Re: [PATCH hwc v2 16/18] drm_hwcomposer: Find writeback connector for scene flattening

[Sean Paul <seanpaul@chromium.org>]

On Wed, Apr 11, 2018 at 04:22:27PM +0100, Alexandru Gheorghe wrote:
> Add logic for finding a suitable writeback connector, there are two
> possibilities for finding an usable writeback connector:
> 
> 1) Attached to the same CRTC as the display and can function
>    concurrently with the display connector.
> 
> 2) On a different CRTC and the display connector is not used (state !=
> DRM_MODE_CONNECTED). What's not handled here and should be handle is
> what happens if connector changes state while flattening, but since
> hotplug is not wired yet, it's not something we should worry about.
> 
> Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
> ---
>  drmresources.cpp    | 25 +++++++++++++++++++++++++
>  drmresources.h      |  2 +-
>  resourcemanager.cpp | 24 ++++++++++++++++++++++++
>  resourcemanager.h   |  1 +
>  4 files changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drmresources.cpp b/drmresources.cpp
> index fef6835..70126a4 100644
> --- a/drmresources.cpp
> +++ b/drmresources.cpp
> @@ -269,6 +269,31 @@ DrmConnector *DrmResources::GetWritebackConnectorForDisplay(int display) const {
>    return NULL;
>  }
>  
> +// TODO what happens when hotplugging
> +DrmConnector *DrmResources::AvailableWritebackConnector(int display) const {
> +  DrmConnector *writeback_conn = GetWritebackConnectorForDisplay(display);
> +  DrmConnector *display_conn = GetConnectorForDisplay(display);
> +  // If we have a writeback already attached to the same CRTC, just use that, if
> +  // possible
> +  if (display_conn && writeback_conn &&
> +      writeback_conn->encoder()->can_clone(display_conn->encoder()))
> +    return writeback_conn;
> +
> +  // Use another CRTC if available and doesn't have any connector
> +  for (auto &crtc : crtcs_) {
> +    if (crtc->display() == display)
> +      continue;
> +    display_conn = GetConnectorForDisplay(crtc->display());
> +    // If we have a display connected don't use it for writeback
> +    if (display_conn && display_conn->state() == DRM_MODE_CONNECTED)
> +      continue;
> +    writeback_conn = GetWritebackConnectorForDisplay(crtc->display());
> +    if (writeback_conn)
> +      return writeback_conn;
> +  }
> +  return NULL;
> +}
> +
>  DrmCrtc *DrmResources::GetCrtcForDisplay(int display) const {
>    for (auto &crtc : crtcs_) {
>      if (crtc->display() == display)
> diff --git a/drmresources.h b/drmresources.h
> index 4fb17fc..9176b8e 100644
> --- a/drmresources.h
> +++ b/drmresources.h
> @@ -60,7 +60,7 @@ class DrmResources {
>  
>    DrmConnector *GetConnectorForDisplay(int display) const;
>    DrmConnector *GetWritebackConnectorForDisplay(int display) const;
> -  DrmConnector *FindWritebackConnector(int display) const;

What's up with this?

> +  DrmConnector *AvailableWritebackConnector(int display) const;
>    DrmCrtc *GetCrtcForDisplay(int display) const;
>    DrmPlane *GetPlane(uint32_t id) const;
>    DrmEventListener *event_listener();
> diff --git a/resourcemanager.cpp b/resourcemanager.cpp
> index e7b654e..b2a4458 100644
> --- a/resourcemanager.cpp
> +++ b/resourcemanager.cpp
> @@ -49,6 +49,30 @@ int ResourceManager::Init() {
>                         (const hw_module_t **)&gralloc_);
>  }
>  
> +DrmConnector *ResourceManager::AvailableWritebackConnector(int display) {
> +  DrmResources *drm_resource = GetDrmResources(display);
> +  DrmConnector *writeback_conn = NULL;
> +  if (drm_resource) {
> +    writeback_conn = drm_resource->AvailableWritebackConnector(display);
> +    if (writeback_conn) {
> +      ALOGI("Use writeback connected to display %d\n",
> +            writeback_conn->display());

This seems a little chatty, it's written every flatten, yeah?

> +      return writeback_conn;
> +    }
> +  }
> +  for (auto &drm : drms_) {
> +    if (drm.get() == drm_resource)
> +      continue;
> +    writeback_conn = drm->AvailableWritebackConnector(display);
> +    if (writeback_conn) {
> +      ALOGI("Use writeback connected to display %d\n",
> +            writeback_conn->display());
> +      return writeback_conn;
> +    }
> +  }
> +  return writeback_conn;
> +}
> +
>  DrmResources *ResourceManager::GetDrmResources(int display) {
>    for (uint32_t i = 0; i < drms_.size(); i++) {
>      if (drms_[i]->HandlesDisplay(display))
> diff --git a/resourcemanager.h b/resourcemanager.h
> index b8caa9a..57f7a2a 100644
> --- a/resourcemanager.h
> +++ b/resourcemanager.h
> @@ -18,6 +18,7 @@ class ResourceManager {
>    DrmResources *GetDrmResources(int display);
>    std::shared_ptr<Importer> GetImporter(int display);
>    const gralloc_module_t *GetGralloc();
> +  DrmConnector *AvailableWritebackConnector(int display);
>  
>   private:
>    std::vector<std::unique_ptr<DrmResources>> drms_;
> -- 
> 2.7.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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