drm/gma500: Refactor backlight support (v2)

Refactor backlight support so that the gma_backlight_enable() /
gma_backlight_disable() / gma_backlight_set() functions used by
the Opregion handle will also work if no backlight_device gets
registered.

This is a preparation patch for not registering the gma500's own backlight
device when acpi_video should be used, since registering 2 backlight
devices for a single display really is undesirable.

Since the acpi-video interface often uses the OpRegion we need to keep
the OpRegion functional even when dev_priv->backlight_device is NULL.

As a result of this refactor the actual backlight_device_register()
call is moved to the shared backlight.c code and all #ifdefs related to
CONFIG_BACKLIGHT_CLASS_DEVICE are now also limited to backlight.c .

No functional changes intended.

This has been tested on a Packard Bell Dot SC (Intel Atom N2600, cedarview)
and a Sony Vaio vpc-x11s1e (Intel N540, poulsbo) laptop.

Changes in v2:
- Fix unused variable warnings when CONFIG_BACKLIGHT is not selected by
  marking the 2 variables as  __maybe_unused.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220917205920.647212-2-hdegoede@redhat.com

1 files changed, 5 insertions, 60 deletions

diff --git a/drivers/gpu/drm/gma500/oaktrail_device.c b/drivers/gpu/drm/gma500/oaktrail_device.c
index f90e628cb482..2531959d3d77 100644
--- a/drivers/gpu/drm/gma500/oaktrail_device.c
+++ b/drivers/gpu/drm/gma500/oaktrail_device.c
@@ -5,7 +5,6 @@
  *
  **************************************************************************/
 
-#include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/module.h>
@@ -37,29 +36,18 @@ static int oaktrail_output_init(struct drm_device *dev)
  *	Provide the low level interfaces for the Moorestown backlight
  */
 
-#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE
-
 #define MRST_BLC_MAX_PWM_REG_FREQ	    0xFFFF
 #define BLC_PWM_PRECISION_FACTOR 100	/* 10000000 */
 #define BLC_PWM_FREQ_CALC_CONSTANT 32
 #define MHz 1000000
 #define BLC_ADJUSTMENT_MAX 100
 
-static struct backlight_device *oaktrail_backlight_device;
-static int oaktrail_brightness;
-
-static int oaktrail_set_brightness(struct backlight_device *bd)
+static void oaktrail_set_brightness(struct drm_device *dev, int level)
 {
-	struct drm_device *dev = bl_get_data(oaktrail_backlight_device);
 	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
-	int level = bd->props.brightness;
 	u32 blc_pwm_ctl;
 	u32 max_pwm_blc;
 
-	/* Percentage 1-100% being valid */
-	if (level < 1)
-		level = 1;
-
 	if (gma_power_begin(dev, 0)) {
 		/* Calculate and set the brightness value */
 		max_pwm_blc = REG_READ(BLC_PWM_CTL) >> 16;
@@ -82,19 +70,9 @@ static int oaktrail_set_brightness(struct backlight_device *bd)
 		REG_WRITE(BLC_PWM_CTL, (max_pwm_blc << 16) | blc_pwm_ctl);
 		gma_power_end(dev);
 	}
-	oaktrail_brightness = level;
-	return 0;
-}
-
-static int oaktrail_get_brightness(struct backlight_device *bd)
-{
-	/* return locally cached var instead of HW read (due to DPST etc.) */
-	/* FIXME: ideally return actual value in case firmware fiddled with
-	   it */
-	return oaktrail_brightness;
 }
 
-static int device_backlight_init(struct drm_device *dev)
+static int oaktrail_backlight_init(struct drm_device *dev)
 {
 	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
 	unsigned long core_clock;
@@ -123,44 +101,11 @@ static int device_backlight_init(struct drm_device *dev)
 		REG_WRITE(BLC_PWM_CTL, value | (value << 16));
 		gma_power_end(dev);
 	}
-	return 0;
-}
-
-static const struct backlight_ops oaktrail_ops = {
-	.get_brightness = oaktrail_get_brightness,
-	.update_status  = oaktrail_set_brightness,
-};
 
-static int oaktrail_backlight_init(struct drm_device *dev)
-{
-	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
-	int ret;
-	struct backlight_properties props;
-
-	memset(&props, 0, sizeof(struct backlight_properties));
-	props.max_brightness = 100;
-	props.type = BACKLIGHT_PLATFORM;
-
-	oaktrail_backlight_device = backlight_device_register("oaktrail-bl",
-				NULL, (void *)dev, &oaktrail_ops, &props);
-
-	if (IS_ERR(oaktrail_backlight_device))
-		return PTR_ERR(oaktrail_backlight_device);
-
-	ret = device_backlight_init(dev);
-	if (ret < 0) {
-		backlight_device_unregister(oaktrail_backlight_device);
-		return ret;
-	}
-	oaktrail_backlight_device->props.brightness = 100;
-	oaktrail_backlight_device->props.max_brightness = 100;
-	backlight_update_status(oaktrail_backlight_device);
-	dev_priv->backlight_device = oaktrail_backlight_device;
+	oaktrail_set_brightness(dev, PSB_MAX_BRIGHTNESS);
 	return 0;
 }
 
-#endif
-
 /*
  *	Provide the Moorestown specific chip logic and low level methods
  *	for power management
@@ -545,9 +490,9 @@ const struct psb_ops oaktrail_chip_ops = {
 
 	.output_init = oaktrail_output_init,
 
-#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE
 	.backlight_init = oaktrail_backlight_init,
-#endif
+	.backlight_set = oaktrail_set_brightness,
+	.backlight_name = "oaktrail-bl",
 
 	.save_regs = oaktrail_save_display_registers,
 	.restore_regs = oaktrail_restore_display_registers,