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 <log.h>
  12 #include <malloc.h>
  13 #include <asm/gpio.h>
  14
  15 DECLARE_GLOBAL_DATA_PTR;
  16
  17 struct i2c_arbitrator_priv {
  18         struct gpio_desc ap_claim;
  19         struct gpio_desc ec_claim;
  20         uint slew_delay_us;
  21         uint wait_retry_ms;
  22         uint wait_free_ms;
  23 };
  24
  25 int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
  26                             uint channel)
  27 {
  28         struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  29         int ret;
  30
  31         debug("%s: %s\n", __func__, mux->name);
  32         ret = dm_gpio_set_value(&priv->ap_claim, 0);
  33         udelay(priv->slew_delay_us);
  34
  35         return ret;
  36 }
  37
  38 int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
  39                           uint channel)
  40 {
  41         struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
  42         unsigned start;
  43         int ret;
  44
  45         debug("%s: %s\n", __func__, mux->name);
  46         /* Start a round of trying to claim the bus */
  47         start = get_timer(0);
  48         do {
  49                 unsigned start_retry;
  50                 int waiting = 0;
  51
  52                 /* Indicate that we want to claim the bus */
  53                 ret = dm_gpio_set_value(&priv->ap_claim, 1);
  54                 if (ret)
  55                         goto err;
  56                 udelay(priv->slew_delay_us);
  57
  58                 /* Wait for the EC to release it */
  59                 start_retry = get_timer(0);
  60                 while (get_timer(start_retry) < priv->wait_retry_ms) {
  61                         ret = dm_gpio_get_value(&priv->ec_claim);
  62                         if (ret < 0) {
  63                                 goto err;
  64                         } else if (!ret) {
  65                                 /* We got it, so return */
  66                                 return 0;
  67                         }
  68
  69                         if (!waiting)
  70                                 waiting = 1;
  71                 }
  72
  73                 /* It didn't release, so give up, wait, and try again */
  74                 ret = dm_gpio_set_value(&priv->ap_claim, 0);
  75                 if (ret)
  76                         goto err;
  77
  78                 mdelay(priv->wait_retry_ms);
  79         } while (get_timer(start) < priv->wait_free_ms);
  80
  81         /* Give up, release our claim */
  82         printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
  83         ret = -ETIMEDOUT;
  84         ret = 0;
  85 err:
  86         return ret;
  87 }
  88
  89 static int i2c_arbitrator_probe(struct udevice *dev)
  90 {
  91         struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
  92         const void *blob = gd->fdt_blob;
  93         int node = dev_of_offset(dev);
  94         int ret;
  95
  96         debug("%s: %s\n", __func__, dev->name);
  97         priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
  98         priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
  99                 1000;
 100         priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
 101                 1000;
 102         ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
 103                                    GPIOD_IS_OUT);
 104         if (ret)
 105                 goto err;
 106         ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
 107                                    GPIOD_IS_IN);
 108         if (ret)
 109                 goto err_ec_gpio;
 110
 111         return 0;
 112
 113 err_ec_gpio:
 114         dm_gpio_free(dev, &priv->ap_claim);
 115 err:
 116         debug("%s: ret=%d\n", __func__, ret);
 117         return ret;
 118 }
 119
 120 static int i2c_arbitrator_remove(struct udevice *dev)
 121 {
 122         struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
 123
 124         dm_gpio_free(dev, &priv->ap_claim);
 125         dm_gpio_free(dev, &priv->ec_claim);
 126
 127         return 0;
 128 }
 129
 130 static const struct i2c_mux_ops i2c_arbitrator_ops = {
 131         .select         = i2c_arbitrator_select,
 132         .deselect       = i2c_arbitrator_deselect,
 133 };
 134
 135 static const struct udevice_id i2c_arbitrator_ids[] = {
 136         { .compatible = "i2c-arb-gpio-challenge" },
 137         { }
 138 };
 139
 140 U_BOOT_DRIVER(i2c_arbitrator) = {
 141         .name = "i2c_arbitrator",
 142         .id = UCLASS_I2C_MUX,
 143         .of_match = i2c_arbitrator_ids,
 144         .probe = i2c_arbitrator_probe,
 145         .remove = i2c_arbitrator_remove,
 146         .ops = &i2c_arbitrator_ops,
 147         .priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv),
 148 };