fbdev: sm712fb: fix boot screen glitch when sm712fb replaces VGA

When the machine is booted in VGA mode, loading sm712fb would cause
a glitch of random pixels shown on the screen. To prevent it from
happening, we first clear the entire framebuffer, and we also need
to stop calling smtcfb_setmode() during initialization, the fbdev
layer will call it for us later when it's ready.

Signed-off-by: Yifeng Li <tomli@tomli.me>
Tested-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Teddy Wang <teddy.wang@siliconmotion.com>
Cc: <stable@vger.kernel.org>  # v4.4+
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c
index 1a3d232..e8149f0 100644 (file)
--- a/drivers/video/fbdev/sm712fb.c
+++ b/drivers/video/fbdev/sm712fb.c
@@ -1493,7 +1493,11 @@ static int smtcfb_pci_probe(struct pci_dev *pdev,
        if (err)
                goto failed;
 
-       smtcfb_setmode(sfb);
+       /*
+        * The screen would be temporarily garbled when sm712fb takes over
+        * vesafb or VGA text mode. Zero the framebuffer.
+        */
+       memset_io(sfb->lfb, 0, sfb->fb->fix.smem_len);
 
        err = register_framebuffer(info);
        if (err < 0)