drm/fb-helper: Mark screen buffers in system memory with FBINFO_VIRTFB

Mark screen buffers in system memory with FBINFO_VIRTFB. Otherwise, fbdev
deferred I/O marks mmap'ed areas of system memory with VM_IO. (There's an
inverse relationship between the two flags.)

For shadow buffers, also set the FBINFO_READS_FAST hint.

v3:
	* change FB_ to FBINFO_ in commit description
v2:
	* updated commit description (Daniel)
	* added Fixes tag

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: d536540f304c ("drm/fb-helper: Add generic fbdev emulation .fb_probe function")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v4.19+
Link: https://patchwork.freedesktop.org/patch/msgid/20220201115305.9333-1-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 9727a59..805c5a6 100644 (file)
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2340,6 +2340,7 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
        fbi->fbops = &drm_fbdev_fb_ops;
        fbi->screen_size = sizes->surface_height * fb->pitches[0];
        fbi->fix.smem_len = fbi->screen_size;
+       fbi->flags = FBINFO_DEFAULT;
 
        drm_fb_helper_fill_info(fbi, fb_helper, sizes);
 
@@ -2347,19 +2348,21 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
                fbi->screen_buffer = vzalloc(fbi->screen_size);
                if (!fbi->screen_buffer)
                        return -ENOMEM;
+               fbi->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
 
                fbi->fbdefio = &drm_fbdev_defio;
-
                fb_deferred_io_init(fbi);
        } else {
                /* buffer is mapped for HW framebuffer */
                ret = drm_client_buffer_vmap(fb_helper->buffer, &map);
                if (ret)
                        return ret;
-               if (map.is_iomem)
+               if (map.is_iomem) {
                        fbi->screen_base = map.vaddr_iomem;
-               else
+               } else {
                        fbi->screen_buffer = map.vaddr;
+                       fbi->flags |= FBINFO_VIRTFB;
+               }
 
                /*
                 * Shamelessly leak the physical address to user-space. As