On 2/27/23 01:39, Yuanzhi Wang wrote:
When the laptop is plugged into AC or DC power supply,
the brightness obtained ACPI may be smaller than current
brightness.As a result the screen becomes darkļ¼Œthis is
not what people want.


Do you have a matching bug report with more information included?

Some relevant details I think we need:
kernel version
laptop model
BIOS version
if it's the latest BIOS
some sample numbers that this new warning/behavior catches
acpidump

At least as described this sounds like a BIOS bug.

Signed-off-by: Yuanzhi Wang <wangyuan...@uniontech.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 9 ++++++++-
  1 file changed, 8 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..93f1567028c5 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 +444,13 @@ 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 greater 
than ACPI brightness
+                                               %d\n", old_brightness, 
req.backlight_level);
+                               else
+                                       
backlight_device_set_brightness(atif->bd,
+                                               req.backlight_level);
                        }
                }

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