Re: [igt-dev] [PATCH i-g-t] tests/kms_concurrent: Test maximum number of planes supported by the platform

["Kahola, Mika" <mika.kahola@intel.com>]

-----Original Message-----
From: Lisovskiy, Stanislav <stanislav.lisovskiy@intel.com> 
Sent: Thursday, March 26, 2020 10:04 AM
To: Kahola, Mika <mika.kahola@intel.com>
Cc: igt-dev@lists.freedesktop.org; juhapekka.heikkla@gmail.com
Subject: Re: [igt-dev] [PATCH i-g-t] tests/kms_concurrent: Test maximum number of planes supported by the platform

On Thu, Mar 26, 2020 at 09:09:28AM +0200, Mika Kahola wrote:
> There was an error in commit 0ab05a51a059 on computing number of 
> maximum supported planes. This patch proposes a fix to this commit by 
> first computing the number of planes that are within platform's 
> bandwidth requirements, resets the display and then executes the actual testing.
> 
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> ---
>  tests/kms_concurrent.c | 104 
> +++++++++++++++++++----------------------
>  1 file changed, 47 insertions(+), 57 deletions(-)
> 
> diff --git a/tests/kms_concurrent.c b/tests/kms_concurrent.c index 
> 61137139..98a115da 100644
> --- a/tests/kms_concurrent.c
> +++ b/tests/kms_concurrent.c
> @@ -195,6 +195,27 @@ prepare_planes(data_t *data, enum pipe pipe, int max_planes,
>  	igt_plane_set_fb(data->plane[primary->index], 
> &data->fb[primary->index]);  }
>  
> +static int test_bandwidth(data_t *data, enum pipe pipe, igt_output_t 
> +*output) {
> +
> +	int n_planes = data->display.pipes[pipe].n_planes;
> +	int max_planes;
> +	int i;
> +	int ret;
> +
> +	igt_pipe_refresh(&data->display, pipe, true);
> +
> +	for (i = 1; i <= n_planes; i++) {
> +		prepare_planes(data, pipe, i, output);
> +		ret = igt_display_try_commit2(&data->display, COMMIT_ATOMIC | DRM_MODE_ATOMIC_TEST_ONLY);
> +		if (ret != 0)
> +			break;          => this will leave max_planes ununitialized if commit fails for i==1
> +		max_planes = i;
> +	}
> +
> +	return max_planes;
> +}

This code might return uninitialized max_planes. For example you start cycle, igt_display_commit2 returns non-zero, then you break, but max_planes is left uninitialized and then garbage is returned. 

You actually don't even need max_planes variable - could just return i - 1, thus avoiding unnecessary assignments or otherwise should initialize max_planes with 0.

Stan

You're propably right. One shouldn't take granted that variable is initialized as 0. Actually, that wouldn't make any sense either. I'll go by returning i-1 as you proposed. 

Thanks for the review!

Cheers,
Mika
> +
>  static void
>  test_plane_position_with_output(data_t *data, enum pipe pipe, int max_planes,
>  				igt_output_t *output)
> @@ -208,7 +229,7 @@ test_plane_position_with_output(data_t *data, enum pipe pipe, int max_planes,
>  	i = 0;
>  	while (i < iterations || loop_forever) {
>  		prepare_planes(data, pipe, max_planes, output);
> -		igt_display_try_commit2(&data->display, COMMIT_ATOMIC);
> +		igt_display_commit2(&data->display, COMMIT_ATOMIC);
>  		i++;
>  	}
>  }
> @@ -241,44 +262,17 @@ get_lowres_mode(data_t *data, const drmModeModeInfo *mode_default,
>  	return mode;
>  }
>  
> -static int
> +static void
>  test_resolution_with_output(data_t *data, enum pipe pipe, 
> igt_output_t *output)  {
>  	const drmModeModeInfo *mode_hi, *mode_lo;
>  	int iterations = opt.iterations < 1 ? 1 : opt.iterations;
>  	bool loop_forever = opt.iterations == LOOP_FOREVER ? true : false;
> -	int i, c, ret;
> -	int max_planes = data->display.pipes[pipe].n_planes;
> -	igt_plane_t *primary;
> -	drmModeModeInfo *mode;
> +	int i;
>  
>  	i = 0;
>  	while (i < iterations || loop_forever) {
>  		igt_output_set_pipe(output, pipe);
> -		for (c = 0; c < max_planes; c++) {
> -			igt_plane_t *plane = igt_output_get_plane(output, c);
> -
> -			if (plane->type != DRM_PLANE_TYPE_PRIMARY)
> -				continue;
> -			primary = igt_output_get_plane_type(output, DRM_PLANE_TYPE_PRIMARY);
> -			data->plane[primary->index] = primary;
> -			mode = igt_output_get_mode(output);
> -			igt_create_color_fb(data->drm_fd, mode->hdisplay, mode->vdisplay,
> -						DRM_FORMAT_XRGB8888,
> -						LOCAL_I915_FORMAT_MOD_X_TILED,
> -						0.0f, 0.0f, 1.0f,
> -						&data->fb[primary->index]);
> -			igt_plane_set_fb(data->plane[primary->index], &data->fb[primary->index]);
> -			ret = igt_display_try_commit2(&data->display, COMMIT_ATOMIC);
> -			if (ret) {
> -				igt_plane_set_fb(data->plane[i], NULL);
> -				igt_remove_fb(data->drm_fd, &data->fb[i]);
> -				data->plane[i] = NULL;
> -				break;
> -			}
> -		}
> -		max_planes = c;
> -		igt_assert_lt(0, max_planes);
>  
>  		mode_hi = igt_output_get_mode(output);
>  		mode_lo = get_lowres_mode(data, mode_hi, output); @@ -293,48 
> +287,35 @@ test_resolution_with_output(data_t *data, enum pipe pipe, 
> igt_output_t *output)
>  
>  		i++;
>  	}
> -
> -	return max_planes;
>  }
>  
>  static void
> -run_test(data_t *data, enum pipe pipe, igt_output_t *output)
> +run_test(data_t *data, enum pipe pipe, int max_planes, igt_output_t 
> +*output)
>  {
> -	int connected_outs;
> -	int n_planes = data->display.pipes[pipe].n_planes;
> -	int max_planes = n_planes;
> -
>  	if (!opt.user_seed)
>  		opt.seed = time(NULL);
>  
> -	connected_outs = 0;
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> -		igt_info("Testing resolution with connector %s using pipe %s with seed %d\n",
> -			 igt_output_name(output), kmstest_pipe_name(pipe), opt.seed);
> -
> -		test_init(data, pipe, n_planes, output);
> -		max_planes = test_resolution_with_output(data, pipe, output);
> -
> -		igt_fork(child, 1) {
> -			test_plane_position_with_output(data, pipe, max_planes, output);
> -		}
> +	igt_info("Testing resolution with connector %s using pipe %s with seed %d\n",
> +		 igt_output_name(output), kmstest_pipe_name(pipe), opt.seed);
>  
> -		test_resolution_with_output(data, pipe, output);
> +	test_init(data, pipe, max_planes, output);
> +	igt_fork(child, 1) {
> +		test_plane_position_with_output(data, pipe, max_planes, output);
> +	}
>  
> -		igt_waitchildren();
> +	test_resolution_with_output(data, pipe, output);
>  
> -		test_fini(data, pipe, n_planes, output);
> +	igt_waitchildren();
>  
> -		connected_outs++;
> -	}
> +	test_fini(data, pipe, max_planes, output);
>  
> -	igt_skip_on(connected_outs == 0);
>  }
>  
>  static void
>  run_tests_for_pipe(data_t *data, enum pipe pipe)  {
>  	igt_output_t *output;
> +	int max_planes;
>  
>  	igt_fixture {
>  		int valid_tests = 0;
> @@ -348,9 +329,18 @@ run_tests_for_pipe(data_t *data, enum pipe pipe)
>  		igt_require_f(valid_tests, "no valid crtc/connector combinations found\n");
>  	}
>  
> -	igt_subtest_f("pipe-%s", kmstest_pipe_name(pipe))
> -		for_each_valid_output_on_pipe(&data->display, pipe, output)
> -			run_test(data, pipe, output);
> +	igt_subtest_f("pipe-%s", kmstest_pipe_name(pipe)) {
> +		for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +			int n_planes = data->display.pipes[pipe].n_planes;
> +
> +			test_init(data, pipe, n_planes, output);
> +			max_planes = test_bandwidth(data, pipe, output);
> +			test_fini(data, pipe, n_planes, output);
> +
> +			igt_display_reset(&data->display);
> +			run_test(data, pipe, max_planes, output);
> +		}
> +	}
>  }
>  
>  static int opt_handler(int option, int option_index, void *input)
> --
> 2.20.1
> 
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