On Tue, May 31, 2022 at 6:56 PM Hans de Goede [off-list ref] wrote:

Hi,

On 5/30/22 13:34, Hsin-Yi Wang wrote:

quoted

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

quoted

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.

quoted

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.

Hmm I would expect the main drm/kms driver to register the drm_connector
object after probing the panel, right ?

So maybe this is a problem with the panel API? How about adding
separate callback to the panel API to get the orientation, which the
main drm/kms driver can then call before registering the connector ?

And then have the main drm/kms driver call
drm_connector_set_panel_orientation() with the returned orientation
on the connecter before registering it.

The new get_orientation callback for the panel should of course
be optional (IOW amy be NULL), so we probably want a small
helper for drivers using panel (sub)drivers to take care of
the process of getting the panel orientation from the panel
(if supported) and then setting it on the connector.

Hi Hans,

Thanks for the suggestion. I've sent a new version for this:
https://patchwork.kernel.org/project/dri-devel/patch/20220601081823.1038797-2-hsinyi@chromium.org/

Panel can implement the optional callback to return the orientation
property, while drm/kms driver will call a drm API to get the value
then they can call drm_connector_set_panel_orientation().
Panel .get_mode will still call drm_connector_set_panel_orientation()
but now it will be a no-op as the value was set by drm/kms driver
previously.

This is similar to the small patch below:
https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/
But it's now using the panel API.

quoted

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/

That is a suprisingly small patch (which is good). I guess that
my suggestion to add a new panel driver callback to get
the orientation would be a bit bigget then this. Still I think
that that would be a bit cleaner, as it would also solve this
for cases where the orientation comes from the panel itself
(through say some EDID extenstion) rather then from devicetree.

Still I think either way should be acceptable upstream.

Opinions from other drm devs on the above are very much welcome!

Your small patch nicely avoids the probe ordering problem,
so it is much better then this patch series.

Regards,

Hans

quoted

Thanks

quoted

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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