avionic design with actual uboot and tooling

submodule of avionic design uboot bootloader and with included tools to
get you started , read readme.md and readme-tk1-loader.md

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

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <i2c.h>
+#include <asm/gpio.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct i2c_arbitrator_priv {
+	struct gpio_desc ap_claim;
+	struct gpio_desc ec_claim;
+	uint slew_delay_us;
+	uint wait_retry_ms;
+	uint wait_free_ms;
+};
+
+int i2c_arbitrator_deselect(struct udevice *mux, struct udevice *bus,
+			    uint channel)
+{
+	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
+	int ret;
+
+	debug("%s: %s\n", __func__, mux->name);
+	ret = dm_gpio_set_value(&priv->ap_claim, 0);
+	udelay(priv->slew_delay_us);
+
+	return ret;
+}
+
+int i2c_arbitrator_select(struct udevice *mux, struct udevice *bus,
+			  uint channel)
+{
+	struct i2c_arbitrator_priv *priv = dev_get_priv(mux);
+	unsigned start;
+	int ret;
+
+	debug("%s: %s\n", __func__, mux->name);
+	/* Start a round of trying to claim the bus */
+	start = get_timer(0);
+	do {
+		unsigned start_retry;
+		int waiting = 0;
+
+		/* Indicate that we want to claim the bus */
+		ret = dm_gpio_set_value(&priv->ap_claim, 1);
+		if (ret)
+			goto err;
+		udelay(priv->slew_delay_us);
+
+		/* Wait for the EC to release it */
+		start_retry = get_timer(0);
+		while (get_timer(start_retry) < priv->wait_retry_ms) {
+			ret = dm_gpio_get_value(&priv->ec_claim);
+			if (ret < 0) {
+				goto err;
+			} else if (!ret) {
+				/* We got it, so return */
+				return 0;
+			}
+
+			if (!waiting)
+				waiting = 1;
+		}
+
+		/* It didn't release, so give up, wait, and try again */
+		ret = dm_gpio_set_value(&priv->ap_claim, 0);
+		if (ret)
+			goto err;
+
+		mdelay(priv->wait_retry_ms);
+	} while (get_timer(start) < priv->wait_free_ms);
+
+	/* Give up, release our claim */
+	printf("I2C: Could not claim bus, timeout %lu\n", get_timer(start));
+	ret = -ETIMEDOUT;
+	ret = 0;
+err:
+	return ret;
+}
+
+static int i2c_arbitrator_probe(struct udevice *dev)
+{
+	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
+	const void *blob = gd->fdt_blob;
+	int node = dev->of_offset;
+	int ret;
+
+	debug("%s: %s\n", __func__, dev->name);
+	priv->slew_delay_us = fdtdec_get_int(blob, node, "slew-delay-us", 0);
+	priv->wait_retry_ms = fdtdec_get_int(blob, node, "wait-retry-us", 0) /
+		1000;
+	priv->wait_free_ms = fdtdec_get_int(blob, node, "wait-free-us", 0) /
+		1000;
+	ret = gpio_request_by_name(dev, "our-claim-gpio", 0, &priv->ap_claim,
+				   GPIOD_IS_OUT);
+	if (ret)
+		goto err;
+	ret = gpio_request_by_name(dev, "their-claim-gpios", 0, &priv->ec_claim,
+				   GPIOD_IS_IN);
+	if (ret)
+		goto err_ec_gpio;
+
+	return 0;
+
+err_ec_gpio:
+	dm_gpio_free(dev, &priv->ap_claim);
+err:
+	debug("%s: ret=%d\n", __func__, ret);
+	return ret;
+}
+
+static int i2c_arbitrator_remove(struct udevice *dev)
+{
+	struct i2c_arbitrator_priv *priv = dev_get_priv(dev);
+
+	dm_gpio_free(dev, &priv->ap_claim);
+	dm_gpio_free(dev, &priv->ec_claim);
+
+	return 0;
+}
+
+static const struct i2c_mux_ops i2c_arbitrator_ops = {
+	.select		= i2c_arbitrator_select,
+	.deselect	= i2c_arbitrator_deselect,
+};
+
+static const struct udevice_id i2c_arbitrator_ids[] = {
+	{ .compatible = "i2c-arb-gpio-challenge" },
+	{ }
+};
+
+U_BOOT_DRIVER(i2c_arbitrator) = {
+	.name = "i2c_arbitrator",
+	.id = UCLASS_I2C_MUX,
+	.of_match = i2c_arbitrator_ids,
+	.probe = i2c_arbitrator_probe,
+	.remove = i2c_arbitrator_remove,
+	.ops = &i2c_arbitrator_ops,
+	.priv_auto_alloc_size = sizeof(struct i2c_arbitrator_priv),
+};