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/interrupt.h>
  19 #include <linux/kfifo.h>
  20 #include <linux/mfd/syscon.h>
  21 #include <linux/module.h>
  22 #include <linux/of.h>
  23 #include <linux/of_device.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/regmap.h>
  26
  27 #define DEVICE_NAME     "aspeed-lpc-snoop"
  28
  29 #define NUM_SNOOP_CHANNELS 2
  30 #define SNOOP_FIFO_SIZE 2048
  31
  32 #define HICR5   0x0
  33 #define HICR5_EN_SNP0W          BIT(0)
  34 #define HICR5_ENINT_SNP0W       BIT(1)
  35 #define HICR5_EN_SNP1W          BIT(2)
  36 #define HICR5_ENINT_SNP1W       BIT(3)
  37
  38 #define HICR6   0x4
  39 #define HICR6_STR_SNP0W         BIT(0)
  40 #define HICR6_STR_SNP1W         BIT(1)
  41 #define SNPWADR 0x10
  42 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  43 #define SNPWADR_CH0_SHIFT       0
  44 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  45 #define SNPWADR_CH1_SHIFT       16
  46 #define SNPWDR  0x14
  47 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  48 #define SNPWDR_CH0_SHIFT        0
  49 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  50 #define SNPWDR_CH1_SHIFT        8
  51 #define HICRB   0x80
  52 #define HICRB_ENSNP0D           BIT(14)
  53 #define HICRB_ENSNP1D           BIT(15)
  54
  55 struct aspeed_lpc_snoop_model_data {
  56         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  57          * can use them.
  58          */
  59         unsigned int has_hicrb_ensnp;
  60 };
  61
  62 struct aspeed_lpc_snoop {
  63         struct regmap           *regmap;
  64         int                     irq;
  65         struct kfifo            snoop_fifo[NUM_SNOOP_CHANNELS];
  66 };
  67
  68 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
  69 static void put_fifo_with_discard(struct kfifo *fifo, u8 val)
  70 {
  71         if (!kfifo_initialized(fifo))
  72                 return;
  73         if (kfifo_is_full(fifo))
  74                 kfifo_skip(fifo);
  75         kfifo_put(fifo, val);
  76 }
  77
  78 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
  79 {
  80         struct aspeed_lpc_snoop *lpc_snoop = arg;
  81         u32 reg, data;
  82
  83         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
  84                 return IRQ_NONE;
  85
  86         /* Check if one of the snoop channels is interrupting */
  87         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
  88         if (!reg)
  89                 return IRQ_NONE;
  90
  91         /* Ack pending IRQs */
  92         regmap_write(lpc_snoop->regmap, HICR6, reg);
  93
  94         /* Read and save most recent snoop'ed data byte to FIFO */
  95         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
  96
  97         if (reg & HICR6_STR_SNP0W) {
  98                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
  99
 100                 put_fifo_with_discard(&lpc_snoop->snoop_fifo[0], val);
 101         }
 102         if (reg & HICR6_STR_SNP1W) {
 103                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 104
 105                 put_fifo_with_discard(&lpc_snoop->snoop_fifo[1], val);
 106         }
 107
 108         return IRQ_HANDLED;
 109 }
 110
 111 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 112                                        struct platform_device *pdev)
 113 {
 114         struct device *dev = &pdev->dev;
 115         int rc;
 116
 117         lpc_snoop->irq = platform_get_irq(pdev, 0);
 118         if (!lpc_snoop->irq)
 119                 return -ENODEV;
 120
 121         rc = devm_request_irq(dev, lpc_snoop->irq,
 122                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 123                               DEVICE_NAME, lpc_snoop);
 124         if (rc < 0) {
 125                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 126                 lpc_snoop->irq = 0;
 127                 return rc;
 128         }
 129
 130         return 0;
 131 }
 132
 133 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 134                                    struct device *dev,
 135                                    int channel, u16 lpc_port)
 136 {
 137         int rc = 0;
 138         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 139         const struct aspeed_lpc_snoop_model_data *model_data =
 140                 of_device_get_match_data(dev);
 141
 142         /* Create FIFO datastructure */
 143         rc = kfifo_alloc(&lpc_snoop->snoop_fifo[channel],
 144                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 145         if (rc)
 146                 return rc;
 147
 148         /* Enable LPC snoop channel at requested port */
 149         switch (channel) {
 150         case 0:
 151                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 152                 snpwadr_mask = SNPWADR_CH0_MASK;
 153                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 154                 hicrb_en = HICRB_ENSNP0D;
 155                 break;
 156         case 1:
 157                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 158                 snpwadr_mask = SNPWADR_CH1_MASK;
 159                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 160                 hicrb_en = HICRB_ENSNP1D;
 161                 break;
 162         default:
 163                 return -EINVAL;
 164         }
 165
 166         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 167         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 168                            lpc_port << snpwadr_shift);
 169         if (model_data->has_hicrb_ensnp)
 170                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 171                                 hicrb_en, hicrb_en);
 172
 173         return rc;
 174 }
 175
 176 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 177                                      int channel)
 178 {
 179         switch (channel) {
 180         case 0:
 181                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 182                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 183                                    0);
 184                 break;
 185         case 1:
 186                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 187                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 188                                    0);
 189                 break;
 190         default:
 191                 return;
 192         }
 193
 194         kfifo_free(&lpc_snoop->snoop_fifo[channel]);
 195 }
 196
 197 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 198 {
 199         struct aspeed_lpc_snoop *lpc_snoop;
 200         struct device *dev;
 201         u32 port;
 202         int rc;
 203
 204         dev = &pdev->dev;
 205
 206         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 207         if (!lpc_snoop)
 208                 return -ENOMEM;
 209
 210         lpc_snoop->regmap = syscon_node_to_regmap(
 211                         pdev->dev.parent->of_node);
 212         if (IS_ERR(lpc_snoop->regmap)) {
 213                 dev_err(dev, "Couldn't get regmap\n");
 214                 return -ENODEV;
 215         }
 216
 217         dev_set_drvdata(&pdev->dev, lpc_snoop);
 218
 219         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 220         if (rc) {
 221                 dev_err(dev, "no snoop ports configured\n");
 222                 return -ENODEV;
 223         }
 224
 225         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 226         if (rc)
 227                 return rc;
 228
 229         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 230         if (rc)
 231                 return rc;
 232
 233         /* Configuration of 2nd snoop channel port is optional */
 234         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 235                                        1, &port) == 0) {
 236                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 237                 if (rc)
 238                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 239         }
 240
 241         return rc;
 242 }
 243
 244 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
 245 {
 246         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 247
 248         /* Disable both snoop channels */
 249         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 250         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 251
 252         return 0;
 253 }
 254
 255 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
 256         .has_hicrb_ensnp = 0,
 257 };
 258
 259 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
 260         .has_hicrb_ensnp = 1,
 261 };
 262
 263 static const struct of_device_id aspeed_lpc_snoop_match[] = {
 264         { .compatible = "aspeed,ast2400-lpc-snoop",
 265           .data = &ast2400_model_data },
 266         { .compatible = "aspeed,ast2500-lpc-snoop",
 267           .data = &ast2500_model_data },
 268         { },
 269 };
 270
 271 static struct platform_driver aspeed_lpc_snoop_driver = {
 272         .driver = {
 273                 .name           = DEVICE_NAME,
 274                 .of_match_table = aspeed_lpc_snoop_match,
 275         },
 276         .probe = aspeed_lpc_snoop_probe,
 277         .remove = aspeed_lpc_snoop_remove,
 278 };
 279
 280 module_platform_driver(aspeed_lpc_snoop_driver);
 281
 282 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 283 MODULE_LICENSE("GPL");
 284 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 285 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");