@@ -4985,6 +4985,13 @@ S: Maintained
F: Documentation/devicetree/bindings/sound/google,cros-ec-codec.yaml
F: sound/soc/codecs/cros_ec_codec.*
+CHROMEOS EC UART DRIVER
+M: Bhanu Prakash Maiya <bhanumaiya@chromium.org>
+R: Benson Leung <bleung@chromium.org>
+R: Tzung-Bi Shih <tzungbi@kernel.org>
+S: Maintained
+F: drivers/platform/chrome/cros_ec_uart.c
+
CHROMEOS EC SUBDRIVERS
M: Benson Leung <bleung@chromium.org>
R: Guenter Roeck <groeck@chromium.org>
@@ -119,6 +119,16 @@ config CROS_EC_SPI
response time cannot be guaranteed, we support ignoring
'pre-amble' bytes before the response actually starts.
+config CROS_EC_UART
+ tristate "ChromeOS Embedded Controller (UART)"
+ depends on CROS_EC && ACPI && SERIAL_DEV_BUS
+ help
+ If you say Y here, you get support for talking to the ChromeOS EC
+ through a UART, using a byte-level protocol.
+
+ To compile this driver as a module, choose M here: the
+ module will be called cros_ec_uart.
+
config CROS_EC_LPC
tristate "ChromeOS Embedded Controller (LPC)"
depends on CROS_EC && ACPI && (X86 || COMPILE_TEST)
@@ -15,6 +15,7 @@ obj-$(CONFIG_CROS_EC_ISHTP) += cros_ec_ishtp.o
obj-$(CONFIG_CROS_TYPEC_SWITCH) += cros_typec_switch.o
obj-$(CONFIG_CROS_EC_RPMSG) += cros_ec_rpmsg.o
obj-$(CONFIG_CROS_EC_SPI) += cros_ec_spi.o
+obj-$(CONFIG_CROS_EC_UART) += cros_ec_uart.o
cros_ec_lpcs-objs := cros_ec_lpc.o cros_ec_lpc_mec.o
obj-$(CONFIG_CROS_EC_TYPEC) += cros_ec_typec.o
obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpcs.o
new file mode 100644
@@ -0,0 +1,352 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * UART interface for ChromeOS Embedded Controller
+ *
+ * Copyright 2020-2022 Google LLC.
+ */
+
+#include <linux/acpi.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/serdev.h>
+#include <linux/slab.h>
+#include <uapi/linux/sched/types.h>
+
+#include "cros_ec.h"
+
+/*
+ * EC sends contiguous bytes of response packet on UART AP RX.
+ * TTY driver in AP accumulates incoming bytes and calls the registered callback
+ * function. Byte count can range from 1 to MAX bytes supported by EC.
+ * This driver should wait for long time for all callbacks to be processed.
+ * Considering the worst case scenario, wait for 500 msec. This timeout should
+ * account for max latency and some additional guard time.
+ * Best case: Entire packet is received in ~200 ms, wait queue will be released
+ * and packet will be processed.
+ * Worst case: TTY driver sends bytes in multiple callbacks. In this case this
+ * driver will wait for ~1 sec beyond which it will timeout.
+ * This timeout value should not exceed ~500 msec because in case if
+ * EC_CMD_REBOOT_EC sent, high level driver should be able to intercept EC
+ * in RO.
+ */
+#define EC_MSG_DEADLINE_MS 500
+
+/**
+ * struct response_info - Encapsulate EC response related
+ * information for passing between function
+ * cros_ec_uart_pkt_xfer() and cros_ec_uart_rx_bytes()
+ * callback.
+ * @data: Copy the data received from EC here.
+ * @max_size: Max size allocated for the @data buffer. If the
+ * received data exceeds this value, we log an error.
+ * @size: Actual size of data received from EC. This is also
+ * used to accumulate byte count with response is received
+ * in dma chunks.
+ * @exp_len: Expected bytes of response from EC including header.
+ * @status: Re-init to 0 before sending a cmd. Updated to 1 when
+ * a response is successfully received, or an error number
+ * on failure.
+ * @wait_queue: Wait queue EC response where the cros_ec sends request
+ * to EC and waits
+ */
+struct response_info {
+ void *data;
+ size_t max_size;
+ size_t size;
+ size_t exp_len;
+ int status;
+ wait_queue_head_t wait_queue;
+};
+
+/**
+ * struct cros_ec_uart - information about a uart-connected EC
+ *
+ * @serdev: serdev uart device we are connected to.
+ * @baudrate: UART baudrate of attached EC device.
+ * @flowcontrol: UART flowcontrol of attached device.
+ * @irq: Linux IRQ number of associated serial device.
+ * @response: Response info passing between cros_ec_uart_pkt_xfer()
+ * and cros_ec_uart_rx_bytes()
+ */
+struct cros_ec_uart {
+ struct serdev_device *serdev;
+ u32 baudrate;
+ u8 flowcontrol;
+ u32 irq;
+ struct response_info response;
+};
+
+static int cros_ec_uart_rx_bytes(struct serdev_device *serdev,
+ const u8 *data,
+ size_t count)
+{
+ struct ec_host_response *host_response;
+ struct cros_ec_device *ec_dev = serdev_device_get_drvdata(serdev);
+ struct cros_ec_uart *ec_uart = ec_dev->priv;
+ struct response_info *resp = &ec_uart->response;
+
+ /* Check if bytes were sent out of band */
+ if (!resp->data) {
+ /* Discard all bytes */
+ dev_warn(ec_dev->dev, "Bytes received out of band, dropping them.\n");
+ return count;
+ }
+
+ /*
+ * Check if incoming bytes + resp->size is greater than allocated
+ * buffer in din by cros_ec. This will ensure that if EC sends more
+ * bytes than max_size, waiting process will be notified with an error.
+ */
+ if (resp->size + count > resp->max_size) {
+ resp->status = -EMSGSIZE;
+ wake_up(&resp->wait_queue);
+ return count;
+ }
+
+ memcpy(resp->data + resp->size, data, count);
+
+ resp->size += count;
+
+ /* Read data_len if we received response header and if exp_len was not read before. */
+ if (resp->size >= sizeof(*host_response) && resp->exp_len == 0) {
+ host_response = (struct ec_host_response *)resp->data;
+ resp->exp_len = host_response->data_len + sizeof(*host_response);
+ }
+
+ /* If driver received response header and payload from EC, wake up the wait queue. */
+ if (resp->size >= sizeof(*host_response) && resp->size == resp->exp_len) {
+ resp->status = 1;
+ wake_up(&resp->wait_queue);
+ }
+
+ return count;
+}
+
+static int cros_ec_uart_pkt_xfer(struct cros_ec_device *ec_dev,
+ struct cros_ec_command *ec_msg)
+{
+ struct cros_ec_uart *ec_uart = ec_dev->priv;
+ struct serdev_device *serdev = ec_uart->serdev;
+ struct response_info *resp = &ec_uart->response;
+ struct ec_host_response *host_response;
+ unsigned int len;
+ int ret, i;
+ u8 sum;
+
+ len = cros_ec_prepare_tx(ec_dev, ec_msg);
+ dev_dbg(ec_dev->dev, "Prepared len=%d\n", len);
+
+ /* Setup for incoming response */
+ resp->data = ec_dev->din;
+ resp->max_size = ec_dev->din_size;
+ resp->size = 0;
+ resp->exp_len = 0;
+ resp->status = 0;
+
+ ret = serdev_device_write_buf(serdev, ec_dev->dout, len);
+ if (ret < len) {
+ dev_err(ec_dev->dev, "Unable to write data\n");
+ ret = -EIO;
+ goto exit;
+ }
+
+ ret = wait_event_timeout(resp->wait_queue, resp->status,
+ msecs_to_jiffies(EC_MSG_DEADLINE_MS));
+ if (ret == 0) {
+ dev_warn(ec_dev->dev, "Timed out waiting for response.\n");
+ ret = -ETIMEDOUT;
+ goto exit;
+ }
+
+ if (resp->status < 0) {
+ ret = resp->status;
+ dev_warn(ec_dev->dev, "Error response received: %d\n", ret);
+ goto exit;
+ }
+
+ host_response = (struct ec_host_response *)ec_dev->din;
+ ec_msg->result = host_response->result;
+
+ if (host_response->data_len > ec_msg->insize) {
+ dev_err(ec_dev->dev, "Resp too long (%d bytes, expected %d)\n",
+ host_response->data_len, ec_msg->insize);
+ ret = -ENOSPC;
+ goto exit;
+ }
+
+ /* Validate checksum */
+ sum = 0;
+ for (i = 0; i < sizeof(*host_response) + host_response->data_len; i++)
+ sum += ec_dev->din[i];
+
+ if (sum) {
+ dev_err(ec_dev->dev, "Bad packet checksum calculated %x\n", sum);
+ ret = -EBADMSG;
+ goto exit;
+ }
+
+ memcpy(ec_msg->data, ec_dev->din + sizeof(*host_response), host_response->data_len);
+
+ ret = host_response->data_len;
+
+exit:
+ /* Invalidate response buffer to guard against out of band rx data */
+ resp->data = NULL;
+
+ if (ec_msg->command == EC_CMD_REBOOT_EC)
+ msleep(EC_REBOOT_DELAY_MS);
+
+ return ret;
+}
+
+static int cros_ec_uart_resource(struct acpi_resource *ares, void *data)
+{
+ struct cros_ec_uart *ec_uart = data;
+ struct acpi_resource_uart_serialbus *sb = &ares->data.uart_serial_bus;
+
+ if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS &&
+ sb->type == ACPI_RESOURCE_SERIAL_TYPE_UART) {
+ ec_uart->baudrate = sb->default_baud_rate;
+ dev_dbg(&ec_uart->serdev->dev, "Baudrate %d\n", ec_uart->baudrate);
+
+ ec_uart->flowcontrol = sb->flow_control;
+ dev_dbg(&ec_uart->serdev->dev, "Flow control %d\n", ec_uart->flowcontrol);
+ }
+
+ return 0;
+}
+
+static int cros_ec_uart_acpi_probe(struct cros_ec_uart *ec_uart)
+{
+ int ret;
+ LIST_HEAD(resources);
+ struct acpi_device *adev = ACPI_COMPANION(&ec_uart->serdev->dev);
+
+ ret = acpi_dev_get_resources(adev, &resources, cros_ec_uart_resource, ec_uart);
+ if (ret < 0)
+ return ret;
+
+ acpi_dev_free_resource_list(&resources);
+
+ /* Retrieve GpioInt and translate it to Linux IRQ number */
+ ret = acpi_dev_gpio_irq_get(adev, 0);
+ if (ret < 0)
+ return ret;
+
+ ec_uart->irq = ret;
+ dev_dbg(&ec_uart->serdev->dev, "IRQ number %d\n", ec_uart->irq);
+
+ return 0;
+}
+
+static const struct serdev_device_ops cros_ec_uart_client_ops = {
+ .receive_buf = cros_ec_uart_rx_bytes,
+};
+
+static int cros_ec_uart_probe(struct serdev_device *serdev)
+{
+ struct device *dev = &serdev->dev;
+ struct cros_ec_device *ec_dev;
+ struct cros_ec_uart *ec_uart;
+ int ret;
+
+ ec_uart = devm_kzalloc(dev, sizeof(*ec_uart), GFP_KERNEL);
+ if (!ec_uart)
+ return -ENOMEM;
+
+ ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
+ if (!ec_dev)
+ return -ENOMEM;
+
+ ret = devm_serdev_device_open(dev, serdev);
+ if (ret) {
+ dev_err(dev, "Unable to open UART device");
+ return ret;
+ }
+
+ serdev_device_set_drvdata(serdev, ec_dev);
+ serdev_device_set_client_ops(serdev, &cros_ec_uart_client_ops);
+ init_waitqueue_head(&ec_uart->response.wait_queue);
+
+ ec_uart->serdev = serdev;
+
+ ret = cros_ec_uart_acpi_probe(ec_uart);
+ if (ret < 0) {
+ dev_err(dev, "Failed to get ACPI info (%d)", ret);
+ return ret;
+ }
+
+ ret = serdev_device_set_baudrate(serdev, ec_uart->baudrate);
+ if (ret < 0) {
+ dev_err(dev, "Failed to set up host baud rate (%d)", ret);
+ return ret;
+ }
+
+ serdev_device_set_flow_control(serdev, ec_uart->flowcontrol);
+
+ /* Initialize ec_dev for cros_ec */
+ ec_dev->phys_name = dev_name(dev);
+ ec_dev->dev = dev;
+ ec_dev->priv = ec_uart;
+ ec_dev->irq = ec_uart->irq;
+ ec_dev->cmd_xfer = NULL;
+ ec_dev->pkt_xfer = cros_ec_uart_pkt_xfer;
+ ec_dev->din_size = sizeof(struct ec_host_response) +
+ sizeof(struct ec_response_get_protocol_info);
+ ec_dev->dout_size = sizeof(struct ec_host_request);
+
+ return cros_ec_register(ec_dev);
+}
+
+static void cros_ec_uart_remove(struct serdev_device *serdev)
+{
+ struct cros_ec_device *ec_dev = serdev_device_get_drvdata(serdev);
+
+ cros_ec_unregister(ec_dev);
+};
+
+static int __maybe_unused cros_ec_uart_suspend(struct device *dev)
+{
+ struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
+
+ return cros_ec_suspend(ec_dev);
+}
+
+static int __maybe_unused cros_ec_uart_resume(struct device *dev)
+{
+ struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
+
+ return cros_ec_resume(ec_dev);
+}
+
+static SIMPLE_DEV_PM_OPS(cros_ec_uart_pm_ops, cros_ec_uart_suspend,
+ cros_ec_uart_resume);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id cros_ec_uart_acpi_id[] = {
+ { "GOOG0019", 0 },
+ {}
+};
+
+MODULE_DEVICE_TABLE(acpi, cros_ec_uart_acpi_id);
+#endif
+
+static struct serdev_device_driver cros_ec_uart_driver = {
+ .driver = {
+ .name = "cros-ec-uart",
+ .acpi_match_table = ACPI_PTR(cros_ec_uart_acpi_id),
+ .pm = &cros_ec_uart_pm_ops,
+ },
+ .probe = cros_ec_uart_probe,
+ .remove = cros_ec_uart_remove,
+};
+
+module_serdev_device_driver(cros_ec_uart_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("UART interface for ChromeOS Embedded Controller");
+MODULE_AUTHOR("Bhanu Prakash Maiya <bhanumaiya@chromium.org>");