Message-ID: <20160530081050.GZ27098@phenom.ffwll.local>
Date:	Mon, 30 May 2016 10:10:50 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Noralf Trønnes <noralf@...nnes.org>
Cc:	dri-devel@...ts.freedesktop.org, daniel@...ll.ch,
	linux-kernel@...r.kernel.org, jsarha@...com
Subject: Re: [PATCH v4 3/3] drm: Add helper for simple display pipeline

On Sun, May 29, 2016 at 05:38:39PM +0200, Noralf Trønnes wrote:
> 
> Den 12.05.2016 20:25, skrev Noralf Trønnes:
> >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>
> >---
> 
> [...]
> 
> >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);
> >+}
> >+
> >+static void drm_simple_kms_plane_atomic_update(struct drm_plane *plane,
> >+					struct drm_plane_state *pstate)
> >+{
> >+	struct drm_simple_display_pipe *pipe;
> >+
> >+	pipe = container_of(plane, struct drm_simple_display_pipe, plane);
> >+	if (!pipe->funcs || !pipe->funcs->update)
> >+		return;
> >+
> >+	pipe->funcs->update(pipe, pstate);
> >+}
> >+
> >+static const struct drm_plane_helper_funcs drm_simple_kms_plane_helper_funcs = {
> >+	.atomic_check = drm_simple_kms_plane_atomic_check,
> >+	.atomic_update = drm_simple_kms_plane_atomic_update,
> >+};
> >+
> >+static const struct drm_plane_funcs drm_simple_kms_plane_funcs = {
> >+	.update_plane		= drm_atomic_helper_update_plane,
> >+	.disable_plane		= drm_atomic_helper_disable_plane,
> >+	.destroy		= drm_plane_cleanup,
> >+	.reset			= drm_atomic_helper_plane_reset,
> >+	.atomic_duplicate_state	= drm_atomic_helper_plane_duplicate_state,
> >+	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
> >+};
> >+
> >+/**
> >+ * drm_simple_display_pipe_init - Initialize a simple display pipeline
> >+ * @dev: DRM device
> >+ * @pipe: simple display pipe object to initialize
> >+ * @funcs: callbacks for the display pipe (optional)
> >+ * @formats: array of supported formats (%DRM_FORMAT_*)
> >+ * @format_count: number of elements in @formats
> >+ * @connector: connector to attach and register
> >+ *
> >+ * Sets up a display pipeline which consist of a really simple
> >+ * plane-crtc-encoder pipe coupled with the provided connector.
> >+ * Teardown of a simple display pipe is all handled automatically by the drm
> >+ * core through calling drm_mode_config_cleanup(). Drivers afterwards need to
> >+ * release the memory for the structure themselves.
> >+ *
> >+ * Returns:
> >+ * Zero on success, negative error code on failure.
> >+ */
> >+int drm_simple_display_pipe_init(struct drm_device *dev,
> >+			struct drm_simple_display_pipe *pipe,
> >+			const struct drm_simple_display_pipe_funcs *funcs,
> >+			const uint32_t *formats, unsigned int format_count,
> >+			struct drm_connector *connector)
> >+{
> >+	struct drm_encoder *encoder = &pipe->encoder;
> >+	struct drm_plane *plane = &pipe->plane;
> >+	struct drm_crtc *crtc = &pipe->crtc;
> >+	int ret;
> >+
> >+	pipe->funcs = funcs;
> >+
> >+	drm_plane_helper_add(plane, &drm_simple_kms_plane_helper_funcs);
> >+	ret = drm_universal_plane_init(dev, plane, 0,
> >+				       &drm_simple_kms_plane_funcs,
> >+				       formats, format_count,
> >+				       DRM_PLANE_TYPE_PRIMARY, NULL);
> >+	if (ret)
> >+		return ret;
> >+
> >+	drm_crtc_helper_add(crtc, &drm_simple_kms_crtc_helper_funcs);
> >+	ret = drm_crtc_init_with_planes(dev, crtc, plane, NULL,
> >+					&drm_simple_kms_crtc_funcs, NULL);
> >+	if (ret)
> >+		return ret;
> >+
> >+	encoder->possible_crtcs = 1 << drm_crtc_index(crtc);
> >+	ret = drm_encoder_init(dev, encoder, &drm_simple_kms_encoder_funcs,
> >+			       DRM_MODE_ENCODER_NONE, NULL);
> >+	if (ret)
> >+		return ret;
> >+
> >+	ret = drm_mode_connector_attach_encoder(connector, encoder);
> >+	if (ret)
> >+		return ret;
> >+
> >+	return drm_connector_register(connector);
> 
> I'm wondering if we shouldn't remove drm_connector_register() here,
> because it doesn't fit the pattern I've seen in the latest drivers:
> 
>         drm = drm_dev_alloc(...);
> 
>         /* init */
> 
>         ret = drm_dev_register(drm, 0);
>         ret = drm_connector_register_all(drm);

Excellent point, this should indeed be removed.
drm_simple_display_pipe_init should just wire up the connector to the
pipeline, not init/register it at all imo.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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