diff mbox series

[v7,i-g-t,4/4] kms_writeback: Add writeback-check-output

Message ID 20191022010032.pgqop52v4gz5omlc@smtp.gmail.com (mailing list archive)
State New, archived
Headers show
Series Add support for testing writeback connectors | expand

Commit Message

Rodrigo Siqueira Oct. 22, 2019, 1 a.m. UTC
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.

V6: Simon Ser
 - Add igt documentation with igt_describe
 - Replace int ret by unsigned int fd_id when calling igt_create_fb
 - Add a descriptive error message if sync_fence_wait fail
 - Replace color_idx variable by i
 - Use in_fb instead of out_fb for getting the expected CRC
 - Drop unnecessary parentheses
 - Replace igt_fb_mod_to_tiling to DRM_FORMAT_MOD_LINEAR

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
[rebased and updated the patch to address feedback]
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
---
 tests/kms_writeback.c | 123 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

Comments

Maxime Ripard April 15, 2020, 9:45 a.m. UTC | #1
Hi!

On Mon, Oct 21, 2019 at 10:00:39PM -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.
>
> V6: Simon Ser
>  - Add igt documentation with igt_describe
>  - Replace int ret by unsigned int fd_id when calling igt_create_fb
>  - Add a descriptive error message if sync_fence_wait fail
>  - Replace color_idx variable by i
>  - Use in_fb instead of out_fb for getting the expected CRC
>  - Drop unnecessary parentheses
>  - Replace igt_fb_mod_to_tiling to DRM_FORMAT_MOD_LINEAR
>
> Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> [rebased and updated the patch to address feedback]
> Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> ---
>  tests/kms_writeback.c | 123 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 123 insertions(+)
>
> diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> index a373ec4d..068595b9 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"
>
>  IGT_TEST_DESCRIPTION("Exercise writeback feature.");
>
> @@ -196,6 +197,115 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
>  	igt_assert(ret == -EINVAL);
>  }
>
> +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]);
> +}
> +

On which platform did you test this? On Arm (but I would assume
anything !i915), this will fire up an assert.

I've replaced this with a igt_fb_map_buffer/memset, and it works as
expected.

Maxime
Rodrigo Siqueira April 21, 2020, 9:07 p.m. UTC | #2
On 04/15, Maxime Ripard wrote:
> Hi!
> 
> On Mon, Oct 21, 2019 at 10:00:39PM -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.
> >
> > V6: Simon Ser
> >  - Add igt documentation with igt_describe
> >  - Replace int ret by unsigned int fd_id when calling igt_create_fb
> >  - Add a descriptive error message if sync_fence_wait fail
> >  - Replace color_idx variable by i
> >  - Use in_fb instead of out_fb for getting the expected CRC
> >  - Drop unnecessary parentheses
> >  - Replace igt_fb_mod_to_tiling to DRM_FORMAT_MOD_LINEAR
> >
> > Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> > [rebased and updated the patch to address feedback]
> > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> > ---
> >  tests/kms_writeback.c | 123 ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 123 insertions(+)
> >
> > diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> > index a373ec4d..068595b9 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"
> >
> >  IGT_TEST_DESCRIPTION("Exercise writeback feature.");
> >
> > @@ -196,6 +197,115 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
> >  	igt_assert(ret == -EINVAL);
> >  }
> >
> > +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]);
> > +}
> > +
> 
> On which platform did you test this? On Arm (but I would assume
> anything !i915), this will fire up an assert.
> 
> I've replaced this with a igt_fb_map_buffer/memset, and it works as
> expected.

Hi,

Could you share your fix for this issue? Since you already have a
solution that you know that works on ARM, I can just use it for avoiding
an unnecessary round of review in the next version.

Thanks
 
> Maxime
Maxime Ripard April 22, 2020, 6:03 p.m. UTC | #3
Hi!

On Tue, Apr 21, 2020 at 05:07:05PM -0400, Rodrigo Siqueira wrote:
> On 04/15, Maxime Ripard wrote:
> > On Mon, Oct 21, 2019 at 10:00:39PM -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.
> > >
> > > V6: Simon Ser
> > >  - Add igt documentation with igt_describe
> > >  - Replace int ret by unsigned int fd_id when calling igt_create_fb
> > >  - Add a descriptive error message if sync_fence_wait fail
> > >  - Replace color_idx variable by i
> > >  - Use in_fb instead of out_fb for getting the expected CRC
> > >  - Drop unnecessary parentheses
> > >  - Replace igt_fb_mod_to_tiling to DRM_FORMAT_MOD_LINEAR
> > >
> > > Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> > > [rebased and updated the patch to address feedback]
> > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> > > ---
> > >  tests/kms_writeback.c | 123 ++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 123 insertions(+)
> > >
> > > diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> > > index a373ec4d..068595b9 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"
> > >
> > >  IGT_TEST_DESCRIPTION("Exercise writeback feature.");
> > >
> > > @@ -196,6 +197,115 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
> > >  	igt_assert(ret == -EINVAL);
> > >  }
> > >
> > > +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]);
> > > +}
> > > +
> > 
> > On which platform did you test this? On Arm (but I would assume
> > anything !i915), this will fire up an assert.
> > 
> > I've replaced this with a igt_fb_map_buffer/memset, and it works as
> > expected.
>
> Could you share your fix for this issue? Since you already have a
> solution that you know that works on ARM, I can just use it for avoiding
> an unnecessary round of review in the next version.

Sure, you'll find it attached

Maxime
diff --git a/lib/igt_fb.c b/lib/igt_fb.c
index 97a656c8..be825220 100644
--- a/lib/igt_fb.c
+++ b/lib/igt_fb.c
@@ -3812,12 +3812,9 @@ int igt_fb_get_crc(struct igt_fb *fb, igt_crc_t *crc)
 	if (fb->num_planes != 1)
 		return -EINVAL;
 
-	if (fb->is_dumb)
-		ptr = kmstest_dumb_map_buffer(fb->fd, fb->gem_handle, fb->size,
-					      PROT_READ);
-	else
-		ptr = gem_mmap__gtt(fb->fd, fb->gem_handle, fb->size,
-				    PROT_READ);
+	ptr = igt_fb_map_buffer(fb->fd, fb);
+	igt_assert(ptr);
+	map = ptr;
 
 	/*
 	 * Framebuffers are often uncached, which can make byte-wise accesses
@@ -3846,7 +3843,7 @@ int igt_fb_get_crc(struct igt_fb *fb, igt_crc_t *crc)
 	crc->crc[0] = hash;
 
 	free(line);
-	munmap(map, fb->size);
+	igt_fb_unmap_buffer(fb, map);
 
 	return 0;
 #undef FNV1a_OFFSET_BIAS
diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
index 068595b9..c2ee05dd 100644
--- a/tests/kms_writeback.c
+++ b/tests/kms_writeback.c
@@ -149,7 +149,7 @@ static int do_writeback_test(igt_output_t *output, uint32_t fb_id,
 
 	igt_output_set_prop_value(output, IGT_CONNECTOR_CRTC_ID, config->crtc->crtc_id);
 	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_FB_ID, fb_id);
-	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR, (uint64_t)out_fence_ptr);
+	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR, (uint64_t)(uintptr_t)out_fence_ptr);
 
 	if (ptr_valid)
 		*out_fence_ptr = 0;
@@ -197,13 +197,18 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
 	igt_assert(ret == -EINVAL);
 }
 
-static void fill_fb(igt_fb_t *fb, double color[3])
+static void fill_fb(igt_fb_t *fb, uint32_t pixel)
 {
-	cairo_t *cr = igt_get_cairo_ctx(fb->fd, fb);
-	igt_assert(cr);
+	void *ptr;
 
-	igt_paint_color(cr, 0, 0, fb->width, fb->height,
-			color[0], color[1], color[2]);
+	igt_assert(fb->drm_format == DRM_FORMAT_XRGB8888);
+
+	ptr = igt_fb_map_buffer(fb->fd, fb);
+	igt_assert(ptr);
+
+	memset(ptr, pixel, fb->strides[0] * fb->height); 
+
+	igt_fb_unmap_buffer(fb, ptr);
 }
 
 static void get_and_wait_out_fence(igt_output_t *output)
@@ -222,11 +227,8 @@ 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;
-	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 };
+	uint32_t in_fb_colors[2] = { 0xffff0000, 0xff00ff00 };
+	uint32_t clear_color = 0xffffffff;
 	igt_crc_t cleared_crc, out_expected;
 
 	for (i = 0; i < n_commits; i++) {
Rodrigo Siqueira April 23, 2020, 12:04 p.m. UTC | #4
On 04/22, Maxime Ripard wrote:
> Hi!
> 
> On Tue, Apr 21, 2020 at 05:07:05PM -0400, Rodrigo Siqueira wrote:
> > On 04/15, Maxime Ripard wrote:
> > > On Mon, Oct 21, 2019 at 10:00:39PM -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.
> > > >
> > > > V6: Simon Ser
> > > >  - Add igt documentation with igt_describe
> > > >  - Replace int ret by unsigned int fd_id when calling igt_create_fb
> > > >  - Add a descriptive error message if sync_fence_wait fail
> > > >  - Replace color_idx variable by i
> > > >  - Use in_fb instead of out_fb for getting the expected CRC
> > > >  - Drop unnecessary parentheses
> > > >  - Replace igt_fb_mod_to_tiling to DRM_FORMAT_MOD_LINEAR
> > > >
> > > > Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> > > > [rebased and updated the patch to address feedback]
> > > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
> > > > ---
> > > >  tests/kms_writeback.c | 123 ++++++++++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 123 insertions(+)
> > > >
> > > > diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> > > > index a373ec4d..068595b9 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"
> > > >
> > > >  IGT_TEST_DESCRIPTION("Exercise writeback feature.");
> > > >
> > > > @@ -196,6 +197,115 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
> > > >  	igt_assert(ret == -EINVAL);
> > > >  }
> > > >
> > > > +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]);
> > > > +}
> > > > +
> > > 
> > > On which platform did you test this? On Arm (but I would assume
> > > anything !i915), this will fire up an assert.
> > > 
> > > I've replaced this with a igt_fb_map_buffer/memset, and it works as
> > > expected.
> >
> > Could you share your fix for this issue? Since you already have a
> > solution that you know that works on ARM, I can just use it for avoiding
> > an unnecessary round of review in the next version.
> 
> Sure, you'll find it attached

Thanks!

I'm going to submit a new version today.

Best Regards
 
> Maxime

> diff --git a/lib/igt_fb.c b/lib/igt_fb.c
> index 97a656c8..be825220 100644
> --- a/lib/igt_fb.c
> +++ b/lib/igt_fb.c
> @@ -3812,12 +3812,9 @@ int igt_fb_get_crc(struct igt_fb *fb, igt_crc_t *crc)
>  	if (fb->num_planes != 1)
>  		return -EINVAL;
>  
> -	if (fb->is_dumb)
> -		ptr = kmstest_dumb_map_buffer(fb->fd, fb->gem_handle, fb->size,
> -					      PROT_READ);
> -	else
> -		ptr = gem_mmap__gtt(fb->fd, fb->gem_handle, fb->size,
> -				    PROT_READ);
> +	ptr = igt_fb_map_buffer(fb->fd, fb);
> +	igt_assert(ptr);
> +	map = ptr;
>  
>  	/*
>  	 * Framebuffers are often uncached, which can make byte-wise accesses
> @@ -3846,7 +3843,7 @@ int igt_fb_get_crc(struct igt_fb *fb, igt_crc_t *crc)
>  	crc->crc[0] = hash;
>  
>  	free(line);
> -	munmap(map, fb->size);
> +	igt_fb_unmap_buffer(fb, map);
>  
>  	return 0;
>  #undef FNV1a_OFFSET_BIAS
> diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> index 068595b9..c2ee05dd 100644
> --- a/tests/kms_writeback.c
> +++ b/tests/kms_writeback.c
> @@ -149,7 +149,7 @@ static int do_writeback_test(igt_output_t *output, uint32_t fb_id,
>  
>  	igt_output_set_prop_value(output, IGT_CONNECTOR_CRTC_ID, config->crtc->crtc_id);
>  	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_FB_ID, fb_id);
> -	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR, (uint64_t)out_fence_ptr);
> +	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR, (uint64_t)(uintptr_t)out_fence_ptr);
>  
>  	if (ptr_valid)
>  		*out_fence_ptr = 0;
> @@ -197,13 +197,18 @@ static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
>  	igt_assert(ret == -EINVAL);
>  }
>  
> -static void fill_fb(igt_fb_t *fb, double color[3])
> +static void fill_fb(igt_fb_t *fb, uint32_t pixel)
>  {
> -	cairo_t *cr = igt_get_cairo_ctx(fb->fd, fb);
> -	igt_assert(cr);
> +	void *ptr;
>  
> -	igt_paint_color(cr, 0, 0, fb->width, fb->height,
> -			color[0], color[1], color[2]);
> +	igt_assert(fb->drm_format == DRM_FORMAT_XRGB8888);
> +
> +	ptr = igt_fb_map_buffer(fb->fd, fb);
> +	igt_assert(ptr);
> +
> +	memset(ptr, pixel, fb->strides[0] * fb->height); 
> +
> +	igt_fb_unmap_buffer(fb, ptr);
>  }
>  
>  static void get_and_wait_out_fence(igt_output_t *output)
> @@ -222,11 +227,8 @@ 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;
> -	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 };
> +	uint32_t in_fb_colors[2] = { 0xffff0000, 0xff00ff00 };
> +	uint32_t clear_color = 0xffffffff;
>  	igt_crc_t cleared_crc, out_expected;
>  
>  	for (i = 0; i < n_commits; i++) {
diff mbox series

Patch

diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
index a373ec4d..068595b9 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"
 
 IGT_TEST_DESCRIPTION("Exercise writeback feature.");
 
@@ -196,6 +197,115 @@  static void writeback_test_fb(igt_output_t *output, igt_fb_t *valid_fb, igt_fb_t
 	igt_assert(ret == -EINVAL);
 }
 
+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_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;
+	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++) {
+		/* Change the input color each time */
+		fill_fb(in_fb, in_fb_colors[i % 2]);
+
+		if (out_fbs[i]) {
+			igt_crc_t out_before;
+
+			/* Get the expected CRC */
+			igt_fb_get_crc(in_fb, &out_expected);
+
+			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]) {
+			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;
+	unsigned int fb_id;
+
+	/* 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);
+
+	fb_id = igt_create_fb(output_fb->fd,
+			      output_fb->width, output_fb->height,
+			      DRM_FORMAT_XRGB8888,
+			      DRM_FORMAT_MOD_LINEAR, &second_out_fb);
+	igt_require(fb_id > 0);
+
+	/* 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;
@@ -283,6 +393,19 @@  igt_main
 		igt_remove_fb(display.drm_fd, &invalid_fb);
 	}
 
+	igt_describe("Check writeback output with CRC validation");
+	igt_subtest("writeback-check-output") {
+		igt_fb_t output_fb;
+		fb_id = igt_create_fb(display.drm_fd, mode.hdisplay,
+				      mode.vdisplay, DRM_FORMAT_XRGB8888,
+				      DRM_FORMAT_MOD_LINEAR, &output_fb);
+		igt_require(fb_id > 0);
+
+		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);