drm/gma500: Implement client-based fbdev emulation

Implement fbdevemulation on top of struct drm_client and its helpers.
This ad-hoc interfaces for restoring and closing fbdev emulation with
per-client callback for hotplugging, restoring and unregistering.

A single function, psb_fbdev_setup(), starts fbdev emulation after
the DRM device has been registered. Hence, fbdev acts like a regular
DRM client.

The setup call only prepares the fbdev emulation. It then implements
connector hotplugging. The first successful hotplug event initializes
fbdev emulation.

Unregistering depends on the hotplugging. Fully initialized emulation
is cleaned up through drm_fb_helper_unregister_info() and fb_destroy.
For prepared-only setups, unregistering unprepares the emulation and
releases all resources. In both cases, fbdev emulation will be cleaned
up.

v2:
	* declare empty setup function as 'static inline' (kernel
	  test robot)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230313151610.14367-7-tzimmermann@suse.de

drivers/gpu/drm/gma500/fbdev.c

@@ -8,6 +8,7 @@
 #include <linux/pfn_t.h>
 
 #include <drm/drm_crtc_helper.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_framebuffer.h>
 
@@ -121,6 +122,27 @@ static int psb_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 	return 0;
 }
 
+static void psb_fbdev_fb_destroy(struct fb_info *info)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	struct drm_framebuffer *fb = fb_helper->fb;
+	struct drm_gem_object *obj = fb->obj[0];
+
+	drm_fb_helper_fini(fb_helper);
+
+	drm_framebuffer_unregister_private(fb);
+	fb->obj[0] = NULL;
+	drm_framebuffer_cleanup(fb);
+	kfree(fb);
+
+	drm_gem_object_put(obj);
+
+	drm_client_release(&fb_helper->client);
+
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+}
+
 static const struct fb_ops psb_fbdev_fb_ops = {
 	.owner = THIS_MODULE,
 	DRM_FB_HELPER_DEFAULT_OPS,
@@ -131,6 +153,7 @@ static const struct fb_ops psb_fbdev_fb_ops = {
 	.fb_copyarea = drm_fb_helper_cfb_copyarea,
 	.fb_imageblit = drm_fb_helper_cfb_imageblit,
 	.fb_mmap = psb_fbdev_fb_mmap,
+	.fb_destroy = psb_fbdev_fb_destroy,
 };
 
 /*
@@ -190,14 +213,6 @@ static int psb_fbdev_fb_probe(struct drm_fb_helper *fb_helper,
 		return PTR_ERR(backing);
 	obj = &backing->base;
 
-	memset(dev_priv->vram_addr + backing->offset, 0, size);
-
-	info = drm_fb_helper_alloc_info(fb_helper);
-	if (IS_ERR(info)) {
-		ret = PTR_ERR(info);
-		goto err_drm_gem_object_put;
-	}
-
 	fb = psb_framebuffer_create(dev, &mode_cmd, obj);
 	if (IS_ERR(fb)) {
 		ret = PTR_ERR(fb);
@@ -206,28 +221,40 @@ static int psb_fbdev_fb_probe(struct drm_fb_helper *fb_helper,
 
 	fb_helper->fb = fb;
 
-	info->fbops = &psb_fbdev_fb_ops;
-
-	info->fix.smem_start = dev_priv->fb_base;
-	info->fix.smem_len = size;
-	info->fix.ywrapstep = 0;
-	info->fix.ypanstep = 0;
+	info = drm_fb_helper_alloc_info(fb_helper);
+	if (IS_ERR(info)) {
+		ret = PTR_ERR(info);
+		goto err_drm_framebuffer_unregister_private;
+	}
 
+	info->fbops = &psb_fbdev_fb_ops;
+	info->flags = FBINFO_DEFAULT;
 	/* Accessed stolen memory directly */
 	info->screen_base = dev_priv->vram_addr + backing->offset;
 	info->screen_size = size;
 
 	drm_fb_helper_fill_info(info, fb_helper, sizes);
 
+	info->fix.smem_start = dev_priv->fb_base;
+	info->fix.smem_len = size;
+	info->fix.ywrapstep = 0;
+	info->fix.ypanstep = 0;
 	info->fix.mmio_start = pci_resource_start(pdev, 0);
 	info->fix.mmio_len = pci_resource_len(pdev, 0);
 
+	memset(info->screen_base, 0, info->screen_size);
+
 	/* Use default scratch pixmap (info->pixmap.flags = FB_PIXMAP_SYSTEM) */
 
 	dev_dbg(dev->dev, "allocated %dx%d fb\n", fb->width, fb->height);
 
 	return 0;
 
+err_drm_framebuffer_unregister_private:
+	drm_framebuffer_unregister_private(fb);
+	fb->obj[0] = NULL;
+	drm_framebuffer_cleanup(fb);
+	kfree(fb);
 err_drm_gem_object_put:
 	drm_gem_object_put(obj);
 	return ret;
@@ -237,68 +264,92 @@ static const struct drm_fb_helper_funcs psb_fbdev_fb_helper_funcs = {
 	.fb_probe = psb_fbdev_fb_probe,
 };
 
-static int psb_fbdev_destroy(struct drm_device *dev,
-			     struct drm_fb_helper *fb_helper)
-{
-	struct drm_framebuffer *fb = fb_helper->fb;
-
-	drm_fb_helper_unregister_info(fb_helper);
+/*
+ * struct drm_client_funcs and setup code
+ */
 
-	drm_fb_helper_fini(fb_helper);
-	drm_framebuffer_unregister_private(fb);
-	drm_framebuffer_cleanup(fb);
+static void psb_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_fb_helper_unprepare(fb_helper);
+		drm_client_release(&fb_helper->client);
+		kfree(fb_helper);
+	}
+}
 
-	if (fb->obj[0])
-		drm_gem_object_put(fb->obj[0]);
-	kfree(fb);
+static int psb_fbdev_client_restore(struct drm_client_dev *client)
+{
+	drm_fb_helper_lastclose(client->dev);
 
 	return 0;
 }
 
-int psb_fbdev_init(struct drm_device *dev)
+static int psb_fbdev_client_hotplug(struct drm_client_dev *client)
 {
-	struct drm_fb_helper *fb_helper;
-	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+	struct drm_device *dev = client->dev;
 	int ret;
 
-	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
-	if (!fb_helper)
-		return -ENOMEM;
-
-	dev_priv->fb_helper = fb_helper;
-
-	drm_fb_helper_prepare(dev, fb_helper, 32, &psb_fbdev_fb_helper_funcs);
+	if (dev->fb_helper)
+		return drm_fb_helper_hotplug_event(dev->fb_helper);
 
 	ret = drm_fb_helper_init(dev, fb_helper);
 	if (ret)
-		goto free;
+		goto err_drm_err;
 
-	/* disable all the possible outputs/crtcs before entering KMS mode */
-	drm_helper_disable_unused_functions(dev);
+	if (!drm_drv_uses_atomic_modeset(dev))
+		drm_helper_disable_unused_functions(dev);
 
 	ret = drm_fb_helper_initial_config(fb_helper);
 	if (ret)
-		goto fini;
+		goto err_drm_fb_helper_fini;
 
 	return 0;
 
-fini:
+err_drm_fb_helper_fini:
 	drm_fb_helper_fini(fb_helper);
-free:
-	drm_fb_helper_unprepare(fb_helper);
-	kfree(fb_helper);
+err_drm_err:
+	drm_err(dev, "Failed to setup gma500 fbdev emulation (ret=%d)\n", ret);
 	return ret;
 }
 
-void psb_fbdev_fini(struct drm_device *dev)
+static const struct drm_client_funcs psb_fbdev_client_funcs = {
+	.owner		= THIS_MODULE,
+	.unregister	= psb_fbdev_client_unregister,
+	.restore	= psb_fbdev_client_restore,
+	.hotplug	= psb_fbdev_client_hotplug,
+};
+
+void psb_fbdev_setup(struct drm_psb_private *dev_priv)
 {
-	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
+	struct drm_device *dev = &dev_priv->dev;
+	struct drm_fb_helper *fb_helper;
+	int ret;
 
-	if (!dev_priv->fb_helper)
+	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
+	if (!fb_helper)
 		return;
+	drm_fb_helper_prepare(dev, fb_helper, 32, &psb_fbdev_fb_helper_funcs);
+
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev-gma500", &psb_fbdev_client_funcs);
+	if (ret) {
+		drm_err(dev, "Failed to register client: %d\n", ret);
+		goto err_drm_fb_helper_unprepare;
+	}
+
+	ret = psb_fbdev_client_hotplug(&fb_helper->client);
+	if (ret)
+		drm_dbg_kms(dev, "client hotplug ret=%d\n", ret);
+
+	drm_client_register(&fb_helper->client);
+
+	return;
 
-	psb_fbdev_destroy(dev, dev_priv->fb_helper);
-	drm_fb_helper_unprepare(dev_priv->fb_helper);
-	kfree(dev_priv->fb_helper);
-	dev_priv->fb_helper = NULL;
+err_drm_fb_helper_unprepare:
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
 }

drivers/gpu/drm/gma500/framebuffer.c

@@ -5,7 +5,6 @@
  *
  **************************************************************************/
 
-#include <drm/drm_fb_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_modeset_helper.h>
@@ -120,7 +119,6 @@ static struct drm_framebuffer *psb_user_framebuffer_create
 
 static const struct drm_mode_config_funcs psb_mode_funcs = {
 	.fb_create = psb_user_framebuffer_create,
-	.output_poll_changed = drm_fb_helper_output_poll_changed,
 };
 
 static void psb_setup_outputs(struct drm_device *dev)
@@ -223,6 +221,5 @@ void psb_modeset_cleanup(struct drm_device *dev)
 	struct drm_psb_private *dev_priv = to_drm_psb_private(dev);
 	if (dev_priv->modeset) {
 		drm_kms_helper_poll_fini(dev);
-		psb_fbdev_fini(dev);
 	}
 }

drivers/gpu/drm/gma500/psb_drv.c

@@ -21,7 +21,6 @@
 #include <drm/drm.h>
 #include <drm/drm_aperture.h>
 #include <drm/drm_drv.h>
-#include <drm/drm_fb_helper.h>
 #include <drm/drm_file.h>
 #include <drm/drm_ioctl.h>
 #include <drm/drm_pciids.h>
@@ -387,7 +386,6 @@ static int psb_driver_load(struct drm_device *dev, unsigned long flags)
 	dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
 
 	psb_modeset_init(dev);
-	psb_fbdev_init(dev);
 	drm_kms_helper_poll_init(dev);
 
 	/* Only add backlight support if we have LVDS or MIPI output */
@@ -452,6 +450,8 @@ static int psb_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (ret)
 		return ret;
 
+	psb_fbdev_setup(dev_priv);
+
 	return 0;
 }
 
@@ -477,7 +477,6 @@ static const struct file_operations psb_gem_fops = {
 
 static const struct drm_driver driver = {
 	.driver_features = DRIVER_MODESET | DRIVER_GEM,
-	.lastclose = drm_fb_helper_lastclose,
 
 	.num_ioctls = ARRAY_SIZE(psb_ioctls),
 

drivers/gpu/drm/gma500/psb_drv.h

@@ -193,8 +193,6 @@
 #define KSEL_BYPASS_25 6
 #define KSEL_BYPASS_83_100 7
 
-struct drm_fb_helper;
-
 struct opregion_header;
 struct opregion_acpi;
 struct opregion_swsci;
@@ -522,7 +520,6 @@ struct drm_psb_private {
 	uint32_t blc_adj1;
 	uint32_t blc_adj2;
 
-	struct drm_fb_helper *fb_helper;
 	resource_size_t fb_base;
 
 	bool dsr_enable;
@@ -618,14 +615,9 @@ struct drm_framebuffer *psb_framebuffer_create(struct drm_device *dev,
 
 /* fbdev */
 #if defined(CONFIG_DRM_FBDEV_EMULATION)
-extern int psb_fbdev_init(struct drm_device *dev);
-extern void psb_fbdev_fini(struct drm_device *dev);
+void psb_fbdev_setup(struct drm_psb_private *dev_priv);
 #else
-static inline int psb_fbdev_init(struct drm_device *dev)
-{
-	return 0;
-}
-static inline void psb_fbdev_fini(struct drm_device *dev)
+static inline void psb_fbdev_setup(struct drm_psb_private *dev_priv)
 { }
 #endif