Date:	Tue, 17 May 2016 15:04:52 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Noralf Trønnes <noralf@...nnes.org>
Cc:	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>, Daniel Vetter <daniel@...ll.ch>,
	jsarha@...com, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] drm: Add helper for simple display pipeline

On Tue, May 17, 2016 at 02:22:26PM +0200, Noralf Trønnes wrote:
> 
> 
> Den 17.05.2016 14:12, skrev 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@...com
> >>>>>>>Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> >>>>>>>---
> >>>>>>>
> >>>>>>>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.
> 
> How do I do that?

Add new set of plane_state->clipped_src/dst_x/y/h/w I think, and suggest
to drivers to use that if they need clipped coordinates. I think at least,
all these clip rects are a bit too confusing to me. Ville?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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