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platform/x86: Add new Dell UART backlight driver

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Dell All In One (AIO) models released after 2017 use a backlight controller
board connected to an UART.

In DSDT this uart port will be defined as:

   Name (_HID, "DELL0501")
   Name (_CID, EisaId ("PNP0501")

Instead of having a separate ACPI device with an UartSerialBusV2() resource
to model the backlight-controller, which would be the standard way to do
this.

The acpi_quirk_skip_serdev_enumeration() has special handling for this
and it will make the serial port code create a serdev controller device
for the UART instead of a /dev/ttyS0 char-dev. It will also create
a dell-uart-backlight driver platform device for this driver to bind too.

This new kernel module contains 2 drivers for this:

1. A simple platform driver which creates the actual serdev device
   (with the serdev controller device as parent)

2. A serdev driver for the created serdev device which exports
   the backlight functionality uses a standard backlight class device.

Reported-by: Roman Bogoyev <roman@computercheck.com.au>
Tested-by: Roman Bogoyev <roman@computercheck.com.au>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Co-developed-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20240513144603.93874-2-hdegoede@redhat.com
This commit is contained in:
Hans de Goede 2024-05-13 16:46:01 +02:00
parent 9426adb032
commit 484bae9e4d
3 changed files with 414 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
drivers/platform/x86/dell/Kconfig
View file

@ -145,6 +145,21 @@ config DELL_SMO8800
To compile this driver as a module, choose M here: the module will To compile this driver as a module, choose M here: the module will
be called dell-smo8800. be called dell-smo8800.
config DELL_UART_BACKLIGHT
tristate "Dell AIO UART Backlight driver"
depends on ACPI
depends on BACKLIGHT_CLASS_DEVICE
depends on SERIAL_DEV_BUS
help
Say Y here if you want to support Dell AIO UART backlight interface.
The Dell AIO machines released after 2017 come with a UART interface
to communicate with the backlight scalar board. This driver creates
a standard backlight interface and talks to the scalar board through
UART to adjust the AIO screen brightness.
To compile this driver as a module, choose M here: the module will
be called dell_uart_backlight.
config DELL_WMI config DELL_WMI
tristate "Dell WMI notifications" tristate "Dell WMI notifications"
default m default m

1
drivers/platform/x86/dell/Makefile
View file

@ -14,6 +14,7 @@ dell-smbios-objs := dell-smbios-base.o
dell-smbios-$(CONFIG_DELL_SMBIOS_WMI) += dell-smbios-wmi.o dell-smbios-$(CONFIG_DELL_SMBIOS_WMI) += dell-smbios-wmi.o
dell-smbios-$(CONFIG_DELL_SMBIOS_SMM) += dell-smbios-smm.o dell-smbios-$(CONFIG_DELL_SMBIOS_SMM) += dell-smbios-smm.o
obj-$(CONFIG_DELL_SMO8800) += dell-smo8800.o obj-$(CONFIG_DELL_SMO8800) += dell-smo8800.o
obj-$(CONFIG_DELL_UART_BACKLIGHT) += dell-uart-backlight.o
obj-$(CONFIG_DELL_WMI) += dell-wmi.o obj-$(CONFIG_DELL_WMI) += dell-wmi.o
dell-wmi-objs := dell-wmi-base.o dell-wmi-objs := dell-wmi-base.o
dell-wmi-$(CONFIG_DELL_WMI_PRIVACY) += dell-wmi-privacy.o dell-wmi-$(CONFIG_DELL_WMI_PRIVACY) += dell-wmi-privacy.o

398
drivers/platform/x86/dell/dell-uart-backlight.c Normal file
View file

@ -0,0 +1,398 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Dell AIO Serial Backlight Driver
*
* Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
* Copyright (C) 2017 AceLan Kao <acelan.kao@canonical.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/acpi.h>
#include <linux/backlight.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/serdev.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/wait.h>
#include "../serdev_helpers.h"
/* The backlight controller must respond within 1 second */
#define DELL_BL_TIMEOUT msecs_to_jiffies(1000)
#define DELL_BL_MAX_BRIGHTNESS 100
/* Defines for the commands send to the controller */
/* 1st byte Start Of Frame 3 MSB bits: cmd-len + 01010 SOF marker */
#define DELL_SOF(len) (((len) << 5) | 0x0a)
#define GET_CMD_LEN 3
#define SET_CMD_LEN 4
/* 2nd byte command */
#define CMD_GET_VERSION 0x06
#define CMD_SET_BRIGHTNESS 0x0b
#define CMD_GET_BRIGHTNESS 0x0c
#define CMD_SET_BL_POWER 0x0e
/* Indexes and other defines for response received from the controller */
#define RESP_LEN 0
#define RESP_CMD 1 /* Echo of CMD byte from command */
#define RESP_DATA 2 /* Start of received data */
#define SET_RESP_LEN 3
#define GET_RESP_LEN 4
#define MIN_RESP_LEN 3
#define MAX_RESP_LEN 80
struct dell_uart_backlight {
struct mutex mutex;
wait_queue_head_t wait_queue;
struct device *dev;
struct backlight_device *bl;
u8 *resp;
u8 resp_idx;
u8 resp_len;
u8 resp_max_len;
u8 pending_cmd;
int status;
int power;
};
/* Checksum: SUM(Length and Cmd and Data) xor 0xFF */
static u8 dell_uart_checksum(u8 *buf, int len)
{
u8 val = 0;
while (len-- > 0)
val += buf[len];
return val ^ 0xff;
}
static int dell_uart_bl_command(struct dell_uart_backlight *dell_bl,
const u8 *cmd, int cmd_len,
u8 *resp, int resp_max_len)
{
int ret;
ret = mutex_lock_killable(&dell_bl->mutex);
if (ret)
return ret;
dell_bl->status = -EBUSY;
dell_bl->resp = resp;
dell_bl->resp_idx = 0;
dell_bl->resp_len = -1; /* Invalid / unset */
dell_bl->resp_max_len = resp_max_len;
dell_bl->pending_cmd = cmd[1];
/* The TTY buffer should be big enough to take the entire cmd in one go */
ret = serdev_device_write_buf(to_serdev_device(dell_bl->dev), cmd, cmd_len);
if (ret != cmd_len) {
dev_err(dell_bl->dev, "Error writing command: %d\n", ret);
dell_bl->status = (ret < 0) ? ret : -EIO;
goto out;
}
ret = wait_event_timeout(dell_bl->wait_queue, dell_bl->status != -EBUSY,
DELL_BL_TIMEOUT);
if (ret == 0) {
dev_err(dell_bl->dev, "Timed out waiting for response.\n");
/* Clear busy status to discard bytes received after this */
dell_bl->status = -ETIMEDOUT;
}
out:
mutex_unlock(&dell_bl->mutex);
return dell_bl->status;
}
static int dell_uart_set_brightness(struct dell_uart_backlight *dell_bl, int brightness)
{
u8 set_brightness[SET_CMD_LEN], resp[SET_RESP_LEN];
set_brightness[0] = DELL_SOF(SET_CMD_LEN);
set_brightness[1] = CMD_SET_BRIGHTNESS;
set_brightness[2] = brightness;
set_brightness[3] = dell_uart_checksum(set_brightness, 3);
return dell_uart_bl_command(dell_bl, set_brightness, SET_CMD_LEN, resp, SET_RESP_LEN);
}
static int dell_uart_get_brightness(struct dell_uart_backlight *dell_bl)
{
struct device *dev = dell_bl->dev;
u8 get_brightness[GET_CMD_LEN], resp[GET_RESP_LEN];
int ret;
get_brightness[0] = DELL_SOF(GET_CMD_LEN);
get_brightness[1] = CMD_GET_BRIGHTNESS;
get_brightness[2] = dell_uart_checksum(get_brightness, 2);
ret = dell_uart_bl_command(dell_bl, get_brightness, GET_CMD_LEN, resp, GET_RESP_LEN);
if (ret)
return ret;
if (resp[RESP_LEN] != GET_RESP_LEN) {
dev_err(dev, "Unexpected get brightness response length: %d\n", resp[RESP_LEN]);
return -EIO;
}
if (resp[RESP_DATA] > DELL_BL_MAX_BRIGHTNESS) {
dev_err(dev, "Unexpected get brightness response: %d\n", resp[RESP_DATA]);
return -EIO;
}
return resp[RESP_DATA];
}
static int dell_uart_set_bl_power(struct dell_uart_backlight *dell_bl, int power)
{
u8 set_power[SET_CMD_LEN], resp[SET_RESP_LEN];
int ret;
set_power[0] = DELL_SOF(SET_CMD_LEN);
set_power[1] = CMD_SET_BL_POWER;
set_power[2] = (power == FB_BLANK_UNBLANK) ? 1 : 0;
set_power[3] = dell_uart_checksum(set_power, 3);
ret = dell_uart_bl_command(dell_bl, set_power, SET_CMD_LEN, resp, SET_RESP_LEN);
if (ret)
return ret;
dell_bl->power = power;
return 0;
}
/*
* There is no command to get backlight power status,
* so we set the backlight power to "on" while initializing,
* and then track and report its status by power variable.
*/
static int dell_uart_get_bl_power(struct dell_uart_backlight *dell_bl)
{
return dell_bl->power;
}
static int dell_uart_update_status(struct backlight_device *bd)
{
struct dell_uart_backlight *dell_bl = bl_get_data(bd);
int ret;
ret = dell_uart_set_brightness(dell_bl, bd->props.brightness);
if (ret)
return ret;
if (bd->props.power != dell_uart_get_bl_power(dell_bl))
return dell_uart_set_bl_power(dell_bl, bd->props.power);
return 0;
}
static int dell_uart_get_brightness_op(struct backlight_device *bd)
{
return dell_uart_get_brightness(bl_get_data(bd));
}
static const struct backlight_ops dell_uart_backlight_ops = {
.update_status = dell_uart_update_status,
.get_brightness = dell_uart_get_brightness_op,
};
static size_t dell_uart_bl_receive(struct serdev_device *serdev, const u8 *data, size_t len)
{
struct dell_uart_backlight *dell_bl = serdev_device_get_drvdata(serdev);
size_t i;
u8 csum;
dev_dbg(dell_bl->dev, "Recv: %*ph\n", (int)len, data);
/* Throw away unexpected bytes / remainder of response after an error */
if (dell_bl->status != -EBUSY) {
dev_warn(dell_bl->dev, "Bytes received out of band, dropping them.\n");
return len;
}
i = 0;
while (i < len && dell_bl->resp_idx != dell_bl->resp_len) {
dell_bl->resp[dell_bl->resp_idx] = data[i++];
switch (dell_bl->resp_idx) {
case RESP_LEN: /* Length byte */
dell_bl->resp_len = dell_bl->resp[RESP_LEN];
if (dell_bl->resp_len < MIN_RESP_LEN ||
dell_bl->resp_len > dell_bl->resp_max_len) {
dev_err(dell_bl->dev, "Response length %d out if range %d - %d\n",
dell_bl->resp_len, MIN_RESP_LEN, dell_bl->resp_max_len);
dell_bl->status = -EIO;
goto wakeup;
}
break;
case RESP_CMD: /* CMD byte */
if (dell_bl->resp[RESP_CMD] != dell_bl->pending_cmd) {
dev_err(dell_bl->dev, "Response cmd 0x%02x != pending 0x%02x\n",
dell_bl->resp[RESP_CMD], dell_bl->pending_cmd);
dell_bl->status = -EIO;
goto wakeup;
}
break;
}
dell_bl->resp_idx++;
}
if (dell_bl->resp_idx != dell_bl->resp_len)
return len; /* Response not complete yet */
csum = dell_uart_checksum(dell_bl->resp, dell_bl->resp_len - 1);
if (dell_bl->resp[dell_bl->resp_len - 1] == csum) {
dell_bl->status = 0; /* Success */
} else {
dev_err(dell_bl->dev, "Checksum mismatch got 0x%02x expected 0x%02x\n",
dell_bl->resp[dell_bl->resp_len - 1], csum);
dell_bl->status = -EIO;
}
wakeup:
wake_up(&dell_bl->wait_queue);
return i;
}
static const struct serdev_device_ops dell_uart_bl_serdev_ops = {
.receive_buf = dell_uart_bl_receive,
.write_wakeup = serdev_device_write_wakeup,
};
static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
{
u8 get_version[GET_CMD_LEN], resp[MAX_RESP_LEN];
struct backlight_properties props = {};
struct dell_uart_backlight *dell_bl;
struct device *dev = &serdev->dev;
int ret;
dell_bl = devm_kzalloc(dev, sizeof(*dell_bl), GFP_KERNEL);
if (!dell_bl)
return -ENOMEM;
mutex_init(&dell_bl->mutex);
init_waitqueue_head(&dell_bl->wait_queue);
dell_bl->dev = dev;
ret = devm_serdev_device_open(dev, serdev);
if (ret)
return dev_err_probe(dev, ret, "opening UART device\n");
/* 9600 bps, no flow control, these are the default but set them to be sure */
serdev_device_set_baudrate(serdev, 9600);
serdev_device_set_flow_control(serdev, false);
serdev_device_set_drvdata(serdev, dell_bl);
serdev_device_set_client_ops(serdev, &dell_uart_bl_serdev_ops);
get_version[0] = DELL_SOF(GET_CMD_LEN);
get_version[1] = CMD_GET_VERSION;
get_version[2] = dell_uart_checksum(get_version, 2);
ret = dell_uart_bl_command(dell_bl, get_version, GET_CMD_LEN, resp, MAX_RESP_LEN);
if (ret)
return dev_err_probe(dev, ret, "getting firmware version\n");
dev_dbg(dev, "Firmware version: %.*s\n", resp[RESP_LEN] - 3, resp + RESP_DATA);
/* Initialize bl_power to a known value */
ret = dell_uart_set_bl_power(dell_bl, FB_BLANK_UNBLANK);
if (ret)
return ret;
ret = dell_uart_get_brightness(dell_bl);
if (ret < 0)
return ret;
props.type = BACKLIGHT_PLATFORM;
props.brightness = ret;
props.max_brightness = DELL_BL_MAX_BRIGHTNESS;
props.power = dell_bl->power;
dell_bl->bl = devm_backlight_device_register(dev, "dell_uart_backlight",
dev, dell_bl,
&dell_uart_backlight_ops,
&props);
return PTR_ERR_OR_ZERO(dell_bl->bl);
}
struct serdev_device_driver dell_uart_bl_serdev_driver = {
.probe = dell_uart_bl_serdev_probe,
.driver = {
.name = KBUILD_MODNAME,
},
};
static int dell_uart_bl_pdev_probe(struct platform_device *pdev)
{
struct serdev_device *serdev;
struct device *ctrl_dev;
int ret;
ctrl_dev = get_serdev_controller("DELL0501", NULL, 0, "serial0");
if (IS_ERR(ctrl_dev))
return PTR_ERR(ctrl_dev);
serdev = serdev_device_alloc(to_serdev_controller(ctrl_dev));
put_device(ctrl_dev);
if (!serdev)
return -ENOMEM;
ret = serdev_device_add(serdev);
if (ret) {
dev_err(&pdev->dev, "error %d adding serdev\n", ret);
serdev_device_put(serdev);
return ret;
}
ret = serdev_device_driver_register(&dell_uart_bl_serdev_driver);
if (ret)
goto err_remove_serdev;
/*
* serdev device <-> driver matching relies on OF or ACPI matches and
* neither is available here, manually bind the driver.
*/
ret = device_driver_attach(&dell_uart_bl_serdev_driver.driver, &serdev->dev);
if (ret)
goto err_unregister_serdev_driver;
/* So that dell_uart_bl_pdev_remove() can remove the serdev */
platform_set_drvdata(pdev, serdev);
return 0;
err_unregister_serdev_driver:
serdev_device_driver_unregister(&dell_uart_bl_serdev_driver);
err_remove_serdev:
serdev_device_remove(serdev);
return ret;
}
static void dell_uart_bl_pdev_remove(struct platform_device *pdev)
{
struct serdev_device *serdev = platform_get_drvdata(pdev);
serdev_device_driver_unregister(&dell_uart_bl_serdev_driver);
serdev_device_remove(serdev);
}
static struct platform_driver dell_uart_bl_pdev_driver = {
.probe = dell_uart_bl_pdev_probe,
.remove_new = dell_uart_bl_pdev_remove,
.driver = {
.name = "dell-uart-backlight",
},
};
module_platform_driver(dell_uart_bl_pdev_driver);
MODULE_ALIAS("platform:dell-uart-backlight");
MODULE_DESCRIPTION("Dell AIO Serial Backlight driver");
MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
MODULE_LICENSE("GPL");