drm/fbdev-generic: Convert to fbdev-ttm

Only TTM-based drivers use fbdev-generic. Rename it to fbdev-ttm and
change the symbol infix from _generic_ to _ttm_. Link the source file
into TTM helpers, so that it is only build if TTM-based drivers have
been selected. Select DRM_TTM_HELPER for loongson.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-43-tzimmermann@suse.de

drivers/gpu/drm/drm_fbdev_ttm.c

@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: MIT
+
+#include <linux/moduleparam.h>
+#include <linux/vmalloc.h>
+
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_print.h>
+
+#include <drm/drm_fbdev_ttm.h>
+
+/* @user: 1=userspace, 0=fbcon */
+static int drm_fbdev_ttm_fb_open(struct fb_info *info, int user)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+
+	/* No need to take a ref for fbcon because it unbinds on unregister */
+	if (user && !try_module_get(fb_helper->dev->driver->fops->owner))
+		return -ENODEV;
+
+	return 0;
+}
+
+static int drm_fbdev_ttm_fb_release(struct fb_info *info, int user)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+
+	if (user)
+		module_put(fb_helper->dev->driver->fops->owner);
+
+	return 0;
+}
+
+FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_ttm,
+				   drm_fb_helper_damage_range,
+				   drm_fb_helper_damage_area);
+
+static void drm_fbdev_ttm_fb_destroy(struct fb_info *info)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	void *shadow = info->screen_buffer;
+
+	if (!fb_helper->dev)
+		return;
+
+	fb_deferred_io_cleanup(info);
+	drm_fb_helper_fini(fb_helper);
+	vfree(shadow);
+	drm_client_framebuffer_delete(fb_helper->buffer);
+
+	drm_client_release(&fb_helper->client);
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+}
+
+static const struct fb_ops drm_fbdev_ttm_fb_ops = {
+	.owner		= THIS_MODULE,
+	.fb_open	= drm_fbdev_ttm_fb_open,
+	.fb_release	= drm_fbdev_ttm_fb_release,
+	FB_DEFAULT_DEFERRED_OPS(drm_fbdev_ttm),
+	DRM_FB_HELPER_DEFAULT_OPS,
+	.fb_destroy	= drm_fbdev_ttm_fb_destroy,
+};
+
+/*
+ * This function uses the client API to create a framebuffer backed by a dumb buffer.
+ */
+static int drm_fbdev_ttm_helper_fb_probe(struct drm_fb_helper *fb_helper,
+					     struct drm_fb_helper_surface_size *sizes)
+{
+	struct drm_client_dev *client = &fb_helper->client;
+	struct drm_device *dev = fb_helper->dev;
+	struct drm_client_buffer *buffer;
+	struct fb_info *info;
+	size_t screen_size;
+	void *screen_buffer;
+	u32 format;
+	int ret;
+
+	drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
+		    sizes->surface_width, sizes->surface_height,
+		    sizes->surface_bpp);
+
+	format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+	buffer = drm_client_framebuffer_create(client, sizes->surface_width,
+					       sizes->surface_height, format);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	fb_helper->buffer = buffer;
+	fb_helper->fb = buffer->fb;
+
+	screen_size = buffer->gem->size;
+	screen_buffer = vzalloc(screen_size);
+	if (!screen_buffer) {
+		ret = -ENOMEM;
+		goto err_drm_client_framebuffer_delete;
+	}
+
+	info = drm_fb_helper_alloc_info(fb_helper);
+	if (IS_ERR(info)) {
+		ret = PTR_ERR(info);
+		goto err_vfree;
+	}
+
+	drm_fb_helper_fill_info(info, fb_helper, sizes);
+
+	info->fbops = &drm_fbdev_ttm_fb_ops;
+
+	/* screen */
+	info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
+	info->screen_buffer = screen_buffer;
+	info->fix.smem_len = screen_size;
+
+	/* deferred I/O */
+	fb_helper->fbdefio.delay = HZ / 20;
+	fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;
+
+	info->fbdefio = &fb_helper->fbdefio;
+	ret = fb_deferred_io_init(info);
+	if (ret)
+		goto err_drm_fb_helper_release_info;
+
+	return 0;
+
+err_drm_fb_helper_release_info:
+	drm_fb_helper_release_info(fb_helper);
+err_vfree:
+	vfree(screen_buffer);
+err_drm_client_framebuffer_delete:
+	fb_helper->fb = NULL;
+	fb_helper->buffer = NULL;
+	drm_client_framebuffer_delete(buffer);
+	return ret;
+}
+
+static void drm_fbdev_ttm_damage_blit_real(struct drm_fb_helper *fb_helper,
+					   struct drm_clip_rect *clip,
+					   struct iosys_map *dst)
+{
+	struct drm_framebuffer *fb = fb_helper->fb;
+	size_t offset = clip->y1 * fb->pitches[0];
+	size_t len = clip->x2 - clip->x1;
+	unsigned int y;
+	void *src;
+
+	switch (drm_format_info_bpp(fb->format, 0)) {
+	case 1:
+		offset += clip->x1 / 8;
+		len = DIV_ROUND_UP(len + clip->x1 % 8, 8);
+		break;
+	case 2:
+		offset += clip->x1 / 4;
+		len = DIV_ROUND_UP(len + clip->x1 % 4, 4);
+		break;
+	case 4:
+		offset += clip->x1 / 2;
+		len = DIV_ROUND_UP(len + clip->x1 % 2, 2);
+		break;
+	default:
+		offset += clip->x1 * fb->format->cpp[0];
+		len *= fb->format->cpp[0];
+		break;
+	}
+
+	src = fb_helper->info->screen_buffer + offset;
+	iosys_map_incr(dst, offset); /* go to first pixel within clip rect */
+
+	for (y = clip->y1; y < clip->y2; y++) {
+		iosys_map_memcpy_to(dst, 0, src, len);
+		iosys_map_incr(dst, fb->pitches[0]);
+		src += fb->pitches[0];
+	}
+}
+
+static int drm_fbdev_ttm_damage_blit(struct drm_fb_helper *fb_helper,
+				     struct drm_clip_rect *clip)
+{
+	struct drm_client_buffer *buffer = fb_helper->buffer;
+	struct iosys_map map, dst;
+	int ret;
+
+	/*
+	 * We have to pin the client buffer to its current location while
+	 * flushing the shadow buffer. In the general case, concurrent
+	 * modesetting operations could try to move the buffer and would
+	 * fail. The modeset has to be serialized by acquiring the reservation
+	 * object of the underlying BO here.
+	 *
+	 * For fbdev emulation, we only have to protect against fbdev modeset
+	 * operations. Nothing else will involve the client buffer's BO. So it
+	 * is sufficient to acquire struct drm_fb_helper.lock here.
+	 */
+	mutex_lock(&fb_helper->lock);
+
+	ret = drm_client_buffer_vmap_local(buffer, &map);
+	if (ret)
+		goto out;
+
+	dst = map;
+	drm_fbdev_ttm_damage_blit_real(fb_helper, clip, &dst);
+
+	drm_client_buffer_vunmap_local(buffer);
+
+out:
+	mutex_unlock(&fb_helper->lock);
+
+	return ret;
+}
+
+static int drm_fbdev_ttm_helper_fb_dirty(struct drm_fb_helper *helper,
+					 struct drm_clip_rect *clip)
+{
+	struct drm_device *dev = helper->dev;
+	int ret;
+
+	/* Call damage handlers only if necessary */
+	if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
+		return 0;
+
+	ret = drm_fbdev_ttm_damage_blit(helper, clip);
+	if (drm_WARN_ONCE(dev, ret, "Damage blitter failed: ret=%d\n", ret))
+		return ret;
+
+	if (helper->fb->funcs->dirty) {
+		ret = helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
+		if (drm_WARN_ONCE(dev, ret, "Dirty helper failed: ret=%d\n", ret))
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct drm_fb_helper_funcs drm_fbdev_ttm_helper_funcs = {
+	.fb_probe = drm_fbdev_ttm_helper_fb_probe,
+	.fb_dirty = drm_fbdev_ttm_helper_fb_dirty,
+};
+
+static void drm_fbdev_ttm_client_unregister(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	if (fb_helper->info) {
+		drm_fb_helper_unregister_info(fb_helper);
+	} else {
+		drm_client_release(&fb_helper->client);
+		drm_fb_helper_unprepare(fb_helper);
+		kfree(fb_helper);
+	}
+}
+
+static int drm_fbdev_ttm_client_restore(struct drm_client_dev *client)
+{
+	drm_fb_helper_lastclose(client->dev);
+
+	return 0;
+}
+
+static int drm_fbdev_ttm_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+	struct drm_device *dev = client->dev;
+	int ret;
+
+	if (dev->fb_helper)
+		return drm_fb_helper_hotplug_event(dev->fb_helper);
+
+	ret = drm_fb_helper_init(dev, fb_helper);
+	if (ret)
+		goto err_drm_err;
+
+	if (!drm_drv_uses_atomic_modeset(dev))
+		drm_helper_disable_unused_functions(dev);
+
+	ret = drm_fb_helper_initial_config(fb_helper);
+	if (ret)
+		goto err_drm_fb_helper_fini;
+
+	return 0;
+
+err_drm_fb_helper_fini:
+	drm_fb_helper_fini(fb_helper);
+err_drm_err:
+	drm_err(dev, "fbdev: Failed to setup emulation (ret=%d)\n", ret);
+	return ret;
+}
+
+static const struct drm_client_funcs drm_fbdev_ttm_client_funcs = {
+	.owner		= THIS_MODULE,
+	.unregister	= drm_fbdev_ttm_client_unregister,
+	.restore	= drm_fbdev_ttm_client_restore,
+	.hotplug	= drm_fbdev_ttm_client_hotplug,
+};
+
+/**
+ * drm_fbdev_ttm_setup() - Setup fbdev emulation for TTM-based drivers
+ * @dev: DRM device
+ * @preferred_bpp: Preferred bits per pixel for the device.
+ *
+ * This function sets up fbdev emulation for TTM-based drivers that support
+ * dumb buffers with a virtual address and that can be mmap'ed.
+ * drm_fbdev_ttm_setup() shall be called after the DRM driver registered
+ * the new DRM device with drm_dev_register().
+ *
+ * Restore, hotplug events and teardown are all taken care of. Drivers that do
+ * suspend/resume need to call drm_fb_helper_set_suspend_unlocked() themselves.
+ * Simple drivers might use drm_mode_config_helper_suspend().
+ *
+ * In order to provide fixed mmap-able memory ranges, fbdev emulation
+ * uses a shadow buffer in system memory. The implementation blits the shadow
+ * fbdev buffer onto the real buffer in regular intervals.
+ *
+ * This function is safe to call even when there are no connectors present.
+ * Setup will be retried on the next hotplug event.
+ *
+ * The fbdev is destroyed by drm_dev_unregister().
+ */
+void drm_fbdev_ttm_setup(struct drm_device *dev, unsigned int preferred_bpp)
+{
+	struct drm_fb_helper *fb_helper;
+	int ret;
+
+	drm_WARN(dev, !dev->registered, "Device has not been registered.\n");
+	drm_WARN(dev, dev->fb_helper, "fb_helper is already set!\n");
+
+	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
+	if (!fb_helper)
+		return;
+	drm_fb_helper_prepare(dev, fb_helper, preferred_bpp, &drm_fbdev_ttm_helper_funcs);
+
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_ttm_client_funcs);
+	if (ret) {
+		drm_err(dev, "Failed to register client: %d\n", ret);
+		goto err_drm_client_init;
+	}
+
+	drm_client_register(&fb_helper->client);
+
+	return;
+
+err_drm_client_init:
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+	return;
+}
+EXPORT_SYMBOL(drm_fbdev_ttm_setup);