drivers/i2c/muxes/i2c-arb-gpio-challenge.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (c) 2015 Google, Inc
   4  * Written by Simon Glass <sjg@chromium.org>
   5  */
   6
   7 #include <common.h>
   8 #include <dm.h>
   9 #include <errno.h>
  10 #include <i2c.h>
  11 #include <asm/gpio.h>
  12
  13 DECLARE_GLOBAL_DATA_PTR;
  14
  15 struct i2c_arbitrator_priv {
  16         struct gpio_desc ap_claim;
  17         struct gpio_desc ec_claim;
  18         uint slew_delay_us;
  19         uint wait_retry_ms;
  20         uint wait_free_ms;
  21 };
  22
  23 int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
  24                             uint channel)
  25 {
  26         struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  27         int ret;
  28
  29         debug("%s: %s\n", __func__, mux->name);
  30         ret = dm_gpio_set_value(&priv->ap_claim, 0);
  31         udelay(priv->slew_delay_us);
  32
  33         return ret;
  34 }
  35
  36 int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
  37                           uint channel)
  38 {
  39         struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  40         unsigned start;
  41         int ret;
  42
  43         debug("%s: %s\n", __func__, mux->name);
  44         /* Start a round of trying to claim the bus */
  45         start = get_timer(0);
  46         do {
  47                 unsigned start_retry;
  48                 int waiting = 0;
  49
  50                 /* Indicate that we want to claim the bus */
  51                 ret = dm_gpio_set_value(&priv->ap_claim, 1);
  52                 if (ret)
  53                         goto err;
  54                 udelay(priv->slew_delay_us);
  55
  56                 /* Wait for the EC to release it */
  57                 start_retry = get_timer(0);
  58                 while (get_timer(start_retry) < priv->wait_retry_ms) {
  59                         ret = dm_gpio_get_value(&priv->ec_claim);
  60                         if (ret < 0) {
  61                                 goto err;
  62                         } else if (!ret) {
  63                                 /* We got it, so return */
  64                                 return 0;
  65                         }
  66
  67                         if (!waiting)
  68                                 waiting = 1;
  69                 }
  70
  71                 /* It didn't release, so give up, wait, and try again */
  72                 ret = dm_gpio_set_value(&priv->ap_claim, 0);
  73                 if (ret)
  74                         goto err;
  75
  76                 mdelay(priv->wait_retry_ms);
  77         } while (get_timer(start) < priv->wait_free_ms);
  78
  79         /* Give up, release our claim */
  80         printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
  81         ret = -ETIMEDOUT;
  82         ret = 0;
  83 err:
  84         return ret;
  85 }
  86
  87 static int i2c_arbitrator_probe(struct udevice *dev)
  88 {
  89         struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
  90         const void *blob = gd->fdt_blob;
  91         int node = dev_of_offset(dev);
  92         int ret;
  93
  94         debug("%s: %s\n", __func__, dev->name);
  95         priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
  96         priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
  97                 1000;
  98         priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
  99                 1000;
 100         ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
 101                                    GPIOD_IS_OUT);
 102         if (ret)
 103                 goto err;
 104         ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
 105                                    GPIOD_IS_IN);
 106         if (ret)
 107                 goto err_ec_gpio;
 108
 109         return 0;
 110
 111 err_ec_gpio:
 112         dm_gpio_free(dev, &priv->ap_claim);
 113 err:
 114         debug("%s: ret=%d\n", __func__, ret);
 115         return ret;
 116 }
 117
 118 static int i2c_arbitrator_remove(struct udevice *dev)
 119 {
 120         struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
 121
 122         dm_gpio_free(dev, &priv->ap_claim);
 123         dm_gpio_free(dev, &priv->ec_claim);
 124
 125         return 0;
 126 }
 127
 128 static const struct i2c_mux_ops i2c_arbitrator_ops = {
 129         .select         = i2c_arbitrator_select,
 130         .deselect       = i2c_arbitrator_deselect,
 131 };
 132
 133 static const struct udevice_id i2c_arbitrator_ids[] = {
 134         { .compatible = "i2c-arb-gpio-challenge" },
 135         { }
 136 };
 137
 138 U_BOOT_DRIVER(i2c_arbitrator) = {
 139         .name = "i2c_arbitrator",
 140         .id = UCLASS_I2C_MUX,
 141         .of_match = i2c_arbitrator_ids,
 142         .probe = i2c_arbitrator_probe,
 143         .remove = i2c_arbitrator_remove,
 144         .ops = &i2c_arbitrator_ops,
 145         .priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv),
 146 };