linux-kernel - [PATCH 4/8] fbdev: sm712fb: fix boot screen glitch when sm712fb replaces VGA.

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Date:   Sun, 17 Mar 2019 06:25:00 +0800
From:   Yifeng Li <tomli@...li.me>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Teddy Wang <teddy.wang@...iconmotion.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Yifeng Li <tomli@...li.me>,
        stable@...r.kernel.org
Subject: [PATCH 4/8] 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@...li.me>
Cc: stable@...r.kernel.org  # v4.4+
---
 drivers/video/fbdev/sm712fb.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c
index 1a3d232c2916..e8149f0f47d5 100644
--- 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)
-- 
2.20.1