Re: [PATCH v2 4/8] drm: vkms: Add fb information to `vkms_writeback_job`

[Igor Torrente]

Hi Thomas,

On 11/3/21 12:45 PM, Thomas Zimmermann wrote:

Hi

Am 26.10.21 um 13:34 schrieb Igor Torrente:

This commit is the groundwork to introduce new formats to the planes and
writeback buffer. As part of it, a new buffer metadata field is added to
`vkms_writeback_job`, this metadata is represented by the `vkms_composer`
struct.

This will allow us, in the future, to have different compositing and wb
format types.

Signed-off-by: Igor Torrente <igormtorre...@gmail.com>
---
V2: Change the code to get the drm_framebuffer reference and not copy its
      contents(Thomas Zimmermann).
---
   drivers/gpu/drm/vkms/vkms_composer.c  |  4 ++--
   drivers/gpu/drm/vkms/vkms_drv.h       | 12 ++++++------
   drivers/gpu/drm/vkms/vkms_plane.c     | 10 +++++-----
   drivers/gpu/drm/vkms/vkms_writeback.c | 21 ++++++++++++++++++---
   4 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c 
b/drivers/gpu/drm/vkms/vkms_composer.c
index 82f79e508f81..383ca657ddf7 100644
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -153,7 +153,7 @@ static void compose_plane(struct vkms_composer 
*primary_composer,
                          struct vkms_composer *plane_composer,
                          void *vaddr_out)
   {
-       struct drm_framebuffer *fb = &plane_composer->fb;
+       struct drm_framebuffer *fb = plane_composer->fb;
        void *vaddr;
        void (*pixel_blend)(const u8 *p_src, u8 *p_dst);

@@ -174,7 +174,7 @@ static int compose_active_planes(void **vaddr_out,

                                 struct vkms_composer *primary_composer,
                                 struct vkms_crtc_state *crtc_state)
   {
-       struct drm_framebuffer *fb = &primary_composer->fb;
+       struct drm_framebuffer *fb = primary_composer->fb;
        struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
        const void *vaddr;
        int i;
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 64e62993b06f..9e4c1e95bbb1 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -20,13 +20,8 @@
   #define XRES_MAX  8192
   #define YRES_MAX  8192

-struct vkms_writeback_job {

-       struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
-       struct dma_buf_map data[DRM_FORMAT_MAX_PLANES];
-};
-
   struct vkms_composer {
-       struct drm_framebuffer fb;
+       struct drm_framebuffer *fb;
        struct drm_rect src, dst;
        struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
        unsigned int offset;
@@ -34,6 +29,11 @@ struct vkms_composer {
        unsigned int cpp;
   };

+struct vkms_writeback_job {

+       struct dma_buf_map data[DRM_FORMAT_MAX_PLANES];
+       struct vkms_composer composer;
+};
+
   /**
    * vkms_plane_state - Driver specific plane state
    * @base: base plane state
diff --git a/drivers/gpu/drm/vkms/vkms_plane.c 
b/drivers/gpu/drm/vkms/vkms_plane.c
index 32409e15244b..0a28cb7a85e2 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -50,12 +50,12 @@ static void vkms_plane_destroy_state(struct drm_plane 
*plane,
        struct vkms_plane_state *vkms_state = to_vkms_plane_state(old_state);
        struct drm_crtc *crtc = vkms_state->base.base.crtc;

- if (crtc) {

+       if (crtc && vkms_state->composer->fb) {
                /* dropping the reference we acquired in
                 * vkms_primary_plane_update()
                 */
-               if (drm_framebuffer_read_refcount(&vkms_state->composer->fb))
-                       drm_framebuffer_put(&vkms_state->composer->fb);
+               if (drm_framebuffer_read_refcount(vkms_state->composer->fb))
+                       drm_framebuffer_put(vkms_state->composer->fb);
        }

kfree(vkms_state->composer);

@@ -110,9 +110,9 @@ static void vkms_plane_atomic_update(struct drm_plane 
*plane,
        composer = vkms_plane_state->composer;
        memcpy(&composer->src, &new_state->src, sizeof(struct drm_rect));
        memcpy(&composer->dst, &new_state->dst, sizeof(struct drm_rect));
-       memcpy(&composer->fb, fb, sizeof(struct drm_framebuffer));
+       composer->fb = fb;
        memcpy(&composer->map, &shadow_plane_state->data, 
sizeof(composer->map));
-       drm_framebuffer_get(&composer->fb);
+       drm_framebuffer_get(composer->fb);
        composer->offset = fb->offsets[0];
        composer->pitch = fb->pitches[0];
        composer->cpp = fb->format->cpp[0];
diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c 
b/drivers/gpu/drm/vkms/vkms_writeback.c
index 8694227f555f..32734cdbf6c2 100644
--- a/drivers/gpu/drm/vkms/vkms_writeback.c
+++ b/drivers/gpu/drm/vkms/vkms_writeback.c
@@ -75,12 +75,15 @@ static int vkms_wb_prepare_job(struct 
drm_writeback_connector *wb_connector,
        if (!vkmsjob)
                return -ENOMEM;

- ret = drm_gem_fb_vmap(job->fb, vkmsjob->map, vkmsjob->data);

+       ret = drm_gem_fb_vmap(job->fb, vkmsjob->composer.map, vkmsjob->data);
        if (ret) {
                DRM_ERROR("vmap failed: %d\n", ret);
                goto err_kfree;
        }

+ vkmsjob->composer.fb = job->fb;

+       drm_framebuffer_get(vkmsjob->composer.fb);
+
        job->priv = vkmsjob;

return 0;

@@ -99,7 +102,10 @@ static void vkms_wb_cleanup_job(struct 
drm_writeback_connector *connector,
        if (!job->fb)
                return;

- drm_gem_fb_vunmap(job->fb, vkmsjob->map);

+       drm_gem_fb_vunmap(job->fb, vkmsjob->composer.map);
+
+       if (drm_framebuffer_read_refcount(vkmsjob->composer.fb))
+               drm_framebuffer_put(vkmsjob->composer.fb);

Why is this protected by an if conditional?

Here, I followed what was done in the vkms_plane code, just adapting it
to the writeback callbacks.

I put this if because I wasn't 100% sure that for each
`vkms_wb_prepare_job` I would have exactly one `vkms_wb_cleanup_job`
after it.

It happened in my testings, but I can't guarantee that it will always
happen.

Best regards
Thomas

vkmsdev = drm_device_to_vkms_device(job->fb->dev);

        vkms_set_composer(&vkmsdev->output, false);
@@ -116,14 +122,23 @@ static void vkms_wb_atomic_commit(struct drm_connector 
*conn,
        struct drm_writeback_connector *wb_conn = &output->wb_connector;
        struct drm_connector_state *conn_state = wb_conn->base.state;
        struct vkms_crtc_state *crtc_state = output->composer_state;
+       struct drm_framebuffer *fb = connector_state->writeback_job->fb;
+       struct vkms_writeback_job *active_wb;
+       struct vkms_composer *wb_composer;

if (!conn_state)

                return;

vkms_set_composer(&vkmsdev->output, true); + active_wb = conn_state->writeback_job->priv;

+       wb_composer = &active_wb->composer;
+
        spin_lock_irq(&output->composer_lock);
-       crtc_state->active_writeback = conn_state->writeback_job->priv;
+       crtc_state->active_writeback = active_wb;
+       wb_composer->offset = fb->offsets[0];
+       wb_composer->pitch = fb->pitches[0];
+       wb_composer->cpp = fb->format->cpp[0];
        crtc_state->wb_pending = true;
        spin_unlock_irq(&output->composer_lock);
        drm_writeback_queue_job(wb_conn, connector_state);

Thanks,
---
Igor M. A. Torrente