Re: [igt-dev] [PATCH V6 i-g-t 4/6] kms_writeback: Add writeback-check-output

["Ser, Simon" <simon.ser@intel.com>]

Mostly looks good, here are a few comments.

On Wed, 2019-06-12 at 23:17 -0300, Brian Starkey wrote:
> Add a test which makes commits using the writeback connector, and
> checks the output buffer hash to make sure it is/isn't written as
> appropriate.
> 
> Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> ---
>  tests/kms_writeback.c | 124 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 124 insertions(+)
> 
> diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> index 66ef48a6..0f20dadd 100644
> --- a/tests/kms_writeback.c
> +++ b/tests/kms_writeback.c
> @@ -30,6 +30,7 @@
>  #include "igt.h"
>  #include "igt_core.h"
>  #include "igt_fb.h"
> +#include "sw_sync.h"
>  
>  static drmModePropertyBlobRes *get_writeback_formats_blob(igt_output_t *output)
>  {
> @@ -221,6 +222,116 @@ static void writeback_fb_id(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t *
>  	igt_assert(ret == 0);
>  }
>  
> +static void fill_fb(igt_fb_t *fb, double color[3])
> +{
> +	cairo_t *cr = igt_get_cairo_ctx(fb->fd, fb);
> +	igt_assert(cr);
> +
> +	igt_paint_color(cr, 0, 0, fb->width, fb->height,
> +			color[0], color[1], color[2]);
> +}
> +
> +static void get_and_wait_out_fence(igt_output_t *output)
> +{
> +	int ret;
> +
> +	igt_assert(output->writeback_out_fence_fd >= 0);
> +
> +	ret = sync_fence_wait(output->writeback_out_fence_fd, 1000);
> +	igt_assert(ret == 0);

When filtering failures in CI Bug Log, "ret == 0" is not very helpful
and may not be unique. Can we add a descriptive error message, with
something among the lines of:

    igt_assert_f(ret == 0, "sync_fence_wait failed: %s\n", strerror(-ret));

> +	close(output->writeback_out_fence_fd);
> +	output->writeback_out_fence_fd = -1;
> +}
> +
> +static void writeback_sequence(igt_output_t *output, igt_plane_t *plane,
> +				igt_fb_t *in_fb, igt_fb_t *out_fbs[], int n_commits)
> +{
> +	int i, color_idx = 0;
> +	double in_fb_colors[2][3] = {
> +		{ 1.0, 0.0, 0.0 },
> +		{ 0.0, 1.0, 0.0 },
> +	};
> +	double clear_color[3] = { 1.0, 1.0, 1.0 };
> +	igt_crc_t cleared_crc, out_expected;
> +
> +	for (i = 0; i < n_commits; i++, color_idx++) {
> +		/* Change the input color each time */
> +		fill_fb(in_fb, in_fb_colors[color_idx % 2]);

Why do we need two indexes (i and color_idx)? I think [i % 2] should
work just fine.

> +		if (out_fbs[i]) {
> +			igt_crc_t out_before;
> +
> +			/* Get the expected CRC */
> +			fill_fb(out_fbs[i], in_fb_colors[color_idx % 2]);
> +			igt_fb_get_crc(out_fbs[i], &out_expected);

Using out_fbs[i] to compute the expected CRC is a little bit confusing.
I think we can just use in_fb here (which is already filled with the
proper color).

> +			fill_fb(out_fbs[i], clear_color);
> +			if (i == 0)
> +				igt_fb_get_crc(out_fbs[i], &cleared_crc);
> +			igt_fb_get_crc(out_fbs[i], &out_before);
> +			igt_assert_crc_equal(&cleared_crc, &out_before);
> +		}
> +
> +		/* Commit */
> +		igt_plane_set_fb(plane, in_fb);
> +		igt_output_set_writeback_fb(output, out_fbs[i]);
> +
> +		igt_display_commit_atomic(output->display,
> +					  DRM_MODE_ATOMIC_ALLOW_MODESET,
> +					  NULL);
> +		if (out_fbs[i])
> +			get_and_wait_out_fence(output);
> +
> +		/* Make sure the old output buffer is untouched */
> +		if (i > 0 && out_fbs[i - 1] && (out_fbs[i] != out_fbs[i - 1])) {

Nit: unnecessary parentheses here

> +			igt_crc_t out_prev;
> +			igt_fb_get_crc(out_fbs[i - 1], &out_prev);
> +			igt_assert_crc_equal(&cleared_crc, &out_prev);
> +		}
> +
> +		/* Make sure this output buffer is written */
> +		if (out_fbs[i]) {
> +			igt_crc_t out_after;
> +			igt_fb_get_crc(out_fbs[i], &out_after);
> +			igt_assert_crc_equal(&out_expected, &out_after);
> +
> +			/* And clear it, for the next time */
> +			fill_fb(out_fbs[i], clear_color);
> +		}
> +	}
> +}
> +
> +static void writeback_check_output(igt_output_t *output, igt_plane_t *plane,
> +				   igt_fb_t *input_fb, igt_fb_t *output_fb)
> +{
> +	igt_fb_t *out_fbs[2] = { 0 };
> +	igt_fb_t second_out_fb;
> +	int ret;
> +
> +	/* One commit, with a writeback. */
> +	writeback_sequence(output, plane, input_fb, &output_fb, 1);
> +
> +	/* Two commits, the second with no writeback */
> +	out_fbs[0] = output_fb;
> +	writeback_sequence(output, plane, input_fb, out_fbs, 2);
> +
> +	/* Two commits, both with writeback */
> +	out_fbs[1] = output_fb;
> +	writeback_sequence(output, plane, input_fb, out_fbs, 2);
> +
> +	ret = igt_create_fb(output_fb->fd, output_fb->width, output_fb->height,
> +			    DRM_FORMAT_XRGB8888,
> +			    igt_fb_mod_to_tiling(0),
> +			    &second_out_fb);
> +	igt_require(ret > 0);

unsigned int cast to int here

> +	/* Two commits, with different writeback buffers */
> +	out_fbs[1] = &second_out_fb;
> +	writeback_sequence(output, plane, input_fb, out_fbs, 2);
> +
> +	igt_remove_fb(output_fb->fd, &second_out_fb);
> +}
> +
>  igt_main
>  {
>  	igt_display_t display;
> @@ -307,6 +418,19 @@ igt_main
>  		igt_remove_fb(display.drm_fd, &output_fb);
>  	}
>  
> +	igt_subtest("writeback-check-output") {
> +		igt_fb_t output_fb;
> +		ret = igt_create_fb(display.drm_fd, mode.hdisplay, mode.vdisplay,
> +				    DRM_FORMAT_XRGB8888,
> +				    igt_fb_mod_to_tiling(0),
> +				    &output_fb);
> +		igt_require(ret > 0);

unsigned int cast to int here

> +		writeback_check_output(output, plane, &input_fb, &output_fb);
> +
> +		igt_remove_fb(display.drm_fd, &output_fb);
> +	}
> +
>  	igt_fixture {
>  		igt_remove_fb(display.drm_fd, &input_fb);
>  		igt_display_fini(&display);
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