Re: [PATCH i-g-t v1] tests/intel/kms_pm_backlight: Add brightness-with-suspend subtest

[Karthik B S <karthik.b.s@intel.com>]

Hi Santhosh,

On 5/12/2026 4:50 PM, Santhosh Reddy Guddati wrote:
> Verify backlight brightness is preserved after suspend resume cycle,
> The test sets backlight to  a value , suspend the system and checks the
> brightness value is preserved after resume.
>
> Signed-off-by: Santhosh Reddy Guddati <santhosh.reddy.guddati@intel.com>
> ---
>   tests/intel/kms_pm_backlight.c | 26 ++++++++++++++++++++++++++
>   1 file changed, 26 insertions(+)
>
> diff --git a/tests/intel/kms_pm_backlight.c b/tests/intel/kms_pm_backlight.c
> index 58c0b4427..c2228986e 100644
> --- a/tests/intel/kms_pm_backlight.c
> +++ b/tests/intel/kms_pm_backlight.c
> @@ -65,6 +65,9 @@
>    *
>    * SUBTEST: brightness-with-dpms
>    * Description: test brightness with dpms on and off cycle.
> + *
> + * SUBTEST: brightness-with-suspend
> + * Description: Test that brightness set before suspend is preserved after resume.
>    */
>   
>   enum {
> @@ -72,6 +75,7 @@ enum {
>   	TEST_DPMS,
>   	TEST_DPMS_CYCLE,
>   	TEST_SUSPEND,
> +	TEST_SUSPEND_CYCLE,
This enum is unused, can we use TEST_NONE if we need a default enum?
>   };
>   
>   #define TOLERANCE 5 /* percent */
> @@ -188,6 +192,8 @@ static void check_dpms_cycle(igt_backlight_context_t *context)
>   {
>   	int max, val_1, val_2;
>   
> +	printf("Toggling DPMS...\n");
> +

Please remove this stray print as this is unrelated to the new test 
being added.

Regards,
Karthik.B.S
>   	igt_backlight_read(&max, "max_brightness", context);
>   	igt_assert(max);
>   
> @@ -206,6 +212,24 @@ check_suspend(igt_output_t *output)
>   	igt_system_suspend_autoresume(SUSPEND_STATE_MEM, SUSPEND_TEST_NONE);
>   }
>   
> +static void check_suspend_cycle(igt_backlight_context_t *context)
> +{
> +	int max, val1, val2;
> +
> +	igt_backlight_read(&max, "max_brightness", context);
> +	igt_assert(max);
> +
> +	igt_backlight_write(max / 2, "brightness", context);
> +	igt_backlight_read(&val1, "actual_brightness", context);
> +
> +	igt_system_suspend_autoresume(SUSPEND_STATE_MEM, SUSPEND_TEST_NONE);
> +
> +	igt_backlight_read(&val2, "actual_brightness", context);
> +	igt_assert_f(val2 == val1,
> +		     "actual_brightness after resume [%d] does not match value before suspend [%d]\n",
> +		     val2, val1);
> +}
> +
>   static void test_cleanup(igt_display_t *display, igt_backlight_context_t *context)
>   {
>   	igt_output_t *output = context->output;
> @@ -273,6 +297,8 @@ int igt_main()
>   		{ "brightness-with-dpms", "test brightness with dpms on and off cycle.",
>   		   check_dpms_cycle, TEST_DPMS_CYCLE},
>   		{ "fade-with-suspend", "test the fade with suspend.", test_fade, TEST_SUSPEND },
> +		{ "brightness-with-suspend", "test brightness is preserved after suspend/resume.",
> +		   check_suspend_cycle, TEST_SUSPEND_CYCLE },
>   	};
>   
>   	igt_fixture() {