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/interrupt.h>
  15 #include <linux/fs.h>
  16 #include <linux/kfifo.h>
  17 #include <linux/mfd/syscon.h>
  18 #include <linux/miscdevice.h>
  19 #include <linux/module.h>
  20 #include <linux/of.h>
  21 #include <linux/of_device.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   0x0
  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
  37 #define HICR6   0x4
  38 #define HICR6_STR_SNP0W         BIT(0)
  39 #define HICR6_STR_SNP1W         BIT(1)
  40 #define SNPWADR 0x10
  41 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  42 #define SNPWADR_CH0_SHIFT       0
  43 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  44 #define SNPWADR_CH1_SHIFT       16
  45 #define SNPWDR  0x14
  46 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  47 #define SNPWDR_CH0_SHIFT        0
  48 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  49 #define SNPWDR_CH1_SHIFT        8
  50 #define HICRB   0x80
  51 #define HICRB_ENSNP0D           BIT(14)
  52 #define HICRB_ENSNP1D           BIT(15)
  53
  54 struct aspeed_lpc_snoop_model_data {
  55         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  56          * can use them.
  57          */
  58         unsigned int has_hicrb_ensnp;
  59 };
  60
  61 struct aspeed_lpc_snoop_channel {
  62         struct kfifo            fifo;
  63         wait_queue_head_t       wq;
  64         struct miscdevice       miscdev;
  65 };
  66
  67 struct aspeed_lpc_snoop {
  68         struct regmap           *regmap;
  69         int                     irq;
  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
  97         return ret ? ret : copied;
  98 }
  99
 100 static unsigned int snoop_file_poll(struct file *file,
 101                                     struct poll_table_struct *pt)
 102 {
 103         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
 104
 105         poll_wait(file, &chan->wq, pt);
 106         return !kfifo_is_empty(&chan->fifo) ? POLLIN : 0;
 107 }
 108
 109 static const struct file_operations snoop_fops = {
 110         .owner  = THIS_MODULE,
 111         .read   = snoop_file_read,
 112         .poll   = snoop_file_poll,
 113         .llseek = noop_llseek,
 114 };
 115
 116 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
 117 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
 118 {
 119         if (!kfifo_initialized(&chan->fifo))
 120                 return;
 121         if (kfifo_is_full(&chan->fifo))
 122                 kfifo_skip(&chan->fifo);
 123         kfifo_put(&chan->fifo, val);
 124         wake_up_interruptible(&chan->wq);
 125 }
 126
 127 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
 128 {
 129         struct aspeed_lpc_snoop *lpc_snoop = arg;
 130         u32 reg, data;
 131
 132         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
 133                 return IRQ_NONE;
 134
 135         /* Check if one of the snoop channels is interrupting */
 136         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
 137         if (!reg)
 138                 return IRQ_NONE;
 139
 140         /* Ack pending IRQs */
 141         regmap_write(lpc_snoop->regmap, HICR6, reg);
 142
 143         /* Read and save most recent snoop'ed data byte to FIFO */
 144         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
 145
 146         if (reg & HICR6_STR_SNP0W) {
 147                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
 148
 149                 put_fifo_with_discard(&lpc_snoop->chan[0], val);
 150         }
 151         if (reg & HICR6_STR_SNP1W) {
 152                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 153
 154                 put_fifo_with_discard(&lpc_snoop->chan[1], val);
 155         }
 156
 157         return IRQ_HANDLED;
 158 }
 159
 160 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 161                                        struct platform_device *pdev)
 162 {
 163         struct device *dev = &pdev->dev;
 164         int rc;
 165
 166         lpc_snoop->irq = platform_get_irq(pdev, 0);
 167         if (!lpc_snoop->irq)
 168                 return -ENODEV;
 169
 170         rc = devm_request_irq(dev, lpc_snoop->irq,
 171                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 172                               DEVICE_NAME, lpc_snoop);
 173         if (rc < 0) {
 174                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 175                 lpc_snoop->irq = 0;
 176                 return rc;
 177         }
 178
 179         return 0;
 180 }
 181
 182 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 183                                    struct device *dev,
 184                                    int channel, u16 lpc_port)
 185 {
 186         int rc = 0;
 187         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 188         const struct aspeed_lpc_snoop_model_data *model_data =
 189                 of_device_get_match_data(dev);
 190
 191         init_waitqueue_head(&lpc_snoop->chan[channel].wq);
 192         /* Create FIFO datastructure */
 193         rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
 194                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 195         if (rc)
 196                 return rc;
 197
 198         lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
 199         lpc_snoop->chan[channel].miscdev.name =
 200                 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
 201         lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
 202         lpc_snoop->chan[channel].miscdev.parent = dev;
 203         rc = misc_register(&lpc_snoop->chan[channel].miscdev);
 204         if (rc)
 205                 return rc;
 206
 207         /* Enable LPC snoop channel at requested port */
 208         switch (channel) {
 209         case 0:
 210                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 211                 snpwadr_mask = SNPWADR_CH0_MASK;
 212                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 213                 hicrb_en = HICRB_ENSNP0D;
 214                 break;
 215         case 1:
 216                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 217                 snpwadr_mask = SNPWADR_CH1_MASK;
 218                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 219                 hicrb_en = HICRB_ENSNP1D;
 220                 break;
 221         default:
 222                 return -EINVAL;
 223         }
 224
 225         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 226         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 227                            lpc_port << snpwadr_shift);
 228         if (model_data->has_hicrb_ensnp)
 229                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 230                                 hicrb_en, hicrb_en);
 231
 232         return rc;
 233 }
 234
 235 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 236                                      int channel)
 237 {
 238         switch (channel) {
 239         case 0:
 240                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 241                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 242                                    0);
 243                 break;
 244         case 1:
 245                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 246                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 247                                    0);
 248                 break;
 249         default:
 250                 return;
 251         }
 252
 253         kfifo_free(&lpc_snoop->chan[channel].fifo);
 254         misc_deregister(&lpc_snoop->chan[channel].miscdev);
 255 }
 256
 257 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 258 {
 259         struct aspeed_lpc_snoop *lpc_snoop;
 260         struct device *dev;
 261         u32 port;
 262         int rc;
 263
 264         dev = &pdev->dev;
 265
 266         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 267         if (!lpc_snoop)
 268                 return -ENOMEM;
 269
 270         lpc_snoop->regmap = syscon_node_to_regmap(
 271                         pdev->dev.parent->of_node);
 272         if (IS_ERR(lpc_snoop->regmap)) {
 273                 dev_err(dev, "Couldn't get regmap\n");
 274                 return -ENODEV;
 275         }
 276
 277         dev_set_drvdata(&pdev->dev, lpc_snoop);
 278
 279         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 280         if (rc) {
 281                 dev_err(dev, "no snoop ports configured\n");
 282                 return -ENODEV;
 283         }
 284
 285         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 286         if (rc)
 287                 return rc;
 288
 289         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 290         if (rc)
 291                 return rc;
 292
 293         /* Configuration of 2nd snoop channel port is optional */
 294         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 295                                        1, &port) == 0) {
 296                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 297                 if (rc)
 298                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 299         }
 300
 301         return rc;
 302 }
 303
 304 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
 305 {
 306         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 307
 308         /* Disable both snoop channels */
 309         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 310         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 311
 312         return 0;
 313 }
 314
 315 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
 316         .has_hicrb_ensnp = 0,
 317 };
 318
 319 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
 320         .has_hicrb_ensnp = 1,
 321 };
 322
 323 static const struct of_device_id aspeed_lpc_snoop_match[] = {
 324         { .compatible = "aspeed,ast2400-lpc-snoop",
 325           .data = &ast2400_model_data },
 326         { .compatible = "aspeed,ast2500-lpc-snoop",
 327           .data = &ast2500_model_data },
 328         { },
 329 };
 330
 331 static struct platform_driver aspeed_lpc_snoop_driver = {
 332         .driver = {
 333                 .name           = DEVICE_NAME,
 334                 .of_match_table = aspeed_lpc_snoop_match,
 335         },
 336         .probe = aspeed_lpc_snoop_probe,
 337         .remove = aspeed_lpc_snoop_remove,
 338 };
 339
 340 module_platform_driver(aspeed_lpc_snoop_driver);
 341
 342 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 343 MODULE_LICENSE("GPL");
 344 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 345 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");