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