Re: [PATCH v4 3/3] drm: Add helper for simple display pipeline

[Ville Syrjälä]

On Tue, May 17, 2016 at 02:00:45PM +0200, Noralf Trønnes wrote:
> 
> Den 17.05.2016 09:59, skrev Daniel Vetter:
> > On Tue, May 17, 2016 at 10:46:51AM +0300, Ville Syrjälä wrote:
> >> On Tue, May 17, 2016 at 09:05:01AM +0200, Daniel Vetter wrote:
> >>> On Thu, May 12, 2016 at 09:36:14PM +0300, Ville Syrjälä wrote:
> >>>> On Thu, May 12, 2016 at 08:25:23PM +0200, Noralf Trønnes wrote:
> >>>>> Provides helper functions for drivers that have a simple display
> >>>>> pipeline. Plane, crtc and encoder are collapsed into one entity.
> >>>>>
> >>>>> Cc: jsarha@xxxxxx
> >>>>> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> >>>>> ---
> >>>>>
> >>>>> Changes since v3:
> >>>>> - (struct drm_simple_display_pipe *)->funcs should be const
> >>>>>
> >>>>> Changes since v2:
> >>>>> - Drop Kconfig knob DRM_KMS_HELPER
> >>>>> - Expand documentation
> >>>>>
> >>>>> Changes since v1:
> >>>>> - Add DOC header and add to gpu.tmpl
> >>>>> - Fix docs: @funcs is optional, "negative error code",
> >>>>>    "This hook is optional."
> >>>>> - Add checks to drm_simple_kms_plane_atomic_check()
> >>>>>
> >>>>>   Documentation/DocBook/gpu.tmpl          |   6 +
> >>>>>   drivers/gpu/drm/Makefile                |   2 +-
> >>>>>   drivers/gpu/drm/drm_simple_kms_helper.c | 208 ++++++++++++++++++++++++++++++++
> >>>>>   include/drm/drm_simple_kms_helper.h     |  94 +++++++++++++++
> >>>>>   4 files changed, 309 insertions(+), 1 deletion(-)
> >>>>>   create mode 100644 drivers/gpu/drm/drm_simple_kms_helper.c
> >>>>>   create mode 100644 include/drm/drm_simple_kms_helper.h
> >>>>>
> >>>>> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> >>>>> index 4a0c599..cf3f5a8 100644
> >>>>> --- a/Documentation/DocBook/gpu.tmpl
> >>>>> +++ b/Documentation/DocBook/gpu.tmpl
> >>>>> @@ -1693,6 +1693,12 @@ void intel_crt_init(struct drm_device *dev)
> >>>>>   !Edrivers/gpu/drm/drm_panel.c
> >>>>>   !Pdrivers/gpu/drm/drm_panel.c drm panel
> >>>>>       </sect2>
> >>>>> +    <sect2>
> >>>>> +      <title>Simple KMS Helper Reference</title>
> >>>>> +!Iinclude/drm/drm_simple_kms_helper.h
> >>>>> +!Edrivers/gpu/drm/drm_simple_kms_helper.c
> >>>>> +!Pdrivers/gpu/drm/drm_simple_kms_helper.c overview
> >>>>> +    </sect2>
> >>>>>     </sect1>
> >>>>>
> >>>>>     <!-- Internals: kms properties -->
> >>>>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> >>>>> index 2bd3e5a..31b85df5 100644
> >>>>> --- a/drivers/gpu/drm/Makefile
> >>>>> +++ b/drivers/gpu/drm/Makefile
> >>>>> @@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
> >>>>>
> >>>>>   drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
> >>>>>   		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
> >>>>> -		drm_kms_helper_common.o
> >>>>> +		drm_kms_helper_common.o drm_simple_kms_helper.o
> >>>>>
> >>>>>   drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> >>>>>   drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> >>>>> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> >>>>> new file mode 100644
> >>>>> index 0000000..d45417a
> >>>>> --- /dev/null
> >>>>> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> >>>>> @@ -0,0 +1,208 @@
> >>>>> +/*
> >>>>> + * Copyright (C) 2016 Noralf Trønnes
> >>>>> + *
> >>>>> + * This program is free software; you can redistribute it and/or modify
> >>>>> + * it under the terms of the GNU General Public License as published by
> >>>>> + * the Free Software Foundation; either version 2 of the License, or
> >>>>> + * (at your option) any later version.
> >>>>> + */
> >>>>> +
> >>>>> +#include <drm/drmP.h>
> >>>>> +#include <drm/drm_atomic.h>
> >>>>> +#include <drm/drm_atomic_helper.h>
> >>>>> +#include <drm/drm_crtc_helper.h>
> >>>>> +#include <drm/drm_plane_helper.h>
> >>>>> +#include <drm/drm_simple_kms_helper.h>
> >>>>> +#include <linux/slab.h>
> >>>>> +
> >>>>> +/**
> >>>>> + * DOC: overview
> >>>>> + *
> >>>>> + * This helper library provides helpers for drivers for simple display
> >>>>> + * hardware.
> >>>>> + *
> >>>>> + * drm_simple_display_pipe_init() initializes a simple display pipeline
> >>>>> + * which has only one full-screen scanout buffer feeding one output. The
> >>>>> + * pipeline is represented by struct &drm_simple_display_pipe and binds
> >>>>> + * together &drm_plane, &drm_crtc and &drm_encoder structures into one fixed
> >>>>> + * entity. Some flexibility for code reuse is provided through a separately
> >>>>> + * allocated &drm_connector object and supporting optional &drm_bridge
> >>>>> + * encoder drivers.
> >>>>> + */
> >>>>> +
> >>>>> +static const struct drm_encoder_funcs drm_simple_kms_encoder_funcs = {
> >>>>> +	.destroy = drm_encoder_cleanup,
> >>>>> +};
> >>>>> +
> >>>>> +static void drm_simple_kms_crtc_enable(struct drm_crtc *crtc)
> >>>>> +{
> >>>>> +	struct drm_simple_display_pipe *pipe;
> >>>>> +
> >>>>> +	pipe = container_of(crtc, struct drm_simple_display_pipe, crtc);
> >>>>> +	if (!pipe->funcs || !pipe->funcs->enable)
> >>>>> +		return;
> >>>>> +
> >>>>> +	pipe->funcs->enable(pipe, crtc->state);
> >>>>> +}
> >>>>> +
> >>>>> +static void drm_simple_kms_crtc_disable(struct drm_crtc *crtc)
> >>>>> +{
> >>>>> +	struct drm_simple_display_pipe *pipe;
> >>>>> +
> >>>>> +	pipe = container_of(crtc, struct drm_simple_display_pipe, crtc);
> >>>>> +	if (!pipe->funcs || !pipe->funcs->disable)
> >>>>> +		return;
> >>>>> +
> >>>>> +	pipe->funcs->disable(pipe);
> >>>>> +}
> >>>>> +
> >>>>> +static const struct drm_crtc_helper_funcs drm_simple_kms_crtc_helper_funcs = {
> >>>>> +	.disable = drm_simple_kms_crtc_disable,
> >>>>> +	.enable = drm_simple_kms_crtc_enable,
> >>>>> +};
> >>>>> +
> >>>>> +static const struct drm_crtc_funcs drm_simple_kms_crtc_funcs = {
> >>>>> +	.reset = drm_atomic_helper_crtc_reset,
> >>>>> +	.destroy = drm_crtc_cleanup,
> >>>>> +	.set_config = drm_atomic_helper_set_config,
> >>>>> +	.page_flip = drm_atomic_helper_page_flip,
> >>>>> +	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
> >>>>> +	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
> >>>>> +};
> >>>>> +
> >>>>> +static int drm_simple_kms_plane_atomic_check(struct drm_plane *plane,
> >>>>> +					struct drm_plane_state *plane_state)
> >>>>> +{
> >>>>> +	struct drm_rect src = {
> >>>>> +		.x1 = plane_state->src_x,
> >>>>> +		.y1 = plane_state->src_y,
> >>>>> +		.x2 = plane_state->src_x + plane_state->src_w,
> >>>>> +		.y2 = plane_state->src_y + plane_state->src_h,
> >>>>> +	};
> >>>>> +	struct drm_rect dest = {
> >>>>> +		.x1 = plane_state->crtc_x,
> >>>>> +		.y1 = plane_state->crtc_y,
> >>>>> +		.x2 = plane_state->crtc_x + plane_state->crtc_w,
> >>>>> +		.y2 = plane_state->crtc_y + plane_state->crtc_h,
> >>>>> +	};
> >>>>> +	struct drm_rect clip = { 0 };
> >>>>> +	struct drm_simple_display_pipe *pipe;
> >>>>> +	struct drm_crtc_state *crtc_state;
> >>>>> +	bool visible;
> >>>>> +	int ret;
> >>>>> +
> >>>>> +	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> >>>>> +	crtc_state = drm_atomic_get_existing_crtc_state(plane_state->state,
> >>>>> +							&pipe->crtc);
> >>>>> +	if (crtc_state->enable != !!plane_state->crtc)
> >>>>> +		return -EINVAL; /* plane must match crtc enable state */
> >>>>> +
> >>>>> +	if (!crtc_state->enable)
> >>>>> +		return 0; /* nothing to check when disabling or disabled */
> >>>>> +
> >>>>> +	clip.x2 = crtc_state->adjusted_mode.hdisplay;
> >>>>> +	clip.y2 = crtc_state->adjusted_mode.vdisplay;
> >>>>> +	ret = drm_plane_helper_check_update(plane, &pipe->crtc,
> >>>>> +					    plane_state->fb,
> >>>>> +					    &src, &dest, &clip,
> >>>>> +					    DRM_PLANE_HELPER_NO_SCALING,
> >>>>> +					    DRM_PLANE_HELPER_NO_SCALING,
> >>>>> +					    false, true, &visible);
> >>>>> +	if (ret)
> >>>>> +		return ret;
> >>>>> +
> >>>>> +	if (!visible)
> >>>>> +		return -EINVAL;
> >>>>> +
> >>>>> +	if (!pipe->funcs || !pipe->funcs->check)
> >>>>> +		return 0;
> >>>>> +
> >>>>> +	return pipe->funcs->check(pipe, plane_state, crtc_state);
> >>>>> +}
> >>>> What's anyone supposed to do with this when the clipped coordinates
> >>>> aren't even passed/stored anywhere?
> >>> It disallows positioning and scaling, so shouldn't ever need to have the
> >>> clipped area?
> >> You can still configure a larger area that gets clipped to the
> >> fullscreen dimensions.
> > Oh right. Noralf, sounds like we need to feed back the clipped rectangle.
> > Probably best if we add clipped plane coordinates to drm_plane_state.
> 
> Both src and crtc or only src?
> 
>       if (!visible)
>           return -EINVAL;
> +
> +    plane_state->src_x = src.x1;
> +    plane_state->src_y = src.y1;
> +    plane_state->src_w = drm_rect_width(&src);
> +    plane_state->src_h = drm_rect_height(&src);
> +
> +    plane_state->crtc_x = dest.x1;
> +    plane_state->crtc_y = dest.y1;
> +    plane_state->crtc_w = drm_rect_width(&dest);
> +    plane_state->crtc_h = drm_rect_height(&dest);

You aren't allowed clobber the user provided coordinates like this.
What you need to do is store the clipped coordinates in the plane
state in addition to the user coordinates.

> 
>      if (!pipe->funcs || !pipe->funcs->check)
>          return 0;
> 
> Noralf.

-- 
Ville Syrjälä
Intel OTC