[PATCH 4.4 057/241] fbdev: sm712fb: fix boot screen glitch when sm712fb replaces VGA

From: Greg Kroah-Hartman
Date: Sun Jun 09 2019 - 13:17:55 EST

From: Yifeng Li <tomli@xxxxxxxx>

commit ec1587d5073f29820e358f3a383850d61601d981 upstream.

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@xxxxxxxx>
Tested-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
Cc: Teddy Wang <teddy.wang@xxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.4+
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/video/fbdev/sm712fb.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/video/fbdev/sm712fb.c
+++ b/drivers/video/fbdev/sm712fb.c
@@ -1492,7 +1492,11 @@ static int smtcfb_pci_probe(struct pci_d
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)