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| author | Yifeng Li <tomli@tomli.me> | 2019-04-01 17:46:59 +0200 |
|---|---|---|
| committer | Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> | 2019-04-01 17:46:59 +0200 |
| commit | 9e0e59993df0601cddb95c4f6c61aa3d5e753c00 (patch) | |
| tree | fba9d9f33b69fcc61ac82dbd7022ce6f7970b168 /drivers/video/fbdev/sm712.h | |
| parent | ec1587d5073f29820e358f3a383850d61601d981 (diff) | |
| download | linux-stable-9e0e59993df0601cddb95c4f6c61aa3d5e753c00.tar.gz linux-stable-9e0e59993df0601cddb95c4f6c61aa3d5e753c00.tar.bz2 linux-stable-9e0e59993df0601cddb95c4f6c61aa3d5e753c00.zip | |
fbdev: sm712fb: fix crashes during framebuffer writes by correctly mapping VRAM
On a Thinkpad s30 (Pentium III / i440MX, Lynx3DM), running fbtest or X
will crash the machine instantly, because the VRAM/framebuffer is not
mapped correctly.
On SM712, the framebuffer starts at the beginning of address space, but
SM720's framebuffer starts at the 1 MiB offset from the beginning. However,
sm712fb fails to take this into account, as a result, writing to the
framebuffer will destroy all the registers and kill the system immediately.
Another problem is the driver assumes 8 MiB of VRAM for SM720, but some
SM720 system, such as this IBM Thinkpad, only has 4 MiB of VRAM.
Fix this problem by removing the hardcoded VRAM size, adding a function to
query the amount of VRAM from register MCR76 on SM720, and adding proper
framebuffer offset.
Please note that the memory map may have additional problems on Big-Endian
system, which is not available for testing by myself. But I highly suspect
that the original code is also broken on Big-Endian machines for SM720, so
at least we are not making the problem worse. More, the driver also assumed
SM710/SM712 has 4 MiB of VRAM, but it has a 2 MiB version as well, and used
in earlier laptops, such as IBM Thinkpad 240X, the driver would probably
crash on them. I've never seen one of those machines and cannot fix it, but
I have documented these problems in the comments.
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>
Diffstat (limited to 'drivers/video/fbdev/sm712.h')
| -rw-r--r-- | drivers/video/fbdev/sm712.h | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/drivers/video/fbdev/sm712.h b/drivers/video/fbdev/sm712.h index aad1cc4be34a..2cba1e73ed24 100644 --- a/drivers/video/fbdev/sm712.h +++ b/drivers/video/fbdev/sm712.h @@ -19,11 +19,6 @@ #define SCREEN_Y_RES 600 #define SCREEN_BPP 16 -/*Assume SM712 graphics chip has 4MB VRAM */ -#define SM712_VIDEOMEMORYSIZE 0x00400000 -/*Assume SM722 graphics chip has 8MB VRAM */ -#define SM722_VIDEOMEMORYSIZE 0x00800000 - #define dac_reg (0x3c8) #define dac_val (0x3c9) |