drm/i915/fbdev: Restore physical addresses for fb_mmap()

fbdev uses the physical address of our framebuffer for its fb_mmap()
routine. While we need to adapt this address for the new io BAR, we have
to fix v5.4 first! The simplest fix is to restore the smem back to v5.3
and we will then probably have to implement our fbops->fb_mmap() callback
to handle local memory.
Reported-by: Neil MacLeod <freedesktop@nmacleod.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112256
Fixes: 5f889b9a ("drm/i915: Disregard drm_mode_config.fb_base")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Tested-by: Neil MacLeod <freedesktop@nmacleod.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191113180633.3947-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/display/intel_fbdev.c

@@ -234,6 +234,11 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	info->apertures->ranges[0].base = ggtt->gmadr.start;
 	info->apertures->ranges[0].size = ggtt->mappable_end;
 
+	/* Our framebuffer is the entirety of fbdev's system memory */
+	info->fix.smem_start =
+		(unsigned long)(ggtt->gmadr.start + vma->node.start);
+	info->fix.smem_len = vma->node.size;
+
 	vaddr = i915_vma_pin_iomap(vma);
 	if (IS_ERR(vaddr)) {
 		DRM_ERROR("Failed to remap framebuffer into virtual memory\n");
@@ -243,10 +248,6 @@ static int intelfb_create(struct drm_fb_helper *helper,
 	info->screen_base = vaddr;
 	info->screen_size = vma->node.size;
 
-	/* Our framebuffer is the entirety of fbdev's system memory */
-	info->fix.smem_start = (unsigned long)info->screen_base;
-	info->fix.smem_len = info->screen_size;
-
 	drm_fb_helper_fill_info(info, &ifbdev->helper, sizes);
 
 	/* If the object is shmemfs backed, it will have given us zeroed pages.