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    SubjectRe: [PATCH] atyfb: fix distorted image on PowerMacs
    Risto Suominen writes:
    > 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.
    >
    > Signed-off-by: Risto Suominen <Risto.Suominen@gmail.com>

    Thank you. I reported this issue way back in March 2005
    <http://marc.info/?l=linux-kernel&m=111175371705665&w=2>
    but nothing ever came out of that. Your patch applies
    cleanly to 2.6.29-rc2 and fixes the issue on my Beige G3.

    Tested-by: Mikael Pettersson <mikpe@it.uu.se>


    > ---
    > The testing is done on kernel version 2.6.18.
    >
    > --- a/drivers/video/aty/mach64_ct.c.org 2006-09-20 06:42:06.000000000 +0300
    > +++ b/drivers/video/aty/mach64_ct.c 2009-01-22 14:28:13.000000000 +0200
    > @@ -7,6 +7,7 @@
    > #include <linux/delay.h>
    > #include <asm/io.h>
    > #include <video/mach64.h>
    > +#include <asm/machdep.h>
    > #include "atyfb.h"
    > #undef DEBUG
    > @@ -536,6 +537,14 @@ static int __init aty_init_pll_ct(const
    > 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);
    > 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.
    >
    > Signed-off-by: Risto Suominen <Risto.Suominen@gmail.com>
    > ---
    > The testing is done on kernel version 2.6.18.
    >
    > --- a/drivers/video/aty/mach64_ct.c.org 2006-09-20 06:42:06.000000000 +0300
    > +++ b/drivers/video/aty/mach64_ct.c 2009-01-22 14:28:13.000000000 +0200
    > @@ -7,6 +7,7 @@
    > #include <linux/delay.h>
    > #include <asm/io.h>
    > #include <video/mach64.h>
    > +#include <asm/machdep.h>
    > #include "atyfb.h"
    >
    > #undef DEBUG
    > @@ -536,6 +537,14 @@ static int __init aty_init_pll_ct(const
    > 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);


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