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// 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/of.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 size_t 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 < 0 || ret < len) {
dev_err(ec_dev->dev, "Unable to write data\n");
if (ret >= 0)
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;
serdev_device_set_drvdata(serdev, ec_dev);
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;
}
/* 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);
serdev_device_set_client_ops(serdev, &cros_ec_uart_client_ops);
ret = devm_serdev_device_open(dev, serdev);
if (ret) {
dev_err(dev, "Unable to open UART device");
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);
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);
static const struct of_device_id cros_ec_uart_of_match[] = {
{ .compatible = "google,cros-ec-uart" },
{}
};
MODULE_DEVICE_TABLE(of, cros_ec_uart_of_match);
#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),
.of_match_table = cros_ec_uart_of_match,
.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>");
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