tridentfb: Fix set_lwidth on TGUI9440 and CYBER9320

[firefly-linux-kernel-4.4.55.git] / drivers / video / fbdev / tridentfb.c

diff --git a/drivers/video/fbdev/tridentfb.c b/drivers/video/fbdev/tridentfb.c
index 742971304717d39dd192f1921e555b66460f320e..01b43e9ce941acb8751c0c2e8294e19db7ce927c 100644 (file)
--- a/drivers/video/fbdev/tridentfb.c
+++ b/drivers/video/fbdev/tridentfb.c
@@ -673,8 +673,14 @@ static int get_nativex(struct tridentfb_par *par)
 static inline void set_lwidth(struct tridentfb_par *par, int width)
 {
        write3X4(par, VGA_CRTC_OFFSET, width & 0xFF);
-       write3X4(par, AddColReg,
-                (read3X4(par, AddColReg) & 0xCF) | ((width & 0x300) >> 4));
+       /* chips older than TGUI9660 have only 1 width bit in AddColReg */
+       /* touching the other one breaks I2C/DDC */
+       if (par->chip_id == TGUI9440 || par->chip_id == CYBER9320)
+               write3X4(par, AddColReg,
+                    (read3X4(par, AddColReg) & 0xEF) | ((width & 0x100) >> 4));
+       else
+               write3X4(par, AddColReg,
+                    (read3X4(par, AddColReg) & 0xCF) | ((width & 0x300) >> 4));
 }
 
 /* For resolutions smaller than FP resolution stretch */