firmware: sysfb: Fix reference count of sysfb parent device

Retrieving the system framebuffer's parent device in sysfb_init()
increments the parent device's reference count. Hence release the
reference before leaving the init function.

Adding the sysfb platform device acquires and additional reference
for the parent. This keeps the parent device around while the system
framebuffer is in use.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 9eac534d ("firmware/sysfb: Set firmware-framebuffer parent device")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sui Jingfeng <suijingfeng@loongson.cn>
Cc: <stable@vger.kernel.org> # v6.9+
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240625081818.15696-1-tzimmermann@suse.de

drivers/firmware/sysfb.c

@@ -101,8 +101,10 @@ static __init struct device *sysfb_parent_dev(const struct screen_info *si)
 	if (IS_ERR(pdev)) {
 		return ERR_CAST(pdev);
 	} else if (pdev) {
-		if (!sysfb_pci_dev_is_enabled(pdev))
+		if (!sysfb_pci_dev_is_enabled(pdev)) {
+			pci_dev_put(pdev);
 			return ERR_PTR(-ENODEV);
+		}
 		return &pdev->dev;
 	}
 
@@ -137,7 +139,7 @@ static __init int sysfb_init(void)
 	if (compatible) {
 		pd = sysfb_create_simplefb(si, &mode, parent);
 		if (!IS_ERR(pd))
-			goto unlock_mutex;
+			goto put_device;
 	}
 
 	/* if the FB is incompatible, create a legacy framebuffer device */
@@ -155,7 +157,7 @@ static __init int sysfb_init(void)
 	pd = platform_device_alloc(name, 0);
 	if (!pd) {
 		ret = -ENOMEM;
-		goto unlock_mutex;
+		goto put_device;
 	}
 
 	pd->dev.parent = parent;
@@ -170,9 +172,11 @@ static __init int sysfb_init(void)
 	if (ret)
 		goto err;
 
-	goto unlock_mutex;
+	goto put_device;
 err:
 	platform_device_put(pd);
+put_device:
+	put_device(parent);
 unlock_mutex:
 	mutex_unlock(&disable_lock);
 	return ret;