc_snoop->irq)
 176                 return -ENODEV;
 177
 178         rc = devm_request_irq(dev, lpc_snoop->irq,
 179                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 180                               DEVICE_NAME, lpc_snoop);
 181         if (rc < 0) {
 182                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 183                 lpc_snoop->irq = 0;
 184                 return rc;
 185         }
 186
 187         return 0;
 188 }
 189
 190 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 191                                    struct device *dev,
 192                                    int channel, u16 lpc_port)
 193 {
 194         int rc = 0;
 195         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 196         const struct aspeed_lpc_snoop_model_data *model_data =
 197                 of_device_get_match_data(dev);
 198
 199         init_waitqueue_head(&lpc_snoop->chan[channel].wq);
 200         /* Create FIFO datastructure */
 201         rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
 202                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 203         if (rc)
 204                 return rc;
 205
 206         lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
 207         lpc_snoop->chan[channel].miscdev.name =
 208                 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
 209         lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
 210         lpc_snoop->chan[channel].miscdev.parent = dev;
 211         rc = misc_register(&lpc_snoop->chan[channel].miscdev);
 212         if (rc)
 213                 return rc;
 214
 215         /* Enable LPC snoop channel at requested port */
 216         switch (channel) {
 217         case 0:
 218                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 219                 snpwadr_mask = SNPWADR_CH0_MASK;
 220                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 221                 hicrb_en = HICRB_ENSNP0D;
 222                 break;
 223         case 1:
 224                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 225                 snpwadr_mask = SNPWADR_CH1_MASK;
 226                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 227                 hicrb_en = HICRB_ENSNP1D;
 228                 break;
 229         default:
 230                 return -EINVAL;
 231         }
 232
 233         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 234         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 235                            lpc_port << snpwadr_shift);
 236         if (model_data->has_hicrb_ensnp)
 237                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 238                                 hicrb_en, hicrb_en);
 239
 240         return rc;
 241 }
 242
 243 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 244                                      int channel)
 245 {
 246         switch (channel) {
 247         case 0:
 248                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 249                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 250                                    0);
 251                 break;
 252         case 1:
 253                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 254                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 255                                    0);
 256                 break;
 257         default:
 258                 return;
 259         }
 260
 261         kfifo_free(&lpc_snoop->chan[channel].fifo);
 262         misc_deregister(&lpc_snoop->chan[channel].miscdev);
 263 }
 264
 265 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 266 {
 267         struct aspeed_lpc_snoop *lpc_snoop;
 268         struct device *dev;
 269         u32 port;
 270         int rc;
 271
 272         dev = &pdev->dev;
 273
 274         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 275         if (!lpc_snoop)
 276                 return -ENOMEM;
 277
 278         lpc_snoop->regmap = syscon_node_to_regmap(
 279                         pdev->dev.parent->of_node);
 280         if (IS_ERR(lpc_snoop->regmap)) {
 281                 dev_err(dev, "Couldn't get regmap\n");
 282                 return -ENODEV;
 283         }
 284
 285         dev_set_drvdata(&pdev->dev, lpc_snoop);
 286
 287         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 288         if (rc) {
 289                 dev_err(dev, "no snoop ports configured\n");
 290                 return -ENODEV;
 291         }
 292
 293         lpc_snoop->clk = devm_clk_get(dev, NULL);
 294         if (IS_ERR(lpc_snoop->clk)) {
 295                 rc = PTR_ERR(lpc_snoop->clk);
 296                 if (rc != -EPROBE_DEFER)
 297                         dev_err(dev, "couldn't get clock\n");
 298                 return rc;
 299         }
 300         rc = clk_prepare_enable(lpc_snoop->clk);
 301         if (rc) {
 302                 dev_err(dev, "couldn't enable clock\n");
 303                 return rc;
 304         }
 305
 306         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 307         if (rc)
 308                 goto err;
 309
 310         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 311         if (rc)
 312                 goto err;
 313
 314         /* Configuration of 2nd snoop channel port is optional */
 315         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 316                                        1, &port) == 0) {
 317                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 318                 if (rc) {
 319                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 320                         goto err;
 321                 }
 322         }
 323
 324         return 0;
 325
 326 err:
 327         clk_disable_unprepare(lpc_snoop->clk);
 328
 329         return rc;
 330 }
 331
 332 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
 333 {
 334         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 335
 336         /* Disable both snoop channels */
 337         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 338         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 339
 340         clk_disable_unprepare(lpc_snoop->clk);
 341
 342         return 0;
 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         { },
 359 };
 360
 361 static struct platform_driver aspeed_lpc_snoop_driver = {
 362         .driver = {
 363                 .name           = DEVICE_NAME,
 364                 .of_match_table = aspeed_lpc_snoop_match,
 365         },
 366         .probe = aspeed_lpc_snoop_probe,
 367         .remove = aspeed_lpc_snoop_remove,
 368 };
 369
 370 module_platform_driver(aspeed_lpc_snoop_driver);
 371
 372 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 373 MODULE_LICENSE("GPL");
 374 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 375 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");