linux-kernel - [PATCH 4.4 075/241] fbdev: sm712fb: fix memory frequency by avoiding a switch/case fallthrough

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Date:   Sun,  9 Jun 2019 18:40:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
        Yifeng Li <tomli@...li.me>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [PATCH 4.4 075/241] fbdev: sm712fb: fix memory frequency by avoiding a switch/case fallthrough

From: Yifeng Li <tomli@...li.me>

commit 9dc20113988b9a75ea6b3abd68dc45e2d73ccdab upstream.

A fallthrough in switch/case was introduced in f627caf55b8e ("fbdev:
sm712fb: fix crashes and garbled display during DPMS modesetting"),
due to my copy-paste error, which would cause the memory clock frequency
for SM720 to be programmed to SM712.

Since it only reprograms the clock to a different frequency, it's only
a benign issue without visible side-effect, so it also evaded Sudip
Mukherjee's code review and regression tests. scripts/checkpatch.pl
also failed to discover the issue, possibly due to nested switch
statements.

This issue was found by Stephen Rothwell by building linux-next with
-Wimplicit-fallthrough.

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Fixes: f627caf55b8e ("fbdev: sm712fb: fix crashes and garbled display during DPMS modesetting")
Signed-off-by: Yifeng Li <tomli@...li.me>
Cc: Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc: Kees Cook <keescook@...omium.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/video/fbdev/sm712fb.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/video/fbdev/sm712fb.c
+++ b/drivers/video/fbdev/sm712fb.c
@@ -898,6 +898,7 @@ static int smtc_blank(int blank_mode, st
 		case 0x712:
 			smtc_seqw(0x6a, 0x16);
 			smtc_seqw(0x6b, 0x02);
+			break;
 		case 0x720:
 			smtc_seqw(0x6a, 0x0d);
 			smtc_seqw(0x6b, 0x02);