drm/fbdev: Add memory-agnostic fbdev client

[ Upstream commit 5d08c44e47b9d41366714552bdd374ac4b595591 ]

Add an fbdev client that can work with any memory manager. The
client implementation is the same as existing code in fbdev-dma or
fbdev-shmem.

Provide struct drm_driver.fbdev_probe for the new client to allocate
the surface GEM buffer. The new callback replaces fb_probe of struct
drm_fb_helper_funcs, which does the same.

To use the new client, DRM drivers set fbdev_probe in their struct
drm_driver instance and call drm_fbdev_client_setup(). Probing and
creating the fbdev surface buffer is now independent from the other
operations in struct drm_fb_helper. For the pixel format, the fbdev
client either uses a specified format, the value in preferred_depth
or 32-bit RGB.

v2:
- test for struct drm_fb_helper.funcs for NULL (Sui)
- respect struct drm_mode_config.preferred_depth for default format

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240924071734.98201-4-tzimmermann@suse.de
Stable-dep-of: 6b481ab0e685 ("drm/nouveau: select FW caching")
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 141 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_fbdev_client.c b/drivers/gpu/drm/drm_fbdev_client.c
new file mode 100644
index 000000000000..a09382afe2fb
--- /dev/null
+++ b/drivers/gpu/drm/drm_fbdev_client.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: MIT
+
+#include <drm/drm_client.h>
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fbdev_client.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_print.h>
+
+/*
+ * struct drm_client_funcs
+ */
+
+static void drm_fbdev_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_client_restore(struct drm_client_dev *client)
+{
+	drm_fb_helper_lastclose(client->dev);
+
+	return 0;
+}
+
+static int drm_fbdev_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_client_funcs = {
+	.owner		= THIS_MODULE,
+	.unregister	= drm_fbdev_client_unregister,
+	.restore	= drm_fbdev_client_restore,
+	.hotplug	= drm_fbdev_client_hotplug,
+};
+
+/**
+ * drm_fbdev_client_setup() - Setup fbdev emulation
+ * @dev: DRM device
+ * @format: Preferred color format for the device. DRM_FORMAT_XRGB8888
+ *          is used if this is zero.
+ *
+ * This function sets up fbdev emulation. 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().
+ *
+ * This function is safe to call even when there are no connectors present.
+ * Setup will be retried on the next hotplug event.
+ *
+ * The fbdev client is destroyed by drm_dev_unregister().
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
+ */
+int drm_fbdev_client_setup(struct drm_device *dev, const struct drm_format_info *format)
+{
+	struct drm_fb_helper *fb_helper;
+	unsigned int color_mode;
+	int ret;
+
+	/* TODO: Use format info throughout DRM */
+	if (format) {
+		unsigned int bpp = drm_format_info_bpp(format, 0);
+
+		switch (bpp) {
+		case 16:
+			color_mode = format->depth; // could also be 15
+			break;
+		default:
+			color_mode = bpp;
+		}
+	} else {
+		switch (dev->mode_config.preferred_depth) {
+		case 0:
+		case 24:
+			color_mode = 32;
+			break;
+		default:
+			color_mode = dev->mode_config.preferred_depth;
+		}
+	}
+
+	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 -ENOMEM;
+	drm_fb_helper_prepare(dev, fb_helper, color_mode, NULL);
+
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_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 0;
+
+err_drm_client_init:
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+	return ret;
+}
+EXPORT_SYMBOL(drm_fbdev_client_setup);