Re: [PATCH i-g-t] tests/kms_bw: Allow custom modes for external panels

["Joshi, Kunal1" <kunal1.joshi@intel.com>]

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Hello Karthik,

On 07-04-2026 15:22, Karthik B S wrote:
> Currently the test is rejecting all the outputs where the mode is not
> matching. This is leading to excessive skips on configs wherer the tests
> were passing previouly.
>
> Instead of this, use default mode for fixed mode panels if the required
> custom mode is not found. And use custom mode for external panels as
> these are allowed and have also been passing previously.
>
> Cc: Jason-JH Lin<jason-jh.lin@mediatek.com>
> Cc: Kunal Joshi<kunal1.joshi@intel.com>
> Signed-off-by: Karthik B S<karthik.b.s@intel.com>
> ---
>   tests/kms_bw.c | 57 ++++++++++++++++++++++++++++++++------------------
>   1 file changed, 37 insertions(+), 20 deletions(-)
>
> diff --git a/tests/kms_bw.c b/tests/kms_bw.c
> index 4df5c2cee..4a32ec811 100644
> --- a/tests/kms_bw.c
> +++ b/tests/kms_bw.c
> @@ -186,14 +186,16 @@ static void force_output_mode(data_t *d, igt_output_t *output,
>   	igt_output_override_mode(output, mode);
>   }
>   
> -static bool output_mode_supported(igt_output_t *output, const drmModeModeInfo *mode)
> +/* Check if output has a matching mode and call it out if mode is being forced */
> +static void output_mode_supported(igt_output_t *output, const drmModeModeInfo *mode)
Since the function is now void and purely informational, the name
output_mode_supported no longer reflects what it does. Consider renaming
>   {
>   	drmModeConnector *connector = output->config.connector;
> +	drmModeModeInfo *default_mode;
>   	int i;
>   
>   	/* Virtual/forced sinks support all modes */
>   	if (!igt_output_is_connected(output))
> -		return true;
> +		return;
>   
>   	for (i = 0; i < connector->count_modes; i++) {
>   		drmModeModeInfo *conn_mode = &connector->modes[i];
> @@ -204,26 +206,32 @@ static bool output_mode_supported(igt_output_t *output, const drmModeModeInfo *m
>   			igt_debug("Found matching mode for %dx%d@%dHz on %s\n",
>   				  mode->hdisplay, mode->vdisplay, mode->vrefresh,
>   				  igt_output_name(output));
> -			return true;
>   		}
>   	}
>   
> -	igt_info("Mode %dx%d@%dHz not supported by %s (has %d modes)\n",
> -		 mode->hdisplay, mode->vdisplay, mode->vrefresh,
> -		 igt_output_name(output), connector->count_modes);
> -
> -	return false;
> +	if (output_is_internal_panel(output)) {
> +		default_mode = igt_output_get_mode(output);
> +		igt_info("Mode %dx%d@%dHz not supported by %s (has %d modes).\n"
> +			 "%s Default mode: %dx%d@%dHz\n",
> +			 mode->hdisplay, mode->vdisplay, mode->vrefresh,
> +			 igt_output_name(output), connector->count_modes, igt_output_name(output),
> +			 default_mode->hdisplay, default_mode->vdisplay, default_mode->vrefresh);
> +	} else {
> +		igt_info("Mode %dx%d@%dHz not supported by %s (has %d modes). Forcing mode.\n",
> +			 mode->hdisplay, mode->vdisplay, mode->vrefresh,
> +			 igt_output_name(output), connector->count_modes);
> +	}
Previously the matching case returned immediately from inside the loop.
If that early return is removed without adding equivalent control flow,
then when a matching mode /is/found the function will still fall through
and print the "not supported" message afterward. In that case we would end
up logging both "Found matching mode" and "not supported" for the same
connector/mode pair.
>   }
>   
>   static void run_test_linear_tiling(data_t *data, int n_crtcs, const drmModeModeInfo *mode, bool physical) {
>   	igt_display_t *display = &data->display;
>   	igt_output_t *output;
> +	drmModeModeInfo fb_mode;
>   	struct igt_fb buffer[IGT_MAX_PIPES];
>   	igt_crc_t zero, captured[IGT_MAX_PIPES];
>   	int i = 0, num_pipes = 0;
>   	igt_crtc_t *crtc;
>   	int ret;
> -	bool has_supported_mode = false;
>   
>   	/* Cannot use igt_display_n_crtcs() due to fused pipes on i915 where they do
>   	 * not give the numver of valid crtcs and always return IGT_MAX_PIPES */
> @@ -242,14 +250,26 @@ static void run_test_linear_tiling(data_t *data, int n_crtcs, const drmModeModeI
>   		crtc = data->crtc[i];
>   
>   		output = physical ? data->connected_output[i] : data->output[i];
> -		if (!output || !output_mode_supported(output, mode)) {
> +		if (!output)
>   			continue;
> -		}
>   
> -		force_output_mode(data, output, mode);
> +		output_mode_supported(output, mode);
> +
> +		/*
> +		 * On fixed mode panels trying to force a custom mode can lead to failures or
> +		 * implicit handling where the default mode is used even though custom mode is requested.
> +		 * To avoid this use default mode on fixed mode panels and
> +		 * use custom modes only on external panels.
> +		 */
> +		if (output_is_internal_panel(output)) {
> +			fb_mode = *igt_output_get_mode(output);
> +		} else {
> +			force_output_mode(data, output, mode);
> +			fb_mode = *mode;
> +		}
For internal panels, the subtest will always run at the panel's native mode
regardless of what mode the subtest requested. So a subtest meant to stress
e.g. 4K@60 bandwidth will actually run at whatever the native eDP resolution
is. The test will pass but it won't be validating the bandwidth scenario the
subtest name implies.

For internal panels where the requested custom mode is not natively 
supported,
instead of silently falling back to the default mode, skip that output 
for that
specific subtest (also prefer external panel first to reduce skip's),
since the bandwidth scenario cannot actually be exercised on that panel.

I know we are doing this so we eventually have less skip's, but someone 
who won't
know this fact may have false sense of coverage (i.e we tested 4x4k).

Other alternative would be changing test description to state test 
exercise's standard
modes on external panel with default mode internal if present. This 
scenario is more likely as user will
have internal panel running along with some external display's connected.

Thanks and Regards
Kunal Joshi
>   
> -		igt_create_color_fb(display->drm_fd, mode->hdisplay,
> -				    mode->vdisplay, DRM_FORMAT_XRGB8888,
> +		igt_create_color_fb(display->drm_fd, fb_mode.hdisplay,
> +				    fb_mode.vdisplay, DRM_FORMAT_XRGB8888,
>   				    DRM_FORMAT_MOD_LINEAR, 1.f, 0.f, 0.f,
>   				    &buffer[i]);
>   
> @@ -258,10 +278,8 @@ static void run_test_linear_tiling(data_t *data, int n_crtcs, const drmModeModeI
>   		igt_plane_set_fb(data->primary[i], &buffer[i]);
>   		igt_info("Assigning pipe %s to output %s with mode %s\n",
>   			 igt_crtc_name(crtc), igt_output_name(output),
> -			 mode->name);
> -		has_supported_mode = true;
> +			 fb_mode.name);
>   	}
> -	igt_skip_on_f(!has_supported_mode, "Unsupported mode for all pipes\n");
>   
>   	ret = igt_display_try_commit_atomic(display,
>   					    DRM_MODE_ATOMIC_ALLOW_MODESET |
> @@ -273,9 +291,8 @@ static void run_test_linear_tiling(data_t *data, int n_crtcs, const drmModeModeI
>   
>   	for (i = 0; i < n_crtcs; i++) {
>   		output = physical ? data->connected_output[i] : data->output[i];
> -		if (!output || !output_mode_supported(output, mode)) {
> +		if (!output)
>   			continue;
> -		}
>   
>   		igt_pipe_crc_collect_crc(data->pipe_crc[i], &captured[i]);
>   		igt_assert_f(!igt_check_crc_equal(&zero, &captured[i]),
> @@ -284,7 +301,7 @@ static void run_test_linear_tiling(data_t *data, int n_crtcs, const drmModeModeI
>   
>   	for (i = n_crtcs - 1; i >= 0; i--) {
>   		output = physical ? data->connected_output[i] : data->output[i];
> -		if (!output || !output_mode_supported(output, mode))
> +		if (!output)
>   			continue;
>   
>   		igt_remove_fb(display->drm_fd, &buffer[i]);

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