On Mon, May 30, 2022 at 4:53 PM Hans de Goede [off-list ref] wrote:

Hi,

On 5/30/22 10:19, Hsin-Yi Wang wrote:

quoted

Some drivers, eg. mtk_drm and msm_drm, rely on the panel to set the
orientation. Panel calls drm_connector_set_panel_orientation() to create
orientation property and sets the value. However, connector properties
can't be created after drm_dev_register() is called. The goal is to
separate the orientation property creation, so drm drivers can create it
earlier before drm_dev_register().

Sorry for jumping in pretty late in the discussion (based on the v10
I seem to have missed this before).

This sounds to me like the real issue here is that drm_dev_register()
is getting called too early?

Right.

To me it seems sensible to delay calling drm_dev_register() and
thus allowing userspace to start detecting available displays +
features until after the panel has been probed.

Most panels set this value very late, in .get_modes callback (since it
is when the connector is known), though the value was known during
panel probe.

I think we can also let drm check if they have remote panel nodes: If
there is a panel and the panel sets the orientation, let the drm read
this value and set the property. Does this workflow sound reasonable?

The corresponding patch to implement this:
https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/

Thanks

I see a devicetree patch in this series, so I guess that the panel
is described in devicetree. Especially in the case of devicetree
I would expect the kernel to have enough info to do the right
thing and make sure the panel is probed before calling
drm_dev_register() ?

Regards,

Hans

quoted

After this series, drm_connector_set_panel_orientation() works like
before. It won't affect existing callers of
drm_connector_set_panel_orientation(). The only difference is that
some drm drivers can call drm_connector_init_panel_orientation_property()
earlier.

Hsin-Yi Wang (4):
  gpu: drm: separate panel orientation property creating and value
    setting
  drm/mediatek: init panel orientation property
  drm/msm: init panel orientation property
  arm64: dts: mt8183: Add panel rotation

 .../arm64/boot/dts/mediatek/mt8183-kukui.dtsi |  1 +
 drivers/gpu/drm/drm_connector.c               | 58 ++++++++++++++-----
 drivers/gpu/drm/mediatek/mtk_dsi.c            |  7 +++
 drivers/gpu/drm/msm/dsi/dsi_manager.c         |  4 ++
 include/drm/drm_connector.h                   |  2 +
 5 files changed, 59 insertions(+), 13 deletions(-)

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