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fbdev/atyfb: Fix DSP config on some PowerMacs & PowerBooks

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Since the complete re-write in 2.6.10, some PowerMacs (At least PowerMac 5500
and PowerMac G3 Beige rev A) with ATI Mach64 chip have suffered from unstable
columns in their framebuffer image. This seems to depend on a value (4) read
from PLL_EXT_CNTL register, which leads to incorrect DSP config parameters to
be written to the chip. This patch uses a value calculated by aty_init_pll_ct
instead, as a starting point.

There are questions as to whether this should be extended to other platforms
or maybe made dependent on specific chip types, but in the meantime, this has
been tested on various powermacs and works for them so let's commit it.

Signed-off-by: Risto Suominen <Risto.Suominen@gmail.com>
Tested-by: Michael Pettersson <mike@it.uu.se>
Cc: <stable@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Risto Suominen 2009-01-13 20:09:30 +00:00 committed by Benjamin Herrenschmidt
parent 59b608c2c3
commit 7fbb7cadd0
1 changed files with 11 additions and 0 deletions
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11
drivers/video/aty/mach64_ct.c
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@ -8,6 +8,9 @@
#include <asm/io.h>
#include <video/mach64.h>
#include "atyfb.h"
#ifdef CONFIG_PPC
#include <asm/machdep.h>
#endif
#undef DEBUG
@ -536,6 +539,14 @@ static int __devinit aty_init_pll_ct(const struct fb_info *info,
pll->ct.xclk_post_div_real = postdividers[xpost_div];
pll->ct.mclk_fb_div = q * pll->ct.xclk_post_div_real / 8;
#ifdef CONFIG_PPC
if (machine_is(powermac)) {
/* Override PLL_EXT_CNTL & 0x07. */
pll->ct.xclk_post_div = xpost_div;
pll->ct.xclk_ref_div = 1;
}
#endif
#ifdef DEBUG
pllmclk = (1000000 * pll->ct.mclk_fb_mult * pll->ct.mclk_fb_div) /
(par->ref_clk_per * pll->ct.pll_ref_div);