platform/x86: lenovo-yogabook: Add keyboard backlight control to platform driver

On the Android yb1-x90f/l models there is not ACPI method to control
the keyboard backlight brightness. Instead the second PWM controller
is exposed directly to the OS there.

Add support for controlling keyboard backlight brightness on the Android
model by using the PWM subsystem to directly control the PWM.

The Android model also requires explicitly turning the backlight off
on suspend, which on the Windows model was done automatically.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230430165807.472798-19-hdegoede@redhat.com

drivers/platform/x86/lenovo-yogabook-wmi.c

@@ -19,6 +19,7 @@
 #include <linux/leds.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pwm.h>
 #include <linux/wmi.h>
 #include <linux/workqueue.h>
 
@@ -26,6 +27,7 @@
 
 #define YB_KBD_BL_DEFAULT	128
 #define YB_KBD_BL_MAX		255
+#define YB_KBD_BL_PWM_PERIOD	13333
 
 #define YB_PDEV_NAME		"yogabook-touch-kbd-digitizer-switch"
 
@@ -48,6 +50,7 @@ struct yogabook_data {
 	struct gpio_desc *pen_touch_event;
 	struct gpio_desc *kbd_bl_led_enable;
 	struct gpio_desc *backside_hall_gpio;
+	struct pwm_device *kbd_bl_pwm;
 	int (*set_kbd_backlight)(struct yogabook_data *data, uint8_t level);
 	int pen_touch_irq;
 	int backside_hall_irq;
@@ -267,8 +270,11 @@ static int yogabook_suspend(struct device *dev)
 	struct yogabook_data *data = dev_get_drvdata(dev);
 
 	set_bit(YB_SUSPENDED, &data->flags);
-
 	flush_work(&data->work);
+
+	if (test_bit(YB_KBD_IS_ON, &data->flags))
+		data->set_kbd_backlight(data, 0);
+
 	return 0;
 }
 
@@ -423,6 +429,13 @@ static struct gpiod_lookup_table yogabook_pdev_gpios = {
 
 static int yogabook_pdev_set_kbd_backlight(struct yogabook_data *data, u8 level)
 {
+	struct pwm_state state = {
+		.period = YB_KBD_BL_PWM_PERIOD,
+		.duty_cycle = YB_KBD_BL_PWM_PERIOD * level / YB_KBD_BL_MAX,
+		.enabled = level,
+	};
+
+	pwm_apply_state(data->kbd_bl_pwm, &state);
 	gpiod_set_value(data->kbd_bl_led_enable, level ? 1 : 0);
 	return 0;
 }
@@ -472,6 +485,13 @@ static int yogabook_pdev_probe(struct platform_device *pdev)
 		goto error_put_devs;
 	}
 
+	data->kbd_bl_pwm = devm_pwm_get(dev, "pwm_soc_lpss_2");
+	if (IS_ERR(data->kbd_bl_pwm)) {
+		r = dev_err_probe(dev, PTR_ERR(data->kbd_bl_pwm),
+				  "Getting keyboard backlight PWM\n");
+		goto error_put_devs;
+	}
+
 	r = gpiod_to_irq(data->pen_touch_event);
 	if (r < 0) {
 		dev_err_probe(dev, r, "Getting pen_touch_event IRQ\n");