Re: [PATCH v2 3/5] drm/modes: Allow to specify rotation and reflection on the commandline

[Maxime Ripard <maxime.ripard@bootlin.com>]

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On Wed, Apr 17, 2019 at 04:58:07PM +0200, Noralf Trønnes wrote:
> Den 17.04.2019 16.30, skrev Maxime Ripard:
> > On Tue, Apr 16, 2019 at 04:50:00PM +0200, Noralf Trønnes wrote:
> >> Den 11.04.2019 15.22, skrev Maxime Ripard:
> >>> Rotations and reflections setup are needed in some scenarios to initialise
> >>> properly the initial framebuffer. Some drivers already had a bunch of
> >>> quirks to deal with this, such as either a private kernel command line
> >>> parameter (omapdss) or on the device tree (various panels).
> >>>
> >>> In order to accomodate this, let's create a video mode parameter to deal
> >>> with the rotation and reflexion.
> >>>
> >>> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> >>> ---
> >>>  drivers/gpu/drm/drm_fb_helper.c |   4 +-
> >>>  drivers/gpu/drm/drm_modes.c     | 110 +++++++++++++++++++++++++++------
> >>>  include/drm/drm_connector.h     |   1 +-
> >>>  3 files changed, 95 insertions(+), 20 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> >>> index b3a5d79436ae..8781897559b2 100644
> >>> --- a/drivers/gpu/drm/drm_fb_helper.c
> >>> +++ b/drivers/gpu/drm/drm_fb_helper.c
> >>> @@ -2521,6 +2521,7 @@ static void drm_setup_crtc_rotation(struct drm_fb_helper *fb_helper,
> >>>  				    struct drm_connector *connector)
> >>>  {
> >>>  	struct drm_plane *plane = fb_crtc->mode_set.crtc->primary;
> >>> +	struct drm_cmdline_mode *mode = &connector->cmdline_mode;
> >>>  	uint64_t valid_mask = 0;
> >>>  	int i, rotation;
> >>>
> >>> @@ -2540,6 +2541,9 @@ static void drm_setup_crtc_rotation(struct drm_fb_helper *fb_helper,
> >>>  		rotation = DRM_MODE_ROTATE_0;
> >>>  	}
> >>>
> >>> +	if (mode->rotation != DRM_MODE_ROTATE_0)
> >>> +		fb_crtc->rotation = mode->rotation;
> >>> +
> >>
> >> We already have a property to describe initial display/panel rotation.
> >> If we can set connector->display_info.panel_orientation from the video=
> >> parameter, then there's no need to modify drm_fb_helper, it will just work.
> >>
> >> In that case, maybe 'orientation' is a better argument name with values
> >> mapped to the enum.
> >
> > I wouldn't put it at the same level though. As far as I understand it,
> > the orientation is a hardware constraint: the hardware has been
> > designed that way, and should honor that orientation to make it look
> > with the top, well, on top.
> >
> > However, the rotation is more of a user choice, and you could
> > definitely envision having a combination of a rotation and an
> > orientation constraint.
> >
>
> Does this rotation only apply to the fbdev emulation and should not
> propogate to DRM userspace?

I guess it definitely should be propagated to the DRM userspace.

> I actually don't understand how the DRM plane rotation works for 90/270
> rotation. Should the framebuffer width/height be swapped when attaching
> to a rotated plane?

I'm not sure either, especially since the stride might be a bit
different too. However, since (as you pointed out) it would be much
harder to support, I left it out of that patch series for the moment.

> Btw drm_setup_crtc_rotation() doesn't support 90/270 plane rotation even
> if the hw supports it. It will instead sw rotate fbcon, but fbdev
> userspace remains unrotated.

That would need to be addressed eventually yep.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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