Message-ID: <CAKMK7uH+o502SngA0t1nbfG9q0OtX8qV7Z2hKXfJMXKh6YbKeg@mail.gmail.com>
Date:	Tue, 17 May 2016 15:19:20 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:	Noralf Trønnes <noralf@...nnes.org>,
	Jyri Sarha <jsarha@...com>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] drm: Add helper for simple display pipeline

On Tue, May 17, 2016 at 3:14 PM, Ville Syrjälä
<ville.syrjala@...ux.intel.com> wrote:
> On Tue, May 17, 2016 at 03:04:52PM +0200, Daniel Vetter wrote:
>> 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?
>
> Basically everyone should use the clipped coords. There must be
> something very special going on if anyone wants to use the raw user
> coords.

Hm, maybe it would be better then to add raw_ versions, and clip to
src/dst in the atomic helpers for everyone? Or would that break some
drivers? This seems to get a bit out of hand ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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