[PATCH v2] amdgpu: add a filter condition when set brightness

[Yuanzhi Wang]

There is a lenovo ThinkBook 14 G3 ACL notebook, when
the laptop is plugged into AC power supply, the
brightness obtained ACPI may be smaller than current
brightness.As a result the screen becomes dark，this is
not what people want. So we should add So we should
filter out very small brightness values obtained from ACPI

Signed-off-by: Yuanzhi Wang <wangyuanzhi at uniontech.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index d4196fcb85a0..20e7a178765d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -406,6 +406,7 @@ static int amdgpu_atif_handler(struct amdgpu_device *adev,
 {
 	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
 	int count;
+	int old_brightness;
 
 	DRM_DEBUG_DRIVER("event, device_class = %s, type = %#x\n",
 			event->device_class, event->type);
@@ -443,7 +444,14 @@ static int amdgpu_atif_handler(struct amdgpu_device *adev,
 				 * hardwired to post BACKLIGHT_UPDATE_SYSFS.
 				 * It probably should accept 'reason' parameter.
 				 */
-				backlight_device_set_brightness(atif->bd, req.backlight_level);
+				old_brightness = backlight_get_brightness(atif->bd);
+				if (old_brightness > req.backlight_level)
+					DRM_WARN(
+						"Old brightness %d is larger than ACPI brightness %d\n",
+						 old_brightness, req.backlight_level);
+				else
+					backlight_device_set_brightness(atif->bd,
+						 req.backlight_level);
 			}
 		}
 
-- 
2.20.1