![Linus Torvalds](/assets/img/avatar_default.png)
Pull i2c updates from Wolfram Sang: "New stuff from the I2C world: - in the core, getting irqs from ACPI is now similar to OF - new driver for MediaTek MT7621/7628/7688 SoCs - bcm2835, i801, and tegra drivers got some more attention - GPIO API cleanups - cleanups in the core headers - lots of usual driver updates" * 'i2c/for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: (74 commits) i2c: mt7621: Fix platform_no_drv_owner.cocci warnings i2c: cpm: remove casting dma_alloc dt-bindings: i2c: sun6i-p2wi: Fix the binding example dt-bindings: i2c: mv64xxx: Fix the example compatible i2c: i801: Documentation update i2c: i801: Add support for Intel Tiger Lake i2c: i801: Fix PCI ID sorting dt-bindings: i2c-stm32: document optional dmas i2c: i2c-stm32f7: Add I2C_SMBUS_I2C_BLOCK_DATA support i2c: core: Tidy up handling of init_irq i2c: core: Move ACPI gpio IRQ handling into i2c_acpi_get_irq i2c: core: Move ACPI IRQ handling to probe time i2c: acpi: Factor out getting the IRQ from ACPI i2c: acpi: Use available IRQ helper functions i2c: core: Allow whole core to use i2c_dev_irq_from_resources eeprom: at24: modify a comment referring to platform data dt-bindings: i2c: omap: Add new compatible for J721E SoCs dt-bindings: i2c: mv64xxx: Add YAML schemas dt-bindings: i2c: sun6i-p2wi: Add YAML schemas i2c: mt7621: Add MediaTek MT7621/7628/7688 I2C driver ...
207 lines
5.6 KiB
C
207 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* GPIO-based I2C Arbitration Using a Challenge & Response Mechanism
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*
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* Copyright (C) 2012 Google, Inc
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*/
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#include <linux/delay.h>
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#include <linux/gpio/consumer.h>
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#include <linux/kernel.h>
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#include <linux/i2c.h>
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#include <linux/i2c-mux.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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/**
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* struct i2c_arbitrator_data - Driver data for I2C arbitrator
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*
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* @our_gpio: GPIO descriptor we'll use to claim.
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* @their_gpio: GPIO descriptor that the other side will use to claim.
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* @slew_delay_us: microseconds to wait for a GPIO to go high.
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* @wait_retry_us: we'll attempt another claim after this many microseconds.
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* @wait_free_us: we'll give up after this many microseconds.
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*/
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struct i2c_arbitrator_data {
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struct gpio_desc *our_gpio;
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struct gpio_desc *their_gpio;
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unsigned int slew_delay_us;
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unsigned int wait_retry_us;
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unsigned int wait_free_us;
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};
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/**
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* i2c_arbitrator_select - claim the I2C bus
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*
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* Use the GPIO-based signalling protocol; return -EBUSY if we fail.
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*/
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static int i2c_arbitrator_select(struct i2c_mux_core *muxc, u32 chan)
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{
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const struct i2c_arbitrator_data *arb = i2c_mux_priv(muxc);
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unsigned long stop_retry, stop_time;
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/* Start a round of trying to claim the bus */
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stop_time = jiffies + usecs_to_jiffies(arb->wait_free_us) + 1;
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do {
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/* Indicate that we want to claim the bus */
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gpiod_set_value(arb->our_gpio, 1);
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udelay(arb->slew_delay_us);
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/* Wait for the other master to release it */
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stop_retry = jiffies + usecs_to_jiffies(arb->wait_retry_us) + 1;
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while (time_before(jiffies, stop_retry)) {
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int gpio_val = gpiod_get_value(arb->their_gpio);
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if (!gpio_val) {
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/* We got it, so return */
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return 0;
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}
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usleep_range(50, 200);
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}
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/* It didn't release, so give up, wait, and try again */
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gpiod_set_value(arb->our_gpio, 0);
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usleep_range(arb->wait_retry_us, arb->wait_retry_us * 2);
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} while (time_before(jiffies, stop_time));
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/* Give up, release our claim */
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gpiod_set_value(arb->our_gpio, 0);
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udelay(arb->slew_delay_us);
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dev_err(muxc->dev, "Could not claim bus, timeout\n");
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return -EBUSY;
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}
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/**
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* i2c_arbitrator_deselect - release the I2C bus
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*
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* Release the I2C bus using the GPIO-based signalling protocol.
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*/
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static int i2c_arbitrator_deselect(struct i2c_mux_core *muxc, u32 chan)
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{
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const struct i2c_arbitrator_data *arb = i2c_mux_priv(muxc);
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/* Release the bus and wait for the other master to notice */
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gpiod_set_value(arb->our_gpio, 0);
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udelay(arb->slew_delay_us);
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return 0;
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}
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static int i2c_arbitrator_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct device_node *np = dev->of_node;
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struct device_node *parent_np;
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struct i2c_mux_core *muxc;
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struct i2c_arbitrator_data *arb;
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struct gpio_desc *dummy;
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int ret;
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/* We only support probing from device tree; no platform_data */
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if (!np) {
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dev_err(dev, "Cannot find device tree node\n");
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return -ENODEV;
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}
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if (dev_get_platdata(dev)) {
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dev_err(dev, "Platform data is not supported\n");
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return -EINVAL;
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}
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muxc = i2c_mux_alloc(NULL, dev, 1, sizeof(*arb), I2C_MUX_ARBITRATOR,
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i2c_arbitrator_select, i2c_arbitrator_deselect);
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if (!muxc)
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return -ENOMEM;
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arb = i2c_mux_priv(muxc);
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platform_set_drvdata(pdev, muxc);
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/* Request GPIOs, our GPIO as unclaimed to begin with */
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arb->our_gpio = devm_gpiod_get(dev, "our-claim", GPIOD_OUT_LOW);
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if (IS_ERR(arb->our_gpio)) {
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dev_err(dev, "could not get \"our-claim\" GPIO (%ld)\n",
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PTR_ERR(arb->our_gpio));
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return PTR_ERR(arb->our_gpio);
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}
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arb->their_gpio = devm_gpiod_get(dev, "their-claim", GPIOD_IN);
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if (IS_ERR(arb->their_gpio)) {
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dev_err(dev, "could not get \"their-claim\" GPIO (%ld)\n",
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PTR_ERR(arb->their_gpio));
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return PTR_ERR(arb->their_gpio);
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}
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/* At the moment we only support a single two master (us + 1 other) */
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dummy = devm_gpiod_get_index(dev, "their-claim", 1, GPIOD_IN);
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if (!IS_ERR(dummy)) {
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dev_err(dev, "Only one other master is supported\n");
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return -EINVAL;
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} else if (PTR_ERR(dummy) == -EPROBE_DEFER) {
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return -EPROBE_DEFER;
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}
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/* Arbitration parameters */
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if (of_property_read_u32(np, "slew-delay-us", &arb->slew_delay_us))
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arb->slew_delay_us = 10;
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if (of_property_read_u32(np, "wait-retry-us", &arb->wait_retry_us))
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arb->wait_retry_us = 3000;
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if (of_property_read_u32(np, "wait-free-us", &arb->wait_free_us))
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arb->wait_free_us = 50000;
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/* Find our parent */
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parent_np = of_parse_phandle(np, "i2c-parent", 0);
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if (!parent_np) {
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dev_err(dev, "Cannot parse i2c-parent\n");
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return -EINVAL;
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}
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muxc->parent = of_get_i2c_adapter_by_node(parent_np);
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of_node_put(parent_np);
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if (!muxc->parent) {
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dev_err(dev, "Cannot find parent bus\n");
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return -EPROBE_DEFER;
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}
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/* Actually add the mux adapter */
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ret = i2c_mux_add_adapter(muxc, 0, 0, 0);
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if (ret)
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i2c_put_adapter(muxc->parent);
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return ret;
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}
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static int i2c_arbitrator_remove(struct platform_device *pdev)
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{
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struct i2c_mux_core *muxc = platform_get_drvdata(pdev);
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i2c_mux_del_adapters(muxc);
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i2c_put_adapter(muxc->parent);
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return 0;
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}
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static const struct of_device_id i2c_arbitrator_of_match[] = {
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{ .compatible = "i2c-arb-gpio-challenge", },
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{},
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};
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MODULE_DEVICE_TABLE(of, i2c_arbitrator_of_match);
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static struct platform_driver i2c_arbitrator_driver = {
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.probe = i2c_arbitrator_probe,
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.remove = i2c_arbitrator_remove,
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.driver = {
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.name = "i2c-arb-gpio-challenge",
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.of_match_table = i2c_arbitrator_of_match,
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},
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};
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module_platform_driver(i2c_arbitrator_driver);
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MODULE_DESCRIPTION("GPIO-based I2C Arbitration");
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MODULE_AUTHOR("Doug Anderson <dianders@chromium.org>");
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MODULE_LICENSE("GPL v2");
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MODULE_ALIAS("platform:i2c-arb-gpio-challenge");
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