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

[wangyuanzhi]

Hello, I have fixed compilation errors. The lenovo ThinkBook 14 G3 ACL 
notebook bios reports very small brightness value, 3 eg.

On 2023/2/27 22:20, Mario Limonciello wrote:
> 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 dark，this 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 <wangyuanzhi at 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);
>>               }
>>           }
> 
>