Re: [PATCH i-g-t v2] tests/intel/kms_pm_backlight: Setup output before reading writing backlight

["Naladala, Ramanaidu" <Ramanaidu.naladala@intel.com>]

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Hi Suraj,

On 4/7/2026 1:47 PM, Karthik B S wrote:
> Hi Suraj,
>
> On 4/7/2026 11:13 AM, Suraj Kandpal wrote:
>> Currently many pm backlight tests assume that panel will stay up until
>> unless we tell it to go down or AUX transactions are happening.
>> That is not the case, some panels when they detect that there are no
>> changes or commits going in, it will go to a lower power state. This
>> causes issue in this test like AUX suddenly timing out (mostly in
>> fade tests where each backlight change has a 10ms sleep and many
>> steps giving panel to internally go in low power state). Also since
>> changing backlight has its own interface it does not count as a commit
>> hence does not contribute to the panel staying on.
>> Also trying to change a backlight when panel is not up does not make sense.
>> To solve this setup the output and do a flip to make sure panel is not
>> down to simulate a real life use case on when backlight is changed.
>>
>> Signed-off-by: Suraj Kandpal<suraj.kandpal@intel.com>
>> Reviewed-by: Karthik B S<karthik.b.s@intel.com>
>> ---
>> v1 -> v2:
>> - Remove setup and commit function from check dpms as it is not
>> needed there (Karthik)
>>
>>    tests/intel/kms_pm_backlight.c | 20 ++++++++++++++++++++
>>    1 file changed, 20 insertions(+)
>>
>> diff --git a/tests/intel/kms_pm_backlight.c b/tests/intel/kms_pm_backlight.c
>> index daa70c716..f108e8387 100644
>> --- a/tests/intel/kms_pm_backlight.c
>> +++ b/tests/intel/kms_pm_backlight.c
>> @@ -84,6 +84,24 @@ enum {
>>    
>>    IGT_TEST_DESCRIPTION("Basic backlight sysfs test");
>>    
>> +static void setup_output_and_commit(igt_backlight_context_t *context)
>> +{
>> +	igt_output_t *output = context->output;
>> +	igt_display_t *display = output->display;
>> +	drmModeModeInfo *mode;
>> +	igt_plane_t *primary;
>> +	struct igt_fb fb;
>> +
>> +	mode = igt_output_get_mode(output);
>> +	igt_create_pattern_fb(display->drm_fd,
>> +			      mode->hdisplay, mode->vdisplay,
>> +			      DRM_FORMAT_XRGB8888,
>> +			      DRM_FORMAT_MOD_LINEAR, &fb);
>> +	primary = igt_output_get_plane_type(output, DRM_PLANE_TYPE_PRIMARY);
>> +	igt_plane_set_fb(primary, &fb);
>> +	igt_display_commit2(display, display->is_atomic ? COMMIT_ATOMIC : COMMIT_LEGACY);
>> +}
>> +
Ensure the framebuffer is destroyed once it is no longer needed.

Thanks,
Ramanaidu N.
> Sorry missed this part on rev1. Instead of creating fb's everytime we
> could just create two fbs and toggle b/n them. Also remove the fb after
> the test.
>
> Regards,
> Karthik.B.S
>>    static void test_and_verify(igt_backlight_context_t *context, int val)
>>    {
>>    	const int tolerance = val * TOLERANCE / 100;
>> @@ -133,10 +151,12 @@ static void test_fade(igt_backlight_context_t *context)
>>    
>>    	/* Fade out, then in */
>>    	for (i = context->max; i > 0; i -= context->max / FADESTEPS) {
>> +		setup_output_and_commit(context);
>>    		test_and_verify(context, i);
>>    		nanosleep(&ts, NULL);
>>    	}
>>    	for (i = 0; i <= context->max; i += context->max / FADESTEPS) {
>> +		setup_output_and_commit(context);
>>    		test_and_verify(context, i);
>>    		nanosleep(&ts, NULL);
>>    	}

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